2867 lines
68 KiB
C
2867 lines
68 KiB
C
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/*
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* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
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*
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* This file is released under the GPL.
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*/
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#include <linux/blkdev.h>
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#include <linux/device-mapper.h>
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#include <linux/delay.h>
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/kdev_t.h>
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#include <linux/list.h>
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#include <linux/list_bl.h>
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#include <linux/mempool.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/log2.h>
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#include <linux/dm-kcopyd.h>
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#include "dm.h"
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#include "dm-exception-store.h"
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#define DM_MSG_PREFIX "snapshots"
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static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
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#define dm_target_is_snapshot_merge(ti) \
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((ti)->type->name == dm_snapshot_merge_target_name)
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/*
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* The size of the mempool used to track chunks in use.
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*/
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#define MIN_IOS 256
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#define DM_TRACKED_CHUNK_HASH_SIZE 16
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#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
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(DM_TRACKED_CHUNK_HASH_SIZE - 1))
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struct dm_exception_table {
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uint32_t hash_mask;
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unsigned int hash_shift;
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struct hlist_bl_head *table;
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};
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struct dm_snapshot {
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struct rw_semaphore lock;
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struct dm_dev *origin;
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struct dm_dev *cow;
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struct dm_target *ti;
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/* List of snapshots per Origin */
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struct list_head list;
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/*
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* You can't use a snapshot if this is 0 (e.g. if full).
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* A snapshot-merge target never clears this.
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*/
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int valid;
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/*
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* The snapshot overflowed because of a write to the snapshot device.
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* We don't have to invalidate the snapshot in this case, but we need
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* to prevent further writes.
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*/
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int snapshot_overflowed;
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/* Origin writes don't trigger exceptions until this is set */
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int active;
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atomic_t pending_exceptions_count;
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spinlock_t pe_allocation_lock;
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/* Protected by "pe_allocation_lock" */
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sector_t exception_start_sequence;
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/* Protected by kcopyd single-threaded callback */
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sector_t exception_complete_sequence;
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/*
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* A list of pending exceptions that completed out of order.
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* Protected by kcopyd single-threaded callback.
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*/
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struct rb_root out_of_order_tree;
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mempool_t pending_pool;
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struct dm_exception_table pending;
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struct dm_exception_table complete;
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/*
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* pe_lock protects all pending_exception operations and access
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* as well as the snapshot_bios list.
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*/
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spinlock_t pe_lock;
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/* Chunks with outstanding reads */
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spinlock_t tracked_chunk_lock;
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struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
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/* The on disk metadata handler */
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struct dm_exception_store *store;
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unsigned int in_progress;
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struct wait_queue_head in_progress_wait;
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struct dm_kcopyd_client *kcopyd_client;
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/* Wait for events based on state_bits */
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unsigned long state_bits;
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/* Range of chunks currently being merged. */
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chunk_t first_merging_chunk;
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int num_merging_chunks;
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/*
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* The merge operation failed if this flag is set.
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* Failure modes are handled as follows:
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* - I/O error reading the header
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* => don't load the target; abort.
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* - Header does not have "valid" flag set
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* => use the origin; forget about the snapshot.
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* - I/O error when reading exceptions
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* => don't load the target; abort.
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* (We can't use the intermediate origin state.)
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* - I/O error while merging
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* => stop merging; set merge_failed; process I/O normally.
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*/
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bool merge_failed:1;
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bool discard_zeroes_cow:1;
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bool discard_passdown_origin:1;
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/*
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* Incoming bios that overlap with chunks being merged must wait
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* for them to be committed.
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*/
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struct bio_list bios_queued_during_merge;
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};
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/*
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* state_bits:
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* RUNNING_MERGE - Merge operation is in progress.
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* SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
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* cleared afterwards.
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*/
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#define RUNNING_MERGE 0
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#define SHUTDOWN_MERGE 1
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/*
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* Maximum number of chunks being copied on write.
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*
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* The value was decided experimentally as a trade-off between memory
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* consumption, stalling the kernel's workqueues and maintaining a high enough
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* throughput.
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*/
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#define DEFAULT_COW_THRESHOLD 2048
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static unsigned int cow_threshold = DEFAULT_COW_THRESHOLD;
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module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644);
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MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write");
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DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
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"A percentage of time allocated for copy on write");
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struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
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{
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return s->origin;
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}
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EXPORT_SYMBOL(dm_snap_origin);
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struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
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{
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return s->cow;
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}
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EXPORT_SYMBOL(dm_snap_cow);
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static sector_t chunk_to_sector(struct dm_exception_store *store,
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chunk_t chunk)
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{
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return chunk << store->chunk_shift;
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}
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static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
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{
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/*
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* There is only ever one instance of a particular block
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* device so we can compare pointers safely.
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*/
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return lhs == rhs;
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}
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struct dm_snap_pending_exception {
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struct dm_exception e;
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/*
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* Origin buffers waiting for this to complete are held
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* in a bio list
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*/
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struct bio_list origin_bios;
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struct bio_list snapshot_bios;
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/* Pointer back to snapshot context */
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struct dm_snapshot *snap;
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/*
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* 1 indicates the exception has already been sent to
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* kcopyd.
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*/
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int started;
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/* There was copying error. */
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int copy_error;
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/* A sequence number, it is used for in-order completion. */
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sector_t exception_sequence;
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struct rb_node out_of_order_node;
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/*
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* For writing a complete chunk, bypassing the copy.
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*/
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struct bio *full_bio;
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bio_end_io_t *full_bio_end_io;
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};
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/*
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* Hash table mapping origin volumes to lists of snapshots and
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* a lock to protect it
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*/
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static struct kmem_cache *exception_cache;
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static struct kmem_cache *pending_cache;
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struct dm_snap_tracked_chunk {
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struct hlist_node node;
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chunk_t chunk;
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};
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static void init_tracked_chunk(struct bio *bio)
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{
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struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
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INIT_HLIST_NODE(&c->node);
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}
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static bool is_bio_tracked(struct bio *bio)
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{
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struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
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return !hlist_unhashed(&c->node);
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}
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static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
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{
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struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
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c->chunk = chunk;
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spin_lock_irq(&s->tracked_chunk_lock);
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hlist_add_head(&c->node,
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&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
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spin_unlock_irq(&s->tracked_chunk_lock);
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}
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static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
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{
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struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
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unsigned long flags;
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spin_lock_irqsave(&s->tracked_chunk_lock, flags);
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hlist_del(&c->node);
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spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
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}
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static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
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{
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struct dm_snap_tracked_chunk *c;
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int found = 0;
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spin_lock_irq(&s->tracked_chunk_lock);
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hlist_for_each_entry(c,
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&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
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if (c->chunk == chunk) {
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found = 1;
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break;
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}
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}
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spin_unlock_irq(&s->tracked_chunk_lock);
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return found;
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}
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/*
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* This conflicting I/O is extremely improbable in the caller,
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* so msleep(1) is sufficient and there is no need for a wait queue.
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*/
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static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
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{
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while (__chunk_is_tracked(s, chunk))
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msleep(1);
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}
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/*
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* One of these per registered origin, held in the snapshot_origins hash
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*/
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struct origin {
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/* The origin device */
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struct block_device *bdev;
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struct list_head hash_list;
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/* List of snapshots for this origin */
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struct list_head snapshots;
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};
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/*
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* This structure is allocated for each origin target
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*/
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struct dm_origin {
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struct dm_dev *dev;
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struct dm_target *ti;
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unsigned int split_boundary;
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struct list_head hash_list;
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};
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/*
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* Size of the hash table for origin volumes. If we make this
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* the size of the minors list then it should be nearly perfect
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*/
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#define ORIGIN_HASH_SIZE 256
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#define ORIGIN_MASK 0xFF
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static struct list_head *_origins;
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static struct list_head *_dm_origins;
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static struct rw_semaphore _origins_lock;
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static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
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static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
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static uint64_t _pending_exceptions_done_count;
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static int init_origin_hash(void)
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{
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int i;
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_origins = kmalloc_array(ORIGIN_HASH_SIZE, sizeof(struct list_head),
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GFP_KERNEL);
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if (!_origins) {
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DMERR("unable to allocate memory for _origins");
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return -ENOMEM;
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}
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for (i = 0; i < ORIGIN_HASH_SIZE; i++)
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INIT_LIST_HEAD(_origins + i);
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_dm_origins = kmalloc_array(ORIGIN_HASH_SIZE,
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sizeof(struct list_head),
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GFP_KERNEL);
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if (!_dm_origins) {
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DMERR("unable to allocate memory for _dm_origins");
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kfree(_origins);
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return -ENOMEM;
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}
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for (i = 0; i < ORIGIN_HASH_SIZE; i++)
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INIT_LIST_HEAD(_dm_origins + i);
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init_rwsem(&_origins_lock);
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return 0;
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}
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static void exit_origin_hash(void)
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{
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kfree(_origins);
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kfree(_dm_origins);
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}
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static unsigned int origin_hash(struct block_device *bdev)
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{
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return bdev->bd_dev & ORIGIN_MASK;
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}
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static struct origin *__lookup_origin(struct block_device *origin)
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{
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struct list_head *ol;
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struct origin *o;
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ol = &_origins[origin_hash(origin)];
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list_for_each_entry(o, ol, hash_list)
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if (bdev_equal(o->bdev, origin))
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return o;
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return NULL;
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}
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static void __insert_origin(struct origin *o)
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{
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struct list_head *sl = &_origins[origin_hash(o->bdev)];
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list_add_tail(&o->hash_list, sl);
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}
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static struct dm_origin *__lookup_dm_origin(struct block_device *origin)
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{
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struct list_head *ol;
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struct dm_origin *o;
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|
|
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ol = &_dm_origins[origin_hash(origin)];
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list_for_each_entry(o, ol, hash_list)
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if (bdev_equal(o->dev->bdev, origin))
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return o;
|
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|
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return NULL;
|
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}
|
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|
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static void __insert_dm_origin(struct dm_origin *o)
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{
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struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)];
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list_add_tail(&o->hash_list, sl);
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}
|
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|
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static void __remove_dm_origin(struct dm_origin *o)
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{
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|
list_del(&o->hash_list);
|
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|
}
|
||
|
|
||
|
/*
|
||
|
* _origins_lock must be held when calling this function.
|
||
|
* Returns number of snapshots registered using the supplied cow device, plus:
|
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|
* snap_src - a snapshot suitable for use as a source of exception handover
|
||
|
* snap_dest - a snapshot capable of receiving exception handover.
|
||
|
* snap_merge - an existing snapshot-merge target linked to the same origin.
|
||
|
* There can be at most one snapshot-merge target. The parameter is optional.
|
||
|
*
|
||
|
* Possible return values and states of snap_src and snap_dest.
|
||
|
* 0: NULL, NULL - first new snapshot
|
||
|
* 1: snap_src, NULL - normal snapshot
|
||
|
* 2: snap_src, snap_dest - waiting for handover
|
||
|
* 2: snap_src, NULL - handed over, waiting for old to be deleted
|
||
|
* 1: NULL, snap_dest - source got destroyed without handover
|
||
|
*/
|
||
|
static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
|
||
|
struct dm_snapshot **snap_src,
|
||
|
struct dm_snapshot **snap_dest,
|
||
|
struct dm_snapshot **snap_merge)
|
||
|
{
|
||
|
struct dm_snapshot *s;
|
||
|
struct origin *o;
|
||
|
int count = 0;
|
||
|
int active;
|
||
|
|
||
|
o = __lookup_origin(snap->origin->bdev);
|
||
|
if (!o)
|
||
|
goto out;
|
||
|
|
||
|
list_for_each_entry(s, &o->snapshots, list) {
|
||
|
if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
|
||
|
*snap_merge = s;
|
||
|
if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
|
||
|
continue;
|
||
|
|
||
|
down_read(&s->lock);
|
||
|
active = s->active;
|
||
|
up_read(&s->lock);
|
||
|
|
||
|
if (active) {
|
||
|
if (snap_src)
|
||
|
*snap_src = s;
|
||
|
} else if (snap_dest)
|
||
|
*snap_dest = s;
|
||
|
|
||
|
count++;
|
||
|
}
|
||
|
|
||
|
out:
|
||
|
return count;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* On success, returns 1 if this snapshot is a handover destination,
|
||
|
* otherwise returns 0.
|
||
|
*/
|
||
|
static int __validate_exception_handover(struct dm_snapshot *snap)
|
||
|
{
|
||
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
|
||
|
struct dm_snapshot *snap_merge = NULL;
|
||
|
|
||
|
/* Does snapshot need exceptions handed over to it? */
|
||
|
if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
|
||
|
&snap_merge) == 2) ||
|
||
|
snap_dest) {
|
||
|
snap->ti->error = "Snapshot cow pairing for exception table handover failed";
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* If no snap_src was found, snap cannot become a handover
|
||
|
* destination.
|
||
|
*/
|
||
|
if (!snap_src)
|
||
|
return 0;
|
||
|
|
||
|
/*
|
||
|
* Non-snapshot-merge handover?
|
||
|
*/
|
||
|
if (!dm_target_is_snapshot_merge(snap->ti))
|
||
|
return 1;
|
||
|
|
||
|
/*
|
||
|
* Do not allow more than one merging snapshot.
|
||
|
*/
|
||
|
if (snap_merge) {
|
||
|
snap->ti->error = "A snapshot is already merging.";
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
|
||
|
if (!snap_src->store->type->prepare_merge ||
|
||
|
!snap_src->store->type->commit_merge) {
|
||
|
snap->ti->error = "Snapshot exception store does not support snapshot-merge.";
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
|
||
|
return 1;
|
||
|
}
|
||
|
|
||
|
static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
|
||
|
{
|
||
|
struct dm_snapshot *l;
|
||
|
|
||
|
/* Sort the list according to chunk size, largest-first smallest-last */
|
||
|
list_for_each_entry(l, &o->snapshots, list)
|
||
|
if (l->store->chunk_size < s->store->chunk_size)
|
||
|
break;
|
||
|
list_add_tail(&s->list, &l->list);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Make a note of the snapshot and its origin so we can look it
|
||
|
* up when the origin has a write on it.
|
||
|
*
|
||
|
* Also validate snapshot exception store handovers.
|
||
|
* On success, returns 1 if this registration is a handover destination,
|
||
|
* otherwise returns 0.
|
||
|
*/
|
||
|
static int register_snapshot(struct dm_snapshot *snap)
|
||
|
{
|
||
|
struct origin *o, *new_o = NULL;
|
||
|
struct block_device *bdev = snap->origin->bdev;
|
||
|
int r = 0;
|
||
|
|
||
|
new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
|
||
|
if (!new_o)
|
||
|
return -ENOMEM;
|
||
|
|
||
|
down_write(&_origins_lock);
|
||
|
|
||
|
r = __validate_exception_handover(snap);
|
||
|
if (r < 0) {
|
||
|
kfree(new_o);
|
||
|
goto out;
|
||
|
}
|
||
|
|
||
|
o = __lookup_origin(bdev);
|
||
|
if (o)
|
||
|
kfree(new_o);
|
||
|
else {
|
||
|
/* New origin */
|
||
|
o = new_o;
|
||
|
|
||
|
/* Initialise the struct */
|
||
|
INIT_LIST_HEAD(&o->snapshots);
|
||
|
o->bdev = bdev;
|
||
|
|
||
|
__insert_origin(o);
|
||
|
}
|
||
|
|
||
|
__insert_snapshot(o, snap);
|
||
|
|
||
|
out:
|
||
|
up_write(&_origins_lock);
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Move snapshot to correct place in list according to chunk size.
|
||
|
*/
|
||
|
static void reregister_snapshot(struct dm_snapshot *s)
|
||
|
{
|
||
|
struct block_device *bdev = s->origin->bdev;
|
||
|
|
||
|
down_write(&_origins_lock);
|
||
|
|
||
|
list_del(&s->list);
|
||
|
__insert_snapshot(__lookup_origin(bdev), s);
|
||
|
|
||
|
up_write(&_origins_lock);
|
||
|
}
|
||
|
|
||
|
static void unregister_snapshot(struct dm_snapshot *s)
|
||
|
{
|
||
|
struct origin *o;
|
||
|
|
||
|
down_write(&_origins_lock);
|
||
|
o = __lookup_origin(s->origin->bdev);
|
||
|
|
||
|
list_del(&s->list);
|
||
|
if (o && list_empty(&o->snapshots)) {
|
||
|
list_del(&o->hash_list);
|
||
|
kfree(o);
|
||
|
}
|
||
|
|
||
|
up_write(&_origins_lock);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Implementation of the exception hash tables.
|
||
|
* The lowest hash_shift bits of the chunk number are ignored, allowing
|
||
|
* some consecutive chunks to be grouped together.
|
||
|
*/
|
||
|
static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk);
|
||
|
|
||
|
/* Lock to protect access to the completed and pending exception hash tables. */
|
||
|
struct dm_exception_table_lock {
|
||
|
struct hlist_bl_head *complete_slot;
|
||
|
struct hlist_bl_head *pending_slot;
|
||
|
};
|
||
|
|
||
|
static void dm_exception_table_lock_init(struct dm_snapshot *s, chunk_t chunk,
|
||
|
struct dm_exception_table_lock *lock)
|
||
|
{
|
||
|
struct dm_exception_table *complete = &s->complete;
|
||
|
struct dm_exception_table *pending = &s->pending;
|
||
|
|
||
|
lock->complete_slot = &complete->table[exception_hash(complete, chunk)];
|
||
|
lock->pending_slot = &pending->table[exception_hash(pending, chunk)];
|
||
|
}
|
||
|
|
||
|
static void dm_exception_table_lock(struct dm_exception_table_lock *lock)
|
||
|
{
|
||
|
hlist_bl_lock(lock->complete_slot);
|
||
|
hlist_bl_lock(lock->pending_slot);
|
||
|
}
|
||
|
|
||
|
static void dm_exception_table_unlock(struct dm_exception_table_lock *lock)
|
||
|
{
|
||
|
hlist_bl_unlock(lock->pending_slot);
|
||
|
hlist_bl_unlock(lock->complete_slot);
|
||
|
}
|
||
|
|
||
|
static int dm_exception_table_init(struct dm_exception_table *et,
|
||
|
uint32_t size, unsigned int hash_shift)
|
||
|
{
|
||
|
unsigned int i;
|
||
|
|
||
|
et->hash_shift = hash_shift;
|
||
|
et->hash_mask = size - 1;
|
||
|
et->table = kvmalloc_array(size, sizeof(struct hlist_bl_head),
|
||
|
GFP_KERNEL);
|
||
|
if (!et->table)
|
||
|
return -ENOMEM;
|
||
|
|
||
|
for (i = 0; i < size; i++)
|
||
|
INIT_HLIST_BL_HEAD(et->table + i);
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static void dm_exception_table_exit(struct dm_exception_table *et,
|
||
|
struct kmem_cache *mem)
|
||
|
{
|
||
|
struct hlist_bl_head *slot;
|
||
|
struct dm_exception *ex;
|
||
|
struct hlist_bl_node *pos, *n;
|
||
|
int i, size;
|
||
|
|
||
|
size = et->hash_mask + 1;
|
||
|
for (i = 0; i < size; i++) {
|
||
|
slot = et->table + i;
|
||
|
|
||
|
hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list)
|
||
|
kmem_cache_free(mem, ex);
|
||
|
}
|
||
|
|
||
|
kvfree(et->table);
|
||
|
}
|
||
|
|
||
|
static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
|
||
|
{
|
||
|
return (chunk >> et->hash_shift) & et->hash_mask;
|
||
|
}
|
||
|
|
||
|
static void dm_remove_exception(struct dm_exception *e)
|
||
|
{
|
||
|
hlist_bl_del(&e->hash_list);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Return the exception data for a sector, or NULL if not
|
||
|
* remapped.
|
||
|
*/
|
||
|
static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
|
||
|
chunk_t chunk)
|
||
|
{
|
||
|
struct hlist_bl_head *slot;
|
||
|
struct hlist_bl_node *pos;
|
||
|
struct dm_exception *e;
|
||
|
|
||
|
slot = &et->table[exception_hash(et, chunk)];
|
||
|
hlist_bl_for_each_entry(e, pos, slot, hash_list)
|
||
|
if (chunk >= e->old_chunk &&
|
||
|
chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
|
||
|
return e;
|
||
|
|
||
|
return NULL;
|
||
|
}
|
||
|
|
||
|
static struct dm_exception *alloc_completed_exception(gfp_t gfp)
|
||
|
{
|
||
|
struct dm_exception *e;
|
||
|
|
||
|
e = kmem_cache_alloc(exception_cache, gfp);
|
||
|
if (!e && gfp == GFP_NOIO)
|
||
|
e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
|
||
|
|
||
|
return e;
|
||
|
}
|
||
|
|
||
|
static void free_completed_exception(struct dm_exception *e)
|
||
|
{
|
||
|
kmem_cache_free(exception_cache, e);
|
||
|
}
|
||
|
|
||
|
static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
|
||
|
{
|
||
|
struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool,
|
||
|
GFP_NOIO);
|
||
|
|
||
|
atomic_inc(&s->pending_exceptions_count);
|
||
|
pe->snap = s;
|
||
|
|
||
|
return pe;
|
||
|
}
|
||
|
|
||
|
static void free_pending_exception(struct dm_snap_pending_exception *pe)
|
||
|
{
|
||
|
struct dm_snapshot *s = pe->snap;
|
||
|
|
||
|
mempool_free(pe, &s->pending_pool);
|
||
|
smp_mb__before_atomic();
|
||
|
atomic_dec(&s->pending_exceptions_count);
|
||
|
}
|
||
|
|
||
|
static void dm_insert_exception(struct dm_exception_table *eh,
|
||
|
struct dm_exception *new_e)
|
||
|
{
|
||
|
struct hlist_bl_head *l;
|
||
|
struct hlist_bl_node *pos;
|
||
|
struct dm_exception *e = NULL;
|
||
|
|
||
|
l = &eh->table[exception_hash(eh, new_e->old_chunk)];
|
||
|
|
||
|
/* Add immediately if this table doesn't support consecutive chunks */
|
||
|
if (!eh->hash_shift)
|
||
|
goto out;
|
||
|
|
||
|
/* List is ordered by old_chunk */
|
||
|
hlist_bl_for_each_entry(e, pos, l, hash_list) {
|
||
|
/* Insert after an existing chunk? */
|
||
|
if (new_e->old_chunk == (e->old_chunk +
|
||
|
dm_consecutive_chunk_count(e) + 1) &&
|
||
|
new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
|
||
|
dm_consecutive_chunk_count(e) + 1)) {
|
||
|
dm_consecutive_chunk_count_inc(e);
|
||
|
free_completed_exception(new_e);
|
||
|
return;
|
||
|
}
|
||
|
|
||
|
/* Insert before an existing chunk? */
|
||
|
if (new_e->old_chunk == (e->old_chunk - 1) &&
|
||
|
new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
|
||
|
dm_consecutive_chunk_count_inc(e);
|
||
|
e->old_chunk--;
|
||
|
e->new_chunk--;
|
||
|
free_completed_exception(new_e);
|
||
|
return;
|
||
|
}
|
||
|
|
||
|
if (new_e->old_chunk < e->old_chunk)
|
||
|
break;
|
||
|
}
|
||
|
|
||
|
out:
|
||
|
if (!e) {
|
||
|
/*
|
||
|
* Either the table doesn't support consecutive chunks or slot
|
||
|
* l is empty.
|
||
|
*/
|
||
|
hlist_bl_add_head(&new_e->hash_list, l);
|
||
|
} else if (new_e->old_chunk < e->old_chunk) {
|
||
|
/* Add before an existing exception */
|
||
|
hlist_bl_add_before(&new_e->hash_list, &e->hash_list);
|
||
|
} else {
|
||
|
/* Add to l's tail: e is the last exception in this slot */
|
||
|
hlist_bl_add_behind(&new_e->hash_list, &e->hash_list);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Callback used by the exception stores to load exceptions when
|
||
|
* initialising.
|
||
|
*/
|
||
|
static int dm_add_exception(void *context, chunk_t old, chunk_t new)
|
||
|
{
|
||
|
struct dm_exception_table_lock lock;
|
||
|
struct dm_snapshot *s = context;
|
||
|
struct dm_exception *e;
|
||
|
|
||
|
e = alloc_completed_exception(GFP_KERNEL);
|
||
|
if (!e)
|
||
|
return -ENOMEM;
|
||
|
|
||
|
e->old_chunk = old;
|
||
|
|
||
|
/* Consecutive_count is implicitly initialised to zero */
|
||
|
e->new_chunk = new;
|
||
|
|
||
|
/*
|
||
|
* Although there is no need to lock access to the exception tables
|
||
|
* here, if we don't then hlist_bl_add_head(), called by
|
||
|
* dm_insert_exception(), will complain about accessing the
|
||
|
* corresponding list without locking it first.
|
||
|
*/
|
||
|
dm_exception_table_lock_init(s, old, &lock);
|
||
|
|
||
|
dm_exception_table_lock(&lock);
|
||
|
dm_insert_exception(&s->complete, e);
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Return a minimum chunk size of all snapshots that have the specified origin.
|
||
|
* Return zero if the origin has no snapshots.
|
||
|
*/
|
||
|
static uint32_t __minimum_chunk_size(struct origin *o)
|
||
|
{
|
||
|
struct dm_snapshot *snap;
|
||
|
unsigned int chunk_size = rounddown_pow_of_two(UINT_MAX);
|
||
|
|
||
|
if (o)
|
||
|
list_for_each_entry(snap, &o->snapshots, list)
|
||
|
chunk_size = min_not_zero(chunk_size,
|
||
|
snap->store->chunk_size);
|
||
|
|
||
|
return (uint32_t) chunk_size;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Hard coded magic.
|
||
|
*/
|
||
|
static int calc_max_buckets(void)
|
||
|
{
|
||
|
/* use a fixed size of 2MB */
|
||
|
unsigned long mem = 2 * 1024 * 1024;
|
||
|
mem /= sizeof(struct hlist_bl_head);
|
||
|
|
||
|
return mem;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Allocate room for a suitable hash table.
|
||
|
*/
|
||
|
static int init_hash_tables(struct dm_snapshot *s)
|
||
|
{
|
||
|
sector_t hash_size, cow_dev_size, max_buckets;
|
||
|
|
||
|
/*
|
||
|
* Calculate based on the size of the original volume or
|
||
|
* the COW volume...
|
||
|
*/
|
||
|
cow_dev_size = get_dev_size(s->cow->bdev);
|
||
|
max_buckets = calc_max_buckets();
|
||
|
|
||
|
hash_size = cow_dev_size >> s->store->chunk_shift;
|
||
|
hash_size = min(hash_size, max_buckets);
|
||
|
|
||
|
if (hash_size < 64)
|
||
|
hash_size = 64;
|
||
|
hash_size = rounddown_pow_of_two(hash_size);
|
||
|
if (dm_exception_table_init(&s->complete, hash_size,
|
||
|
DM_CHUNK_CONSECUTIVE_BITS))
|
||
|
return -ENOMEM;
|
||
|
|
||
|
/*
|
||
|
* Allocate hash table for in-flight exceptions
|
||
|
* Make this smaller than the real hash table
|
||
|
*/
|
||
|
hash_size >>= 3;
|
||
|
if (hash_size < 64)
|
||
|
hash_size = 64;
|
||
|
|
||
|
if (dm_exception_table_init(&s->pending, hash_size, 0)) {
|
||
|
dm_exception_table_exit(&s->complete, exception_cache);
|
||
|
return -ENOMEM;
|
||
|
}
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static void merge_shutdown(struct dm_snapshot *s)
|
||
|
{
|
||
|
clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
|
||
|
smp_mb__after_atomic();
|
||
|
wake_up_bit(&s->state_bits, RUNNING_MERGE);
|
||
|
}
|
||
|
|
||
|
static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
|
||
|
{
|
||
|
s->first_merging_chunk = 0;
|
||
|
s->num_merging_chunks = 0;
|
||
|
|
||
|
return bio_list_get(&s->bios_queued_during_merge);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Remove one chunk from the index of completed exceptions.
|
||
|
*/
|
||
|
static int __remove_single_exception_chunk(struct dm_snapshot *s,
|
||
|
chunk_t old_chunk)
|
||
|
{
|
||
|
struct dm_exception *e;
|
||
|
|
||
|
e = dm_lookup_exception(&s->complete, old_chunk);
|
||
|
if (!e) {
|
||
|
DMERR("Corruption detected: exception for block %llu is on disk but not in memory",
|
||
|
(unsigned long long)old_chunk);
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* If this is the only chunk using this exception, remove exception.
|
||
|
*/
|
||
|
if (!dm_consecutive_chunk_count(e)) {
|
||
|
dm_remove_exception(e);
|
||
|
free_completed_exception(e);
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* The chunk may be either at the beginning or the end of a
|
||
|
* group of consecutive chunks - never in the middle. We are
|
||
|
* removing chunks in the opposite order to that in which they
|
||
|
* were added, so this should always be true.
|
||
|
* Decrement the consecutive chunk counter and adjust the
|
||
|
* starting point if necessary.
|
||
|
*/
|
||
|
if (old_chunk == e->old_chunk) {
|
||
|
e->old_chunk++;
|
||
|
e->new_chunk++;
|
||
|
} else if (old_chunk != e->old_chunk +
|
||
|
dm_consecutive_chunk_count(e)) {
|
||
|
DMERR("Attempt to merge block %llu from the middle of a chunk range [%llu - %llu]",
|
||
|
(unsigned long long)old_chunk,
|
||
|
(unsigned long long)e->old_chunk,
|
||
|
(unsigned long long)
|
||
|
e->old_chunk + dm_consecutive_chunk_count(e));
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
|
||
|
dm_consecutive_chunk_count_dec(e);
|
||
|
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
static void flush_bios(struct bio *bio);
|
||
|
|
||
|
static int remove_single_exception_chunk(struct dm_snapshot *s)
|
||
|
{
|
||
|
struct bio *b = NULL;
|
||
|
int r;
|
||
|
chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
|
||
|
|
||
|
down_write(&s->lock);
|
||
|
|
||
|
/*
|
||
|
* Process chunks (and associated exceptions) in reverse order
|
||
|
* so that dm_consecutive_chunk_count_dec() accounting works.
|
||
|
*/
|
||
|
do {
|
||
|
r = __remove_single_exception_chunk(s, old_chunk);
|
||
|
if (r)
|
||
|
goto out;
|
||
|
} while (old_chunk-- > s->first_merging_chunk);
|
||
|
|
||
|
b = __release_queued_bios_after_merge(s);
|
||
|
|
||
|
out:
|
||
|
up_write(&s->lock);
|
||
|
if (b)
|
||
|
flush_bios(b);
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
static int origin_write_extent(struct dm_snapshot *merging_snap,
|
||
|
sector_t sector, unsigned int chunk_size);
|
||
|
|
||
|
static void merge_callback(int read_err, unsigned long write_err,
|
||
|
void *context);
|
||
|
|
||
|
static uint64_t read_pending_exceptions_done_count(void)
|
||
|
{
|
||
|
uint64_t pending_exceptions_done;
|
||
|
|
||
|
spin_lock(&_pending_exceptions_done_spinlock);
|
||
|
pending_exceptions_done = _pending_exceptions_done_count;
|
||
|
spin_unlock(&_pending_exceptions_done_spinlock);
|
||
|
|
||
|
return pending_exceptions_done;
|
||
|
}
|
||
|
|
||
|
static void increment_pending_exceptions_done_count(void)
|
||
|
{
|
||
|
spin_lock(&_pending_exceptions_done_spinlock);
|
||
|
_pending_exceptions_done_count++;
|
||
|
spin_unlock(&_pending_exceptions_done_spinlock);
|
||
|
|
||
|
wake_up_all(&_pending_exceptions_done);
|
||
|
}
|
||
|
|
||
|
static void snapshot_merge_next_chunks(struct dm_snapshot *s)
|
||
|
{
|
||
|
int i, linear_chunks;
|
||
|
chunk_t old_chunk, new_chunk;
|
||
|
struct dm_io_region src, dest;
|
||
|
sector_t io_size;
|
||
|
uint64_t previous_count;
|
||
|
|
||
|
BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
|
||
|
if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
|
||
|
goto shut;
|
||
|
|
||
|
/*
|
||
|
* valid flag never changes during merge, so no lock required.
|
||
|
*/
|
||
|
if (!s->valid) {
|
||
|
DMERR("Snapshot is invalid: can't merge");
|
||
|
goto shut;
|
||
|
}
|
||
|
|
||
|
linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
|
||
|
&new_chunk);
|
||
|
if (linear_chunks <= 0) {
|
||
|
if (linear_chunks < 0) {
|
||
|
DMERR("Read error in exception store: shutting down merge");
|
||
|
down_write(&s->lock);
|
||
|
s->merge_failed = true;
|
||
|
up_write(&s->lock);
|
||
|
}
|
||
|
goto shut;
|
||
|
}
|
||
|
|
||
|
/* Adjust old_chunk and new_chunk to reflect start of linear region */
|
||
|
old_chunk = old_chunk + 1 - linear_chunks;
|
||
|
new_chunk = new_chunk + 1 - linear_chunks;
|
||
|
|
||
|
/*
|
||
|
* Use one (potentially large) I/O to copy all 'linear_chunks'
|
||
|
* from the exception store to the origin
|
||
|
*/
|
||
|
io_size = linear_chunks * s->store->chunk_size;
|
||
|
|
||
|
dest.bdev = s->origin->bdev;
|
||
|
dest.sector = chunk_to_sector(s->store, old_chunk);
|
||
|
dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
|
||
|
|
||
|
src.bdev = s->cow->bdev;
|
||
|
src.sector = chunk_to_sector(s->store, new_chunk);
|
||
|
src.count = dest.count;
|
||
|
|
||
|
/*
|
||
|
* Reallocate any exceptions needed in other snapshots then
|
||
|
* wait for the pending exceptions to complete.
|
||
|
* Each time any pending exception (globally on the system)
|
||
|
* completes we are woken and repeat the process to find out
|
||
|
* if we can proceed. While this may not seem a particularly
|
||
|
* efficient algorithm, it is not expected to have any
|
||
|
* significant impact on performance.
|
||
|
*/
|
||
|
previous_count = read_pending_exceptions_done_count();
|
||
|
while (origin_write_extent(s, dest.sector, io_size)) {
|
||
|
wait_event(_pending_exceptions_done,
|
||
|
(read_pending_exceptions_done_count() !=
|
||
|
previous_count));
|
||
|
/* Retry after the wait, until all exceptions are done. */
|
||
|
previous_count = read_pending_exceptions_done_count();
|
||
|
}
|
||
|
|
||
|
down_write(&s->lock);
|
||
|
s->first_merging_chunk = old_chunk;
|
||
|
s->num_merging_chunks = linear_chunks;
|
||
|
up_write(&s->lock);
|
||
|
|
||
|
/* Wait until writes to all 'linear_chunks' drain */
|
||
|
for (i = 0; i < linear_chunks; i++)
|
||
|
__check_for_conflicting_io(s, old_chunk + i);
|
||
|
|
||
|
dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
|
||
|
return;
|
||
|
|
||
|
shut:
|
||
|
merge_shutdown(s);
|
||
|
}
|
||
|
|
||
|
static void error_bios(struct bio *bio);
|
||
|
|
||
|
static void merge_callback(int read_err, unsigned long write_err, void *context)
|
||
|
{
|
||
|
struct dm_snapshot *s = context;
|
||
|
struct bio *b = NULL;
|
||
|
|
||
|
if (read_err || write_err) {
|
||
|
if (read_err)
|
||
|
DMERR("Read error: shutting down merge.");
|
||
|
else
|
||
|
DMERR("Write error: shutting down merge.");
|
||
|
goto shut;
|
||
|
}
|
||
|
|
||
|
if (blkdev_issue_flush(s->origin->bdev) < 0) {
|
||
|
DMERR("Flush after merge failed: shutting down merge");
|
||
|
goto shut;
|
||
|
}
|
||
|
|
||
|
if (s->store->type->commit_merge(s->store,
|
||
|
s->num_merging_chunks) < 0) {
|
||
|
DMERR("Write error in exception store: shutting down merge");
|
||
|
goto shut;
|
||
|
}
|
||
|
|
||
|
if (remove_single_exception_chunk(s) < 0)
|
||
|
goto shut;
|
||
|
|
||
|
snapshot_merge_next_chunks(s);
|
||
|
|
||
|
return;
|
||
|
|
||
|
shut:
|
||
|
down_write(&s->lock);
|
||
|
s->merge_failed = true;
|
||
|
b = __release_queued_bios_after_merge(s);
|
||
|
up_write(&s->lock);
|
||
|
error_bios(b);
|
||
|
|
||
|
merge_shutdown(s);
|
||
|
}
|
||
|
|
||
|
static void start_merge(struct dm_snapshot *s)
|
||
|
{
|
||
|
if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
|
||
|
snapshot_merge_next_chunks(s);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Stop the merging process and wait until it finishes.
|
||
|
*/
|
||
|
static void stop_merge(struct dm_snapshot *s)
|
||
|
{
|
||
|
set_bit(SHUTDOWN_MERGE, &s->state_bits);
|
||
|
wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE);
|
||
|
clear_bit(SHUTDOWN_MERGE, &s->state_bits);
|
||
|
}
|
||
|
|
||
|
static int parse_snapshot_features(struct dm_arg_set *as, struct dm_snapshot *s,
|
||
|
struct dm_target *ti)
|
||
|
{
|
||
|
int r;
|
||
|
unsigned int argc;
|
||
|
const char *arg_name;
|
||
|
|
||
|
static const struct dm_arg _args[] = {
|
||
|
{0, 2, "Invalid number of feature arguments"},
|
||
|
};
|
||
|
|
||
|
/*
|
||
|
* No feature arguments supplied.
|
||
|
*/
|
||
|
if (!as->argc)
|
||
|
return 0;
|
||
|
|
||
|
r = dm_read_arg_group(_args, as, &argc, &ti->error);
|
||
|
if (r)
|
||
|
return -EINVAL;
|
||
|
|
||
|
while (argc && !r) {
|
||
|
arg_name = dm_shift_arg(as);
|
||
|
argc--;
|
||
|
|
||
|
if (!strcasecmp(arg_name, "discard_zeroes_cow"))
|
||
|
s->discard_zeroes_cow = true;
|
||
|
|
||
|
else if (!strcasecmp(arg_name, "discard_passdown_origin"))
|
||
|
s->discard_passdown_origin = true;
|
||
|
|
||
|
else {
|
||
|
ti->error = "Unrecognised feature requested";
|
||
|
r = -EINVAL;
|
||
|
break;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
if (!s->discard_zeroes_cow && s->discard_passdown_origin) {
|
||
|
/*
|
||
|
* TODO: really these are disjoint.. but ti->num_discard_bios
|
||
|
* and dm_bio_get_target_bio_nr() require rigid constraints.
|
||
|
*/
|
||
|
ti->error = "discard_passdown_origin feature depends on discard_zeroes_cow";
|
||
|
r = -EINVAL;
|
||
|
}
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Construct a snapshot mapping:
|
||
|
* <origin_dev> <COW-dev> <p|po|n> <chunk-size> [<# feature args> [<arg>]*]
|
||
|
*/
|
||
|
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
|
||
|
{
|
||
|
struct dm_snapshot *s;
|
||
|
struct dm_arg_set as;
|
||
|
int i;
|
||
|
int r = -EINVAL;
|
||
|
char *origin_path, *cow_path;
|
||
|
dev_t origin_dev, cow_dev;
|
||
|
unsigned int args_used, num_flush_bios = 1;
|
||
|
fmode_t origin_mode = FMODE_READ;
|
||
|
|
||
|
if (argc < 4) {
|
||
|
ti->error = "requires 4 or more arguments";
|
||
|
r = -EINVAL;
|
||
|
goto bad;
|
||
|
}
|
||
|
|
||
|
if (dm_target_is_snapshot_merge(ti)) {
|
||
|
num_flush_bios = 2;
|
||
|
origin_mode = FMODE_WRITE;
|
||
|
}
|
||
|
|
||
|
s = kzalloc(sizeof(*s), GFP_KERNEL);
|
||
|
if (!s) {
|
||
|
ti->error = "Cannot allocate private snapshot structure";
|
||
|
r = -ENOMEM;
|
||
|
goto bad;
|
||
|
}
|
||
|
|
||
|
as.argc = argc;
|
||
|
as.argv = argv;
|
||
|
dm_consume_args(&as, 4);
|
||
|
r = parse_snapshot_features(&as, s, ti);
|
||
|
if (r)
|
||
|
goto bad_features;
|
||
|
|
||
|
origin_path = argv[0];
|
||
|
argv++;
|
||
|
argc--;
|
||
|
|
||
|
r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
|
||
|
if (r) {
|
||
|
ti->error = "Cannot get origin device";
|
||
|
goto bad_origin;
|
||
|
}
|
||
|
origin_dev = s->origin->bdev->bd_dev;
|
||
|
|
||
|
cow_path = argv[0];
|
||
|
argv++;
|
||
|
argc--;
|
||
|
|
||
|
cow_dev = dm_get_dev_t(cow_path);
|
||
|
if (cow_dev && cow_dev == origin_dev) {
|
||
|
ti->error = "COW device cannot be the same as origin device";
|
||
|
r = -EINVAL;
|
||
|
goto bad_cow;
|
||
|
}
|
||
|
|
||
|
r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
|
||
|
if (r) {
|
||
|
ti->error = "Cannot get COW device";
|
||
|
goto bad_cow;
|
||
|
}
|
||
|
|
||
|
r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
|
||
|
if (r) {
|
||
|
ti->error = "Couldn't create exception store";
|
||
|
r = -EINVAL;
|
||
|
goto bad_store;
|
||
|
}
|
||
|
|
||
|
argv += args_used;
|
||
|
argc -= args_used;
|
||
|
|
||
|
s->ti = ti;
|
||
|
s->valid = 1;
|
||
|
s->snapshot_overflowed = 0;
|
||
|
s->active = 0;
|
||
|
atomic_set(&s->pending_exceptions_count, 0);
|
||
|
spin_lock_init(&s->pe_allocation_lock);
|
||
|
s->exception_start_sequence = 0;
|
||
|
s->exception_complete_sequence = 0;
|
||
|
s->out_of_order_tree = RB_ROOT;
|
||
|
init_rwsem(&s->lock);
|
||
|
INIT_LIST_HEAD(&s->list);
|
||
|
spin_lock_init(&s->pe_lock);
|
||
|
s->state_bits = 0;
|
||
|
s->merge_failed = false;
|
||
|
s->first_merging_chunk = 0;
|
||
|
s->num_merging_chunks = 0;
|
||
|
bio_list_init(&s->bios_queued_during_merge);
|
||
|
|
||
|
/* Allocate hash table for COW data */
|
||
|
if (init_hash_tables(s)) {
|
||
|
ti->error = "Unable to allocate hash table space";
|
||
|
r = -ENOMEM;
|
||
|
goto bad_hash_tables;
|
||
|
}
|
||
|
|
||
|
init_waitqueue_head(&s->in_progress_wait);
|
||
|
|
||
|
s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
|
||
|
if (IS_ERR(s->kcopyd_client)) {
|
||
|
r = PTR_ERR(s->kcopyd_client);
|
||
|
ti->error = "Could not create kcopyd client";
|
||
|
goto bad_kcopyd;
|
||
|
}
|
||
|
|
||
|
r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);
|
||
|
if (r) {
|
||
|
ti->error = "Could not allocate mempool for pending exceptions";
|
||
|
goto bad_pending_pool;
|
||
|
}
|
||
|
|
||
|
for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
|
||
|
INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
|
||
|
|
||
|
spin_lock_init(&s->tracked_chunk_lock);
|
||
|
|
||
|
ti->private = s;
|
||
|
ti->num_flush_bios = num_flush_bios;
|
||
|
if (s->discard_zeroes_cow)
|
||
|
ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1);
|
||
|
ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);
|
||
|
|
||
|
/* Add snapshot to the list of snapshots for this origin */
|
||
|
/* Exceptions aren't triggered till snapshot_resume() is called */
|
||
|
r = register_snapshot(s);
|
||
|
if (r == -ENOMEM) {
|
||
|
ti->error = "Snapshot origin struct allocation failed";
|
||
|
goto bad_load_and_register;
|
||
|
} else if (r < 0) {
|
||
|
/* invalid handover, register_snapshot has set ti->error */
|
||
|
goto bad_load_and_register;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Metadata must only be loaded into one table at once, so skip this
|
||
|
* if metadata will be handed over during resume.
|
||
|
* Chunk size will be set during the handover - set it to zero to
|
||
|
* ensure it's ignored.
|
||
|
*/
|
||
|
if (r > 0) {
|
||
|
s->store->chunk_size = 0;
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
r = s->store->type->read_metadata(s->store, dm_add_exception,
|
||
|
(void *)s);
|
||
|
if (r < 0) {
|
||
|
ti->error = "Failed to read snapshot metadata";
|
||
|
goto bad_read_metadata;
|
||
|
} else if (r > 0) {
|
||
|
s->valid = 0;
|
||
|
DMWARN("Snapshot is marked invalid.");
|
||
|
}
|
||
|
|
||
|
if (!s->store->chunk_size) {
|
||
|
ti->error = "Chunk size not set";
|
||
|
r = -EINVAL;
|
||
|
goto bad_read_metadata;
|
||
|
}
|
||
|
|
||
|
r = dm_set_target_max_io_len(ti, s->store->chunk_size);
|
||
|
if (r)
|
||
|
goto bad_read_metadata;
|
||
|
|
||
|
return 0;
|
||
|
|
||
|
bad_read_metadata:
|
||
|
unregister_snapshot(s);
|
||
|
bad_load_and_register:
|
||
|
mempool_exit(&s->pending_pool);
|
||
|
bad_pending_pool:
|
||
|
dm_kcopyd_client_destroy(s->kcopyd_client);
|
||
|
bad_kcopyd:
|
||
|
dm_exception_table_exit(&s->pending, pending_cache);
|
||
|
dm_exception_table_exit(&s->complete, exception_cache);
|
||
|
bad_hash_tables:
|
||
|
dm_exception_store_destroy(s->store);
|
||
|
bad_store:
|
||
|
dm_put_device(ti, s->cow);
|
||
|
bad_cow:
|
||
|
dm_put_device(ti, s->origin);
|
||
|
bad_origin:
|
||
|
bad_features:
|
||
|
kfree(s);
|
||
|
bad:
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
static void __free_exceptions(struct dm_snapshot *s)
|
||
|
{
|
||
|
dm_kcopyd_client_destroy(s->kcopyd_client);
|
||
|
s->kcopyd_client = NULL;
|
||
|
|
||
|
dm_exception_table_exit(&s->pending, pending_cache);
|
||
|
dm_exception_table_exit(&s->complete, exception_cache);
|
||
|
}
|
||
|
|
||
|
static void __handover_exceptions(struct dm_snapshot *snap_src,
|
||
|
struct dm_snapshot *snap_dest)
|
||
|
{
|
||
|
union {
|
||
|
struct dm_exception_table table_swap;
|
||
|
struct dm_exception_store *store_swap;
|
||
|
} u;
|
||
|
|
||
|
/*
|
||
|
* Swap all snapshot context information between the two instances.
|
||
|
*/
|
||
|
u.table_swap = snap_dest->complete;
|
||
|
snap_dest->complete = snap_src->complete;
|
||
|
snap_src->complete = u.table_swap;
|
||
|
|
||
|
u.store_swap = snap_dest->store;
|
||
|
snap_dest->store = snap_src->store;
|
||
|
snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
|
||
|
snap_src->store = u.store_swap;
|
||
|
|
||
|
snap_dest->store->snap = snap_dest;
|
||
|
snap_src->store->snap = snap_src;
|
||
|
|
||
|
snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
|
||
|
snap_dest->valid = snap_src->valid;
|
||
|
snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
|
||
|
|
||
|
/*
|
||
|
* Set source invalid to ensure it receives no further I/O.
|
||
|
*/
|
||
|
snap_src->valid = 0;
|
||
|
}
|
||
|
|
||
|
static void snapshot_dtr(struct dm_target *ti)
|
||
|
{
|
||
|
#ifdef CONFIG_DM_DEBUG
|
||
|
int i;
|
||
|
#endif
|
||
|
struct dm_snapshot *s = ti->private;
|
||
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
|
||
|
|
||
|
down_read(&_origins_lock);
|
||
|
/* Check whether exception handover must be cancelled */
|
||
|
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
|
||
|
if (snap_src && snap_dest && (s == snap_src)) {
|
||
|
down_write(&snap_dest->lock);
|
||
|
snap_dest->valid = 0;
|
||
|
up_write(&snap_dest->lock);
|
||
|
DMERR("Cancelling snapshot handover.");
|
||
|
}
|
||
|
up_read(&_origins_lock);
|
||
|
|
||
|
if (dm_target_is_snapshot_merge(ti))
|
||
|
stop_merge(s);
|
||
|
|
||
|
/* Prevent further origin writes from using this snapshot. */
|
||
|
/* After this returns there can be no new kcopyd jobs. */
|
||
|
unregister_snapshot(s);
|
||
|
|
||
|
while (atomic_read(&s->pending_exceptions_count))
|
||
|
msleep(1);
|
||
|
/*
|
||
|
* Ensure instructions in mempool_exit aren't reordered
|
||
|
* before atomic_read.
|
||
|
*/
|
||
|
smp_mb();
|
||
|
|
||
|
#ifdef CONFIG_DM_DEBUG
|
||
|
for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
|
||
|
BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
|
||
|
#endif
|
||
|
|
||
|
__free_exceptions(s);
|
||
|
|
||
|
mempool_exit(&s->pending_pool);
|
||
|
|
||
|
dm_exception_store_destroy(s->store);
|
||
|
|
||
|
dm_put_device(ti, s->cow);
|
||
|
|
||
|
dm_put_device(ti, s->origin);
|
||
|
|
||
|
WARN_ON(s->in_progress);
|
||
|
|
||
|
kfree(s);
|
||
|
}
|
||
|
|
||
|
static void account_start_copy(struct dm_snapshot *s)
|
||
|
{
|
||
|
spin_lock(&s->in_progress_wait.lock);
|
||
|
s->in_progress++;
|
||
|
spin_unlock(&s->in_progress_wait.lock);
|
||
|
}
|
||
|
|
||
|
static void account_end_copy(struct dm_snapshot *s)
|
||
|
{
|
||
|
spin_lock(&s->in_progress_wait.lock);
|
||
|
BUG_ON(!s->in_progress);
|
||
|
s->in_progress--;
|
||
|
if (likely(s->in_progress <= cow_threshold) &&
|
||
|
unlikely(waitqueue_active(&s->in_progress_wait)))
|
||
|
wake_up_locked(&s->in_progress_wait);
|
||
|
spin_unlock(&s->in_progress_wait.lock);
|
||
|
}
|
||
|
|
||
|
static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins)
|
||
|
{
|
||
|
if (unlikely(s->in_progress > cow_threshold)) {
|
||
|
spin_lock(&s->in_progress_wait.lock);
|
||
|
if (likely(s->in_progress > cow_threshold)) {
|
||
|
/*
|
||
|
* NOTE: this throttle doesn't account for whether
|
||
|
* the caller is servicing an IO that will trigger a COW
|
||
|
* so excess throttling may result for chunks not required
|
||
|
* to be COW'd. But if cow_threshold was reached, extra
|
||
|
* throttling is unlikely to negatively impact performance.
|
||
|
*/
|
||
|
DECLARE_WAITQUEUE(wait, current);
|
||
|
__add_wait_queue(&s->in_progress_wait, &wait);
|
||
|
__set_current_state(TASK_UNINTERRUPTIBLE);
|
||
|
spin_unlock(&s->in_progress_wait.lock);
|
||
|
if (unlock_origins)
|
||
|
up_read(&_origins_lock);
|
||
|
io_schedule();
|
||
|
remove_wait_queue(&s->in_progress_wait, &wait);
|
||
|
return false;
|
||
|
}
|
||
|
spin_unlock(&s->in_progress_wait.lock);
|
||
|
}
|
||
|
return true;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Flush a list of buffers.
|
||
|
*/
|
||
|
static void flush_bios(struct bio *bio)
|
||
|
{
|
||
|
struct bio *n;
|
||
|
|
||
|
while (bio) {
|
||
|
n = bio->bi_next;
|
||
|
bio->bi_next = NULL;
|
||
|
submit_bio_noacct(bio);
|
||
|
bio = n;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit);
|
||
|
|
||
|
/*
|
||
|
* Flush a list of buffers.
|
||
|
*/
|
||
|
static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
|
||
|
{
|
||
|
struct bio *n;
|
||
|
int r;
|
||
|
|
||
|
while (bio) {
|
||
|
n = bio->bi_next;
|
||
|
bio->bi_next = NULL;
|
||
|
r = do_origin(s->origin, bio, false);
|
||
|
if (r == DM_MAPIO_REMAPPED)
|
||
|
submit_bio_noacct(bio);
|
||
|
bio = n;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Error a list of buffers.
|
||
|
*/
|
||
|
static void error_bios(struct bio *bio)
|
||
|
{
|
||
|
struct bio *n;
|
||
|
|
||
|
while (bio) {
|
||
|
n = bio->bi_next;
|
||
|
bio->bi_next = NULL;
|
||
|
bio_io_error(bio);
|
||
|
bio = n;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
static void __invalidate_snapshot(struct dm_snapshot *s, int err)
|
||
|
{
|
||
|
if (!s->valid)
|
||
|
return;
|
||
|
|
||
|
if (err == -EIO)
|
||
|
DMERR("Invalidating snapshot: Error reading/writing.");
|
||
|
else if (err == -ENOMEM)
|
||
|
DMERR("Invalidating snapshot: Unable to allocate exception.");
|
||
|
|
||
|
if (s->store->type->drop_snapshot)
|
||
|
s->store->type->drop_snapshot(s->store);
|
||
|
|
||
|
s->valid = 0;
|
||
|
|
||
|
dm_table_event(s->ti->table);
|
||
|
}
|
||
|
|
||
|
static void invalidate_snapshot(struct dm_snapshot *s, int err)
|
||
|
{
|
||
|
down_write(&s->lock);
|
||
|
__invalidate_snapshot(s, err);
|
||
|
up_write(&s->lock);
|
||
|
}
|
||
|
|
||
|
static void pending_complete(void *context, int success)
|
||
|
{
|
||
|
struct dm_snap_pending_exception *pe = context;
|
||
|
struct dm_exception *e;
|
||
|
struct dm_snapshot *s = pe->snap;
|
||
|
struct bio *origin_bios = NULL;
|
||
|
struct bio *snapshot_bios = NULL;
|
||
|
struct bio *full_bio = NULL;
|
||
|
struct dm_exception_table_lock lock;
|
||
|
int error = 0;
|
||
|
|
||
|
dm_exception_table_lock_init(s, pe->e.old_chunk, &lock);
|
||
|
|
||
|
if (!success) {
|
||
|
/* Read/write error - snapshot is unusable */
|
||
|
invalidate_snapshot(s, -EIO);
|
||
|
error = 1;
|
||
|
|
||
|
dm_exception_table_lock(&lock);
|
||
|
goto out;
|
||
|
}
|
||
|
|
||
|
e = alloc_completed_exception(GFP_NOIO);
|
||
|
if (!e) {
|
||
|
invalidate_snapshot(s, -ENOMEM);
|
||
|
error = 1;
|
||
|
|
||
|
dm_exception_table_lock(&lock);
|
||
|
goto out;
|
||
|
}
|
||
|
*e = pe->e;
|
||
|
|
||
|
down_read(&s->lock);
|
||
|
dm_exception_table_lock(&lock);
|
||
|
if (!s->valid) {
|
||
|
up_read(&s->lock);
|
||
|
free_completed_exception(e);
|
||
|
error = 1;
|
||
|
|
||
|
goto out;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Add a proper exception. After inserting the completed exception all
|
||
|
* subsequent snapshot reads to this chunk will be redirected to the
|
||
|
* COW device. This ensures that we do not starve. Moreover, as long
|
||
|
* as the pending exception exists, neither origin writes nor snapshot
|
||
|
* merging can overwrite the chunk in origin.
|
||
|
*/
|
||
|
dm_insert_exception(&s->complete, e);
|
||
|
up_read(&s->lock);
|
||
|
|
||
|
/* Wait for conflicting reads to drain */
|
||
|
if (__chunk_is_tracked(s, pe->e.old_chunk)) {
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
__check_for_conflicting_io(s, pe->e.old_chunk);
|
||
|
dm_exception_table_lock(&lock);
|
||
|
}
|
||
|
|
||
|
out:
|
||
|
/* Remove the in-flight exception from the list */
|
||
|
dm_remove_exception(&pe->e);
|
||
|
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
|
||
|
snapshot_bios = bio_list_get(&pe->snapshot_bios);
|
||
|
origin_bios = bio_list_get(&pe->origin_bios);
|
||
|
full_bio = pe->full_bio;
|
||
|
if (full_bio)
|
||
|
full_bio->bi_end_io = pe->full_bio_end_io;
|
||
|
increment_pending_exceptions_done_count();
|
||
|
|
||
|
/* Submit any pending write bios */
|
||
|
if (error) {
|
||
|
if (full_bio)
|
||
|
bio_io_error(full_bio);
|
||
|
error_bios(snapshot_bios);
|
||
|
} else {
|
||
|
if (full_bio)
|
||
|
bio_endio(full_bio);
|
||
|
flush_bios(snapshot_bios);
|
||
|
}
|
||
|
|
||
|
retry_origin_bios(s, origin_bios);
|
||
|
|
||
|
free_pending_exception(pe);
|
||
|
}
|
||
|
|
||
|
static void complete_exception(struct dm_snap_pending_exception *pe)
|
||
|
{
|
||
|
struct dm_snapshot *s = pe->snap;
|
||
|
|
||
|
/* Update the metadata if we are persistent */
|
||
|
s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
|
||
|
pending_complete, pe);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Called when the copy I/O has finished. kcopyd actually runs
|
||
|
* this code so don't block.
|
||
|
*/
|
||
|
static void copy_callback(int read_err, unsigned long write_err, void *context)
|
||
|
{
|
||
|
struct dm_snap_pending_exception *pe = context;
|
||
|
struct dm_snapshot *s = pe->snap;
|
||
|
|
||
|
pe->copy_error = read_err || write_err;
|
||
|
|
||
|
if (pe->exception_sequence == s->exception_complete_sequence) {
|
||
|
struct rb_node *next;
|
||
|
|
||
|
s->exception_complete_sequence++;
|
||
|
complete_exception(pe);
|
||
|
|
||
|
next = rb_first(&s->out_of_order_tree);
|
||
|
while (next) {
|
||
|
pe = rb_entry(next, struct dm_snap_pending_exception,
|
||
|
out_of_order_node);
|
||
|
if (pe->exception_sequence != s->exception_complete_sequence)
|
||
|
break;
|
||
|
next = rb_next(next);
|
||
|
s->exception_complete_sequence++;
|
||
|
rb_erase(&pe->out_of_order_node, &s->out_of_order_tree);
|
||
|
complete_exception(pe);
|
||
|
cond_resched();
|
||
|
}
|
||
|
} else {
|
||
|
struct rb_node *parent = NULL;
|
||
|
struct rb_node **p = &s->out_of_order_tree.rb_node;
|
||
|
struct dm_snap_pending_exception *pe2;
|
||
|
|
||
|
while (*p) {
|
||
|
pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node);
|
||
|
parent = *p;
|
||
|
|
||
|
BUG_ON(pe->exception_sequence == pe2->exception_sequence);
|
||
|
if (pe->exception_sequence < pe2->exception_sequence)
|
||
|
p = &((*p)->rb_left);
|
||
|
else
|
||
|
p = &((*p)->rb_right);
|
||
|
}
|
||
|
|
||
|
rb_link_node(&pe->out_of_order_node, parent, p);
|
||
|
rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);
|
||
|
}
|
||
|
account_end_copy(s);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Dispatches the copy operation to kcopyd.
|
||
|
*/
|
||
|
static void start_copy(struct dm_snap_pending_exception *pe)
|
||
|
{
|
||
|
struct dm_snapshot *s = pe->snap;
|
||
|
struct dm_io_region src, dest;
|
||
|
struct block_device *bdev = s->origin->bdev;
|
||
|
sector_t dev_size;
|
||
|
|
||
|
dev_size = get_dev_size(bdev);
|
||
|
|
||
|
src.bdev = bdev;
|
||
|
src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
|
||
|
src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
|
||
|
|
||
|
dest.bdev = s->cow->bdev;
|
||
|
dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
|
||
|
dest.count = src.count;
|
||
|
|
||
|
/* Hand over to kcopyd */
|
||
|
account_start_copy(s);
|
||
|
dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
|
||
|
}
|
||
|
|
||
|
static void full_bio_end_io(struct bio *bio)
|
||
|
{
|
||
|
void *callback_data = bio->bi_private;
|
||
|
|
||
|
dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0);
|
||
|
}
|
||
|
|
||
|
static void start_full_bio(struct dm_snap_pending_exception *pe,
|
||
|
struct bio *bio)
|
||
|
{
|
||
|
struct dm_snapshot *s = pe->snap;
|
||
|
void *callback_data;
|
||
|
|
||
|
pe->full_bio = bio;
|
||
|
pe->full_bio_end_io = bio->bi_end_io;
|
||
|
|
||
|
account_start_copy(s);
|
||
|
callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
|
||
|
copy_callback, pe);
|
||
|
|
||
|
bio->bi_end_io = full_bio_end_io;
|
||
|
bio->bi_private = callback_data;
|
||
|
|
||
|
submit_bio_noacct(bio);
|
||
|
}
|
||
|
|
||
|
static struct dm_snap_pending_exception *
|
||
|
__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
|
||
|
{
|
||
|
struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
|
||
|
|
||
|
if (!e)
|
||
|
return NULL;
|
||
|
|
||
|
return container_of(e, struct dm_snap_pending_exception, e);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Inserts a pending exception into the pending table.
|
||
|
*
|
||
|
* NOTE: a write lock must be held on the chunk's pending exception table slot
|
||
|
* before calling this.
|
||
|
*/
|
||
|
static struct dm_snap_pending_exception *
|
||
|
__insert_pending_exception(struct dm_snapshot *s,
|
||
|
struct dm_snap_pending_exception *pe, chunk_t chunk)
|
||
|
{
|
||
|
pe->e.old_chunk = chunk;
|
||
|
bio_list_init(&pe->origin_bios);
|
||
|
bio_list_init(&pe->snapshot_bios);
|
||
|
pe->started = 0;
|
||
|
pe->full_bio = NULL;
|
||
|
|
||
|
spin_lock(&s->pe_allocation_lock);
|
||
|
if (s->store->type->prepare_exception(s->store, &pe->e)) {
|
||
|
spin_unlock(&s->pe_allocation_lock);
|
||
|
free_pending_exception(pe);
|
||
|
return NULL;
|
||
|
}
|
||
|
|
||
|
pe->exception_sequence = s->exception_start_sequence++;
|
||
|
spin_unlock(&s->pe_allocation_lock);
|
||
|
|
||
|
dm_insert_exception(&s->pending, &pe->e);
|
||
|
|
||
|
return pe;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Looks to see if this snapshot already has a pending exception
|
||
|
* for this chunk, otherwise it allocates a new one and inserts
|
||
|
* it into the pending table.
|
||
|
*
|
||
|
* NOTE: a write lock must be held on the chunk's pending exception table slot
|
||
|
* before calling this.
|
||
|
*/
|
||
|
static struct dm_snap_pending_exception *
|
||
|
__find_pending_exception(struct dm_snapshot *s,
|
||
|
struct dm_snap_pending_exception *pe, chunk_t chunk)
|
||
|
{
|
||
|
struct dm_snap_pending_exception *pe2;
|
||
|
|
||
|
pe2 = __lookup_pending_exception(s, chunk);
|
||
|
if (pe2) {
|
||
|
free_pending_exception(pe);
|
||
|
return pe2;
|
||
|
}
|
||
|
|
||
|
return __insert_pending_exception(s, pe, chunk);
|
||
|
}
|
||
|
|
||
|
static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
|
||
|
struct bio *bio, chunk_t chunk)
|
||
|
{
|
||
|
bio_set_dev(bio, s->cow->bdev);
|
||
|
bio->bi_iter.bi_sector =
|
||
|
chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) +
|
||
|
(chunk - e->old_chunk)) +
|
||
|
(bio->bi_iter.bi_sector & s->store->chunk_mask);
|
||
|
}
|
||
|
|
||
|
static void zero_callback(int read_err, unsigned long write_err, void *context)
|
||
|
{
|
||
|
struct bio *bio = context;
|
||
|
struct dm_snapshot *s = bio->bi_private;
|
||
|
|
||
|
account_end_copy(s);
|
||
|
bio->bi_status = write_err ? BLK_STS_IOERR : 0;
|
||
|
bio_endio(bio);
|
||
|
}
|
||
|
|
||
|
static void zero_exception(struct dm_snapshot *s, struct dm_exception *e,
|
||
|
struct bio *bio, chunk_t chunk)
|
||
|
{
|
||
|
struct dm_io_region dest;
|
||
|
|
||
|
dest.bdev = s->cow->bdev;
|
||
|
dest.sector = bio->bi_iter.bi_sector;
|
||
|
dest.count = s->store->chunk_size;
|
||
|
|
||
|
account_start_copy(s);
|
||
|
WARN_ON_ONCE(bio->bi_private);
|
||
|
bio->bi_private = s;
|
||
|
dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);
|
||
|
}
|
||
|
|
||
|
static bool io_overlaps_chunk(struct dm_snapshot *s, struct bio *bio)
|
||
|
{
|
||
|
return bio->bi_iter.bi_size ==
|
||
|
(s->store->chunk_size << SECTOR_SHIFT);
|
||
|
}
|
||
|
|
||
|
static int snapshot_map(struct dm_target *ti, struct bio *bio)
|
||
|
{
|
||
|
struct dm_exception *e;
|
||
|
struct dm_snapshot *s = ti->private;
|
||
|
int r = DM_MAPIO_REMAPPED;
|
||
|
chunk_t chunk;
|
||
|
struct dm_snap_pending_exception *pe = NULL;
|
||
|
struct dm_exception_table_lock lock;
|
||
|
|
||
|
init_tracked_chunk(bio);
|
||
|
|
||
|
if (bio->bi_opf & REQ_PREFLUSH) {
|
||
|
bio_set_dev(bio, s->cow->bdev);
|
||
|
return DM_MAPIO_REMAPPED;
|
||
|
}
|
||
|
|
||
|
chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
|
||
|
dm_exception_table_lock_init(s, chunk, &lock);
|
||
|
|
||
|
/* Full snapshots are not usable */
|
||
|
/* To get here the table must be live so s->active is always set. */
|
||
|
if (!s->valid)
|
||
|
return DM_MAPIO_KILL;
|
||
|
|
||
|
if (bio_data_dir(bio) == WRITE) {
|
||
|
while (unlikely(!wait_for_in_progress(s, false)))
|
||
|
; /* wait_for_in_progress() has slept */
|
||
|
}
|
||
|
|
||
|
down_read(&s->lock);
|
||
|
dm_exception_table_lock(&lock);
|
||
|
|
||
|
if (!s->valid || (unlikely(s->snapshot_overflowed) &&
|
||
|
bio_data_dir(bio) == WRITE)) {
|
||
|
r = DM_MAPIO_KILL;
|
||
|
goto out_unlock;
|
||
|
}
|
||
|
|
||
|
if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
|
||
|
if (s->discard_passdown_origin && dm_bio_get_target_bio_nr(bio)) {
|
||
|
/*
|
||
|
* passdown discard to origin (without triggering
|
||
|
* snapshot exceptions via do_origin; doing so would
|
||
|
* defeat the goal of freeing space in origin that is
|
||
|
* implied by the "discard_passdown_origin" feature)
|
||
|
*/
|
||
|
bio_set_dev(bio, s->origin->bdev);
|
||
|
track_chunk(s, bio, chunk);
|
||
|
goto out_unlock;
|
||
|
}
|
||
|
/* discard to snapshot (target_bio_nr == 0) zeroes exceptions */
|
||
|
}
|
||
|
|
||
|
/* If the block is already remapped - use that, else remap it */
|
||
|
e = dm_lookup_exception(&s->complete, chunk);
|
||
|
if (e) {
|
||
|
remap_exception(s, e, bio, chunk);
|
||
|
if (unlikely(bio_op(bio) == REQ_OP_DISCARD) &&
|
||
|
io_overlaps_chunk(s, bio)) {
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
up_read(&s->lock);
|
||
|
zero_exception(s, e, bio, chunk);
|
||
|
r = DM_MAPIO_SUBMITTED; /* discard is not issued */
|
||
|
goto out;
|
||
|
}
|
||
|
goto out_unlock;
|
||
|
}
|
||
|
|
||
|
if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
|
||
|
/*
|
||
|
* If no exception exists, complete discard immediately
|
||
|
* otherwise it'll trigger copy-out.
|
||
|
*/
|
||
|
bio_endio(bio);
|
||
|
r = DM_MAPIO_SUBMITTED;
|
||
|
goto out_unlock;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Write to snapshot - higher level takes care of RW/RO
|
||
|
* flags so we should only get this if we are
|
||
|
* writable.
|
||
|
*/
|
||
|
if (bio_data_dir(bio) == WRITE) {
|
||
|
pe = __lookup_pending_exception(s, chunk);
|
||
|
if (!pe) {
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
pe = alloc_pending_exception(s);
|
||
|
dm_exception_table_lock(&lock);
|
||
|
|
||
|
e = dm_lookup_exception(&s->complete, chunk);
|
||
|
if (e) {
|
||
|
free_pending_exception(pe);
|
||
|
remap_exception(s, e, bio, chunk);
|
||
|
goto out_unlock;
|
||
|
}
|
||
|
|
||
|
pe = __find_pending_exception(s, pe, chunk);
|
||
|
if (!pe) {
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
up_read(&s->lock);
|
||
|
|
||
|
down_write(&s->lock);
|
||
|
|
||
|
if (s->store->userspace_supports_overflow) {
|
||
|
if (s->valid && !s->snapshot_overflowed) {
|
||
|
s->snapshot_overflowed = 1;
|
||
|
DMERR("Snapshot overflowed: Unable to allocate exception.");
|
||
|
}
|
||
|
} else
|
||
|
__invalidate_snapshot(s, -ENOMEM);
|
||
|
up_write(&s->lock);
|
||
|
|
||
|
r = DM_MAPIO_KILL;
|
||
|
goto out;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
remap_exception(s, &pe->e, bio, chunk);
|
||
|
|
||
|
r = DM_MAPIO_SUBMITTED;
|
||
|
|
||
|
if (!pe->started && io_overlaps_chunk(s, bio)) {
|
||
|
pe->started = 1;
|
||
|
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
up_read(&s->lock);
|
||
|
|
||
|
start_full_bio(pe, bio);
|
||
|
goto out;
|
||
|
}
|
||
|
|
||
|
bio_list_add(&pe->snapshot_bios, bio);
|
||
|
|
||
|
if (!pe->started) {
|
||
|
/* this is protected by the exception table lock */
|
||
|
pe->started = 1;
|
||
|
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
up_read(&s->lock);
|
||
|
|
||
|
start_copy(pe);
|
||
|
goto out;
|
||
|
}
|
||
|
} else {
|
||
|
bio_set_dev(bio, s->origin->bdev);
|
||
|
track_chunk(s, bio, chunk);
|
||
|
}
|
||
|
|
||
|
out_unlock:
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
up_read(&s->lock);
|
||
|
out:
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* A snapshot-merge target behaves like a combination of a snapshot
|
||
|
* target and a snapshot-origin target. It only generates new
|
||
|
* exceptions in other snapshots and not in the one that is being
|
||
|
* merged.
|
||
|
*
|
||
|
* For each chunk, if there is an existing exception, it is used to
|
||
|
* redirect I/O to the cow device. Otherwise I/O is sent to the origin,
|
||
|
* which in turn might generate exceptions in other snapshots.
|
||
|
* If merging is currently taking place on the chunk in question, the
|
||
|
* I/O is deferred by adding it to s->bios_queued_during_merge.
|
||
|
*/
|
||
|
static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
|
||
|
{
|
||
|
struct dm_exception *e;
|
||
|
struct dm_snapshot *s = ti->private;
|
||
|
int r = DM_MAPIO_REMAPPED;
|
||
|
chunk_t chunk;
|
||
|
|
||
|
init_tracked_chunk(bio);
|
||
|
|
||
|
if (bio->bi_opf & REQ_PREFLUSH) {
|
||
|
if (!dm_bio_get_target_bio_nr(bio))
|
||
|
bio_set_dev(bio, s->origin->bdev);
|
||
|
else
|
||
|
bio_set_dev(bio, s->cow->bdev);
|
||
|
return DM_MAPIO_REMAPPED;
|
||
|
}
|
||
|
|
||
|
if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
|
||
|
/* Once merging, discards no longer effect change */
|
||
|
bio_endio(bio);
|
||
|
return DM_MAPIO_SUBMITTED;
|
||
|
}
|
||
|
|
||
|
chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
|
||
|
|
||
|
down_write(&s->lock);
|
||
|
|
||
|
/* Full merging snapshots are redirected to the origin */
|
||
|
if (!s->valid)
|
||
|
goto redirect_to_origin;
|
||
|
|
||
|
/* If the block is already remapped - use that */
|
||
|
e = dm_lookup_exception(&s->complete, chunk);
|
||
|
if (e) {
|
||
|
/* Queue writes overlapping with chunks being merged */
|
||
|
if (bio_data_dir(bio) == WRITE &&
|
||
|
chunk >= s->first_merging_chunk &&
|
||
|
chunk < (s->first_merging_chunk +
|
||
|
s->num_merging_chunks)) {
|
||
|
bio_set_dev(bio, s->origin->bdev);
|
||
|
bio_list_add(&s->bios_queued_during_merge, bio);
|
||
|
r = DM_MAPIO_SUBMITTED;
|
||
|
goto out_unlock;
|
||
|
}
|
||
|
|
||
|
remap_exception(s, e, bio, chunk);
|
||
|
|
||
|
if (bio_data_dir(bio) == WRITE)
|
||
|
track_chunk(s, bio, chunk);
|
||
|
goto out_unlock;
|
||
|
}
|
||
|
|
||
|
redirect_to_origin:
|
||
|
bio_set_dev(bio, s->origin->bdev);
|
||
|
|
||
|
if (bio_data_dir(bio) == WRITE) {
|
||
|
up_write(&s->lock);
|
||
|
return do_origin(s->origin, bio, false);
|
||
|
}
|
||
|
|
||
|
out_unlock:
|
||
|
up_write(&s->lock);
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
|
||
|
blk_status_t *error)
|
||
|
{
|
||
|
struct dm_snapshot *s = ti->private;
|
||
|
|
||
|
if (is_bio_tracked(bio))
|
||
|
stop_tracking_chunk(s, bio);
|
||
|
|
||
|
return DM_ENDIO_DONE;
|
||
|
}
|
||
|
|
||
|
static void snapshot_merge_presuspend(struct dm_target *ti)
|
||
|
{
|
||
|
struct dm_snapshot *s = ti->private;
|
||
|
|
||
|
stop_merge(s);
|
||
|
}
|
||
|
|
||
|
static int snapshot_preresume(struct dm_target *ti)
|
||
|
{
|
||
|
int r = 0;
|
||
|
struct dm_snapshot *s = ti->private;
|
||
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
|
||
|
|
||
|
down_read(&_origins_lock);
|
||
|
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
|
||
|
if (snap_src && snap_dest) {
|
||
|
down_read(&snap_src->lock);
|
||
|
if (s == snap_src) {
|
||
|
DMERR("Unable to resume snapshot source until handover completes.");
|
||
|
r = -EINVAL;
|
||
|
} else if (!dm_suspended(snap_src->ti)) {
|
||
|
DMERR("Unable to perform snapshot handover until source is suspended.");
|
||
|
r = -EINVAL;
|
||
|
}
|
||
|
up_read(&snap_src->lock);
|
||
|
}
|
||
|
up_read(&_origins_lock);
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
static void snapshot_resume(struct dm_target *ti)
|
||
|
{
|
||
|
struct dm_snapshot *s = ti->private;
|
||
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;
|
||
|
struct dm_origin *o;
|
||
|
struct mapped_device *origin_md = NULL;
|
||
|
bool must_restart_merging = false;
|
||
|
|
||
|
down_read(&_origins_lock);
|
||
|
|
||
|
o = __lookup_dm_origin(s->origin->bdev);
|
||
|
if (o)
|
||
|
origin_md = dm_table_get_md(o->ti->table);
|
||
|
if (!origin_md) {
|
||
|
(void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);
|
||
|
if (snap_merging)
|
||
|
origin_md = dm_table_get_md(snap_merging->ti->table);
|
||
|
}
|
||
|
if (origin_md == dm_table_get_md(ti->table))
|
||
|
origin_md = NULL;
|
||
|
if (origin_md) {
|
||
|
if (dm_hold(origin_md))
|
||
|
origin_md = NULL;
|
||
|
}
|
||
|
|
||
|
up_read(&_origins_lock);
|
||
|
|
||
|
if (origin_md) {
|
||
|
dm_internal_suspend_fast(origin_md);
|
||
|
if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {
|
||
|
must_restart_merging = true;
|
||
|
stop_merge(snap_merging);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
down_read(&_origins_lock);
|
||
|
|
||
|
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
|
||
|
if (snap_src && snap_dest) {
|
||
|
down_write(&snap_src->lock);
|
||
|
down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
|
||
|
__handover_exceptions(snap_src, snap_dest);
|
||
|
up_write(&snap_dest->lock);
|
||
|
up_write(&snap_src->lock);
|
||
|
}
|
||
|
|
||
|
up_read(&_origins_lock);
|
||
|
|
||
|
if (origin_md) {
|
||
|
if (must_restart_merging)
|
||
|
start_merge(snap_merging);
|
||
|
dm_internal_resume_fast(origin_md);
|
||
|
dm_put(origin_md);
|
||
|
}
|
||
|
|
||
|
/* Now we have correct chunk size, reregister */
|
||
|
reregister_snapshot(s);
|
||
|
|
||
|
down_write(&s->lock);
|
||
|
s->active = 1;
|
||
|
up_write(&s->lock);
|
||
|
}
|
||
|
|
||
|
static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
|
||
|
{
|
||
|
uint32_t min_chunksize;
|
||
|
|
||
|
down_read(&_origins_lock);
|
||
|
min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
|
||
|
up_read(&_origins_lock);
|
||
|
|
||
|
return min_chunksize;
|
||
|
}
|
||
|
|
||
|
static void snapshot_merge_resume(struct dm_target *ti)
|
||
|
{
|
||
|
struct dm_snapshot *s = ti->private;
|
||
|
|
||
|
/*
|
||
|
* Handover exceptions from existing snapshot.
|
||
|
*/
|
||
|
snapshot_resume(ti);
|
||
|
|
||
|
/*
|
||
|
* snapshot-merge acts as an origin, so set ti->max_io_len
|
||
|
*/
|
||
|
ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
|
||
|
|
||
|
start_merge(s);
|
||
|
}
|
||
|
|
||
|
static void snapshot_status(struct dm_target *ti, status_type_t type,
|
||
|
unsigned int status_flags, char *result, unsigned int maxlen)
|
||
|
{
|
||
|
unsigned int sz = 0;
|
||
|
struct dm_snapshot *snap = ti->private;
|
||
|
unsigned int num_features;
|
||
|
|
||
|
switch (type) {
|
||
|
case STATUSTYPE_INFO:
|
||
|
|
||
|
down_write(&snap->lock);
|
||
|
|
||
|
if (!snap->valid)
|
||
|
DMEMIT("Invalid");
|
||
|
else if (snap->merge_failed)
|
||
|
DMEMIT("Merge failed");
|
||
|
else if (snap->snapshot_overflowed)
|
||
|
DMEMIT("Overflow");
|
||
|
else {
|
||
|
if (snap->store->type->usage) {
|
||
|
sector_t total_sectors, sectors_allocated,
|
||
|
metadata_sectors;
|
||
|
snap->store->type->usage(snap->store,
|
||
|
&total_sectors,
|
||
|
§ors_allocated,
|
||
|
&metadata_sectors);
|
||
|
DMEMIT("%llu/%llu %llu",
|
||
|
(unsigned long long)sectors_allocated,
|
||
|
(unsigned long long)total_sectors,
|
||
|
(unsigned long long)metadata_sectors);
|
||
|
}
|
||
|
else
|
||
|
DMEMIT("Unknown");
|
||
|
}
|
||
|
|
||
|
up_write(&snap->lock);
|
||
|
|
||
|
break;
|
||
|
|
||
|
case STATUSTYPE_TABLE:
|
||
|
/*
|
||
|
* kdevname returns a static pointer so we need
|
||
|
* to make private copies if the output is to
|
||
|
* make sense.
|
||
|
*/
|
||
|
DMEMIT("%s %s", snap->origin->name, snap->cow->name);
|
||
|
sz += snap->store->type->status(snap->store, type, result + sz,
|
||
|
maxlen - sz);
|
||
|
num_features = snap->discard_zeroes_cow + snap->discard_passdown_origin;
|
||
|
if (num_features) {
|
||
|
DMEMIT(" %u", num_features);
|
||
|
if (snap->discard_zeroes_cow)
|
||
|
DMEMIT(" discard_zeroes_cow");
|
||
|
if (snap->discard_passdown_origin)
|
||
|
DMEMIT(" discard_passdown_origin");
|
||
|
}
|
||
|
break;
|
||
|
|
||
|
case STATUSTYPE_IMA:
|
||
|
DMEMIT_TARGET_NAME_VERSION(ti->type);
|
||
|
DMEMIT(",snap_origin_name=%s", snap->origin->name);
|
||
|
DMEMIT(",snap_cow_name=%s", snap->cow->name);
|
||
|
DMEMIT(",snap_valid=%c", snap->valid ? 'y' : 'n');
|
||
|
DMEMIT(",snap_merge_failed=%c", snap->merge_failed ? 'y' : 'n');
|
||
|
DMEMIT(",snapshot_overflowed=%c", snap->snapshot_overflowed ? 'y' : 'n');
|
||
|
DMEMIT(";");
|
||
|
break;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
static int snapshot_iterate_devices(struct dm_target *ti,
|
||
|
iterate_devices_callout_fn fn, void *data)
|
||
|
{
|
||
|
struct dm_snapshot *snap = ti->private;
|
||
|
int r;
|
||
|
|
||
|
r = fn(ti, snap->origin, 0, ti->len, data);
|
||
|
|
||
|
if (!r)
|
||
|
r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits)
|
||
|
{
|
||
|
struct dm_snapshot *snap = ti->private;
|
||
|
|
||
|
if (snap->discard_zeroes_cow) {
|
||
|
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
|
||
|
|
||
|
down_read(&_origins_lock);
|
||
|
|
||
|
(void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL);
|
||
|
if (snap_src && snap_dest)
|
||
|
snap = snap_src;
|
||
|
|
||
|
/* All discards are split on chunk_size boundary */
|
||
|
limits->discard_granularity = snap->store->chunk_size;
|
||
|
limits->max_discard_sectors = snap->store->chunk_size;
|
||
|
|
||
|
up_read(&_origins_lock);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
/*-----------------------------------------------------------------
|
||
|
* Origin methods
|
||
|
*---------------------------------------------------------------*/
|
||
|
|
||
|
/*
|
||
|
* If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
|
||
|
* supplied bio was ignored. The caller may submit it immediately.
|
||
|
* (No remapping actually occurs as the origin is always a direct linear
|
||
|
* map.)
|
||
|
*
|
||
|
* If further exceptions are required, DM_MAPIO_SUBMITTED is returned
|
||
|
* and any supplied bio is added to a list to be submitted once all
|
||
|
* the necessary exceptions exist.
|
||
|
*/
|
||
|
static int __origin_write(struct list_head *snapshots, sector_t sector,
|
||
|
struct bio *bio)
|
||
|
{
|
||
|
int r = DM_MAPIO_REMAPPED;
|
||
|
struct dm_snapshot *snap;
|
||
|
struct dm_exception *e;
|
||
|
struct dm_snap_pending_exception *pe, *pe2;
|
||
|
struct dm_snap_pending_exception *pe_to_start_now = NULL;
|
||
|
struct dm_snap_pending_exception *pe_to_start_last = NULL;
|
||
|
struct dm_exception_table_lock lock;
|
||
|
chunk_t chunk;
|
||
|
|
||
|
/* Do all the snapshots on this origin */
|
||
|
list_for_each_entry(snap, snapshots, list) {
|
||
|
/*
|
||
|
* Don't make new exceptions in a merging snapshot
|
||
|
* because it has effectively been deleted
|
||
|
*/
|
||
|
if (dm_target_is_snapshot_merge(snap->ti))
|
||
|
continue;
|
||
|
|
||
|
/* Nothing to do if writing beyond end of snapshot */
|
||
|
if (sector >= dm_table_get_size(snap->ti->table))
|
||
|
continue;
|
||
|
|
||
|
/*
|
||
|
* Remember, different snapshots can have
|
||
|
* different chunk sizes.
|
||
|
*/
|
||
|
chunk = sector_to_chunk(snap->store, sector);
|
||
|
dm_exception_table_lock_init(snap, chunk, &lock);
|
||
|
|
||
|
down_read(&snap->lock);
|
||
|
dm_exception_table_lock(&lock);
|
||
|
|
||
|
/* Only deal with valid and active snapshots */
|
||
|
if (!snap->valid || !snap->active)
|
||
|
goto next_snapshot;
|
||
|
|
||
|
pe = __lookup_pending_exception(snap, chunk);
|
||
|
if (!pe) {
|
||
|
/*
|
||
|
* Check exception table to see if block is already
|
||
|
* remapped in this snapshot and trigger an exception
|
||
|
* if not.
|
||
|
*/
|
||
|
e = dm_lookup_exception(&snap->complete, chunk);
|
||
|
if (e)
|
||
|
goto next_snapshot;
|
||
|
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
pe = alloc_pending_exception(snap);
|
||
|
dm_exception_table_lock(&lock);
|
||
|
|
||
|
pe2 = __lookup_pending_exception(snap, chunk);
|
||
|
|
||
|
if (!pe2) {
|
||
|
e = dm_lookup_exception(&snap->complete, chunk);
|
||
|
if (e) {
|
||
|
free_pending_exception(pe);
|
||
|
goto next_snapshot;
|
||
|
}
|
||
|
|
||
|
pe = __insert_pending_exception(snap, pe, chunk);
|
||
|
if (!pe) {
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
up_read(&snap->lock);
|
||
|
|
||
|
invalidate_snapshot(snap, -ENOMEM);
|
||
|
continue;
|
||
|
}
|
||
|
} else {
|
||
|
free_pending_exception(pe);
|
||
|
pe = pe2;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
r = DM_MAPIO_SUBMITTED;
|
||
|
|
||
|
/*
|
||
|
* If an origin bio was supplied, queue it to wait for the
|
||
|
* completion of this exception, and start this one last,
|
||
|
* at the end of the function.
|
||
|
*/
|
||
|
if (bio) {
|
||
|
bio_list_add(&pe->origin_bios, bio);
|
||
|
bio = NULL;
|
||
|
|
||
|
if (!pe->started) {
|
||
|
pe->started = 1;
|
||
|
pe_to_start_last = pe;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
if (!pe->started) {
|
||
|
pe->started = 1;
|
||
|
pe_to_start_now = pe;
|
||
|
}
|
||
|
|
||
|
next_snapshot:
|
||
|
dm_exception_table_unlock(&lock);
|
||
|
up_read(&snap->lock);
|
||
|
|
||
|
if (pe_to_start_now) {
|
||
|
start_copy(pe_to_start_now);
|
||
|
pe_to_start_now = NULL;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Submit the exception against which the bio is queued last,
|
||
|
* to give the other exceptions a head start.
|
||
|
*/
|
||
|
if (pe_to_start_last)
|
||
|
start_copy(pe_to_start_last);
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Called on a write from the origin driver.
|
||
|
*/
|
||
|
static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit)
|
||
|
{
|
||
|
struct origin *o;
|
||
|
int r = DM_MAPIO_REMAPPED;
|
||
|
|
||
|
again:
|
||
|
down_read(&_origins_lock);
|
||
|
o = __lookup_origin(origin->bdev);
|
||
|
if (o) {
|
||
|
if (limit) {
|
||
|
struct dm_snapshot *s;
|
||
|
list_for_each_entry(s, &o->snapshots, list)
|
||
|
if (unlikely(!wait_for_in_progress(s, true)))
|
||
|
goto again;
|
||
|
}
|
||
|
|
||
|
r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);
|
||
|
}
|
||
|
up_read(&_origins_lock);
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Trigger exceptions in all non-merging snapshots.
|
||
|
*
|
||
|
* The chunk size of the merging snapshot may be larger than the chunk
|
||
|
* size of some other snapshot so we may need to reallocate multiple
|
||
|
* chunks in other snapshots.
|
||
|
*
|
||
|
* We scan all the overlapping exceptions in the other snapshots.
|
||
|
* Returns 1 if anything was reallocated and must be waited for,
|
||
|
* otherwise returns 0.
|
||
|
*
|
||
|
* size must be a multiple of merging_snap's chunk_size.
|
||
|
*/
|
||
|
static int origin_write_extent(struct dm_snapshot *merging_snap,
|
||
|
sector_t sector, unsigned int size)
|
||
|
{
|
||
|
int must_wait = 0;
|
||
|
sector_t n;
|
||
|
struct origin *o;
|
||
|
|
||
|
/*
|
||
|
* The origin's __minimum_chunk_size() got stored in max_io_len
|
||
|
* by snapshot_merge_resume().
|
||
|
*/
|
||
|
down_read(&_origins_lock);
|
||
|
o = __lookup_origin(merging_snap->origin->bdev);
|
||
|
for (n = 0; n < size; n += merging_snap->ti->max_io_len)
|
||
|
if (__origin_write(&o->snapshots, sector + n, NULL) ==
|
||
|
DM_MAPIO_SUBMITTED)
|
||
|
must_wait = 1;
|
||
|
up_read(&_origins_lock);
|
||
|
|
||
|
return must_wait;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Origin: maps a linear range of a device, with hooks for snapshotting.
|
||
|
*/
|
||
|
|
||
|
/*
|
||
|
* Construct an origin mapping: <dev_path>
|
||
|
* The context for an origin is merely a 'struct dm_dev *'
|
||
|
* pointing to the real device.
|
||
|
*/
|
||
|
static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
|
||
|
{
|
||
|
int r;
|
||
|
struct dm_origin *o;
|
||
|
|
||
|
if (argc != 1) {
|
||
|
ti->error = "origin: incorrect number of arguments";
|
||
|
return -EINVAL;
|
||
|
}
|
||
|
|
||
|
o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL);
|
||
|
if (!o) {
|
||
|
ti->error = "Cannot allocate private origin structure";
|
||
|
r = -ENOMEM;
|
||
|
goto bad_alloc;
|
||
|
}
|
||
|
|
||
|
r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev);
|
||
|
if (r) {
|
||
|
ti->error = "Cannot get target device";
|
||
|
goto bad_open;
|
||
|
}
|
||
|
|
||
|
o->ti = ti;
|
||
|
ti->private = o;
|
||
|
ti->num_flush_bios = 1;
|
||
|
|
||
|
return 0;
|
||
|
|
||
|
bad_open:
|
||
|
kfree(o);
|
||
|
bad_alloc:
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
static void origin_dtr(struct dm_target *ti)
|
||
|
{
|
||
|
struct dm_origin *o = ti->private;
|
||
|
|
||
|
dm_put_device(ti, o->dev);
|
||
|
kfree(o);
|
||
|
}
|
||
|
|
||
|
static int origin_map(struct dm_target *ti, struct bio *bio)
|
||
|
{
|
||
|
struct dm_origin *o = ti->private;
|
||
|
unsigned int available_sectors;
|
||
|
|
||
|
bio_set_dev(bio, o->dev->bdev);
|
||
|
|
||
|
if (unlikely(bio->bi_opf & REQ_PREFLUSH))
|
||
|
return DM_MAPIO_REMAPPED;
|
||
|
|
||
|
if (bio_data_dir(bio) != WRITE)
|
||
|
return DM_MAPIO_REMAPPED;
|
||
|
|
||
|
available_sectors = o->split_boundary -
|
||
|
((unsigned int)bio->bi_iter.bi_sector & (o->split_boundary - 1));
|
||
|
|
||
|
if (bio_sectors(bio) > available_sectors)
|
||
|
dm_accept_partial_bio(bio, available_sectors);
|
||
|
|
||
|
/* Only tell snapshots if this is a write */
|
||
|
return do_origin(o->dev, bio, true);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* Set the target "max_io_len" field to the minimum of all the snapshots'
|
||
|
* chunk sizes.
|
||
|
*/
|
||
|
static void origin_resume(struct dm_target *ti)
|
||
|
{
|
||
|
struct dm_origin *o = ti->private;
|
||
|
|
||
|
o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev);
|
||
|
|
||
|
down_write(&_origins_lock);
|
||
|
__insert_dm_origin(o);
|
||
|
up_write(&_origins_lock);
|
||
|
}
|
||
|
|
||
|
static void origin_postsuspend(struct dm_target *ti)
|
||
|
{
|
||
|
struct dm_origin *o = ti->private;
|
||
|
|
||
|
down_write(&_origins_lock);
|
||
|
__remove_dm_origin(o);
|
||
|
up_write(&_origins_lock);
|
||
|
}
|
||
|
|
||
|
static void origin_status(struct dm_target *ti, status_type_t type,
|
||
|
unsigned int status_flags, char *result, unsigned int maxlen)
|
||
|
{
|
||
|
struct dm_origin *o = ti->private;
|
||
|
|
||
|
switch (type) {
|
||
|
case STATUSTYPE_INFO:
|
||
|
result[0] = '\0';
|
||
|
break;
|
||
|
|
||
|
case STATUSTYPE_TABLE:
|
||
|
snprintf(result, maxlen, "%s", o->dev->name);
|
||
|
break;
|
||
|
case STATUSTYPE_IMA:
|
||
|
result[0] = '\0';
|
||
|
break;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
static int origin_iterate_devices(struct dm_target *ti,
|
||
|
iterate_devices_callout_fn fn, void *data)
|
||
|
{
|
||
|
struct dm_origin *o = ti->private;
|
||
|
|
||
|
return fn(ti, o->dev, 0, ti->len, data);
|
||
|
}
|
||
|
|
||
|
static struct target_type origin_target = {
|
||
|
.name = "snapshot-origin",
|
||
|
.version = {1, 9, 0},
|
||
|
.module = THIS_MODULE,
|
||
|
.ctr = origin_ctr,
|
||
|
.dtr = origin_dtr,
|
||
|
.map = origin_map,
|
||
|
.resume = origin_resume,
|
||
|
.postsuspend = origin_postsuspend,
|
||
|
.status = origin_status,
|
||
|
.iterate_devices = origin_iterate_devices,
|
||
|
};
|
||
|
|
||
|
static struct target_type snapshot_target = {
|
||
|
.name = "snapshot",
|
||
|
.version = {1, 16, 0},
|
||
|
.module = THIS_MODULE,
|
||
|
.ctr = snapshot_ctr,
|
||
|
.dtr = snapshot_dtr,
|
||
|
.map = snapshot_map,
|
||
|
.end_io = snapshot_end_io,
|
||
|
.preresume = snapshot_preresume,
|
||
|
.resume = snapshot_resume,
|
||
|
.status = snapshot_status,
|
||
|
.iterate_devices = snapshot_iterate_devices,
|
||
|
.io_hints = snapshot_io_hints,
|
||
|
};
|
||
|
|
||
|
static struct target_type merge_target = {
|
||
|
.name = dm_snapshot_merge_target_name,
|
||
|
.version = {1, 5, 0},
|
||
|
.module = THIS_MODULE,
|
||
|
.ctr = snapshot_ctr,
|
||
|
.dtr = snapshot_dtr,
|
||
|
.map = snapshot_merge_map,
|
||
|
.end_io = snapshot_end_io,
|
||
|
.presuspend = snapshot_merge_presuspend,
|
||
|
.preresume = snapshot_preresume,
|
||
|
.resume = snapshot_merge_resume,
|
||
|
.status = snapshot_status,
|
||
|
.iterate_devices = snapshot_iterate_devices,
|
||
|
.io_hints = snapshot_io_hints,
|
||
|
};
|
||
|
|
||
|
static int __init dm_snapshot_init(void)
|
||
|
{
|
||
|
int r;
|
||
|
|
||
|
r = dm_exception_store_init();
|
||
|
if (r) {
|
||
|
DMERR("Failed to initialize exception stores");
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
r = init_origin_hash();
|
||
|
if (r) {
|
||
|
DMERR("init_origin_hash failed.");
|
||
|
goto bad_origin_hash;
|
||
|
}
|
||
|
|
||
|
exception_cache = KMEM_CACHE(dm_exception, 0);
|
||
|
if (!exception_cache) {
|
||
|
DMERR("Couldn't create exception cache.");
|
||
|
r = -ENOMEM;
|
||
|
goto bad_exception_cache;
|
||
|
}
|
||
|
|
||
|
pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
|
||
|
if (!pending_cache) {
|
||
|
DMERR("Couldn't create pending cache.");
|
||
|
r = -ENOMEM;
|
||
|
goto bad_pending_cache;
|
||
|
}
|
||
|
|
||
|
r = dm_register_target(&snapshot_target);
|
||
|
if (r < 0) {
|
||
|
DMERR("snapshot target register failed %d", r);
|
||
|
goto bad_register_snapshot_target;
|
||
|
}
|
||
|
|
||
|
r = dm_register_target(&origin_target);
|
||
|
if (r < 0) {
|
||
|
DMERR("Origin target register failed %d", r);
|
||
|
goto bad_register_origin_target;
|
||
|
}
|
||
|
|
||
|
r = dm_register_target(&merge_target);
|
||
|
if (r < 0) {
|
||
|
DMERR("Merge target register failed %d", r);
|
||
|
goto bad_register_merge_target;
|
||
|
}
|
||
|
|
||
|
return 0;
|
||
|
|
||
|
bad_register_merge_target:
|
||
|
dm_unregister_target(&origin_target);
|
||
|
bad_register_origin_target:
|
||
|
dm_unregister_target(&snapshot_target);
|
||
|
bad_register_snapshot_target:
|
||
|
kmem_cache_destroy(pending_cache);
|
||
|
bad_pending_cache:
|
||
|
kmem_cache_destroy(exception_cache);
|
||
|
bad_exception_cache:
|
||
|
exit_origin_hash();
|
||
|
bad_origin_hash:
|
||
|
dm_exception_store_exit();
|
||
|
|
||
|
return r;
|
||
|
}
|
||
|
|
||
|
static void __exit dm_snapshot_exit(void)
|
||
|
{
|
||
|
dm_unregister_target(&snapshot_target);
|
||
|
dm_unregister_target(&origin_target);
|
||
|
dm_unregister_target(&merge_target);
|
||
|
|
||
|
exit_origin_hash();
|
||
|
kmem_cache_destroy(pending_cache);
|
||
|
kmem_cache_destroy(exception_cache);
|
||
|
|
||
|
dm_exception_store_exit();
|
||
|
}
|
||
|
|
||
|
/* Module hooks */
|
||
|
module_init(dm_snapshot_init);
|
||
|
module_exit(dm_snapshot_exit);
|
||
|
|
||
|
MODULE_DESCRIPTION(DM_NAME " snapshot target");
|
||
|
MODULE_AUTHOR("Joe Thornber");
|
||
|
MODULE_LICENSE("GPL");
|
||
|
MODULE_ALIAS("dm-snapshot-origin");
|
||
|
MODULE_ALIAS("dm-snapshot-merge");
|