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9pfs changes:

Browse Source 
* Greg Kurz steps back as maintainer of 9pfs.
 
 * Make multidevs=remap default option (instead of multidevs=warn)
   and update documentation related to this option.
 
 * Improve tracing (i.e. usefulness of log output content).
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Merge tag 'pull-9p-20250207' of https://github.com/cschoenebeck/qemu into staging

9pfs changes:

* Greg Kurz steps back as maintainer of 9pfs.

* Make multidevs=remap default option (instead of multidevs=warn)
  and update documentation related to this option.

* Improve tracing (i.e. usefulness of log output content).

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# gpg: Signature made Fri 07 Feb 2025 04:53:05 EST
# gpg:                using RSA key 96D8D110CF7AF8084F88590134C2B58765A47395
# gpg:                issuer "qemu_oss@crudebyte.com"
# gpg: Good signature from "Christian Schoenebeck <qemu_oss@crudebyte.com>" [unknown]
# gpg: WARNING: The key's User ID is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: ECAB 1A45 4014 1413 BA38  4926 30DB 47C3 A012 D5F4
#      Subkey fingerprint: 96D8 D110 CF7A F808 4F88  5901 34C2 B587 65A4 7395

* tag 'pull-9p-20250207' of https://github.com/cschoenebeck/qemu:
  MAINTAINERS: Mark me as reviewer only for 9pfs
  9pfs: improve v9fs_open() tracing
  9pfs: make multidevs=remap default
  9pfs: improve v9fs_walk() tracing

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2025-02-07 09:26:59 -05:00
commit 0a841b0b64
8 changed files with 129 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
MAINTAINERS
View File

@ -2254,8 +2254,8 @@ F: include/system/balloon.h
F: tests/qtest/virtio-balloon-test.c
virtio-9p
M: Greg Kurz <groug@kaod.org>
M: Christian Schoenebeck <qemu_oss@crudebyte.com>
R: Greg Kurz <groug@kaod.org>
S: Maintained
W: https://wiki.qemu.org/Documentation/9p
F: hw/9pfs/
@ -2263,7 +2263,6 @@ X: hw/9pfs/xen-9p*
F: fsdev/
F: tests/qtest/virtio-9p-test.c
F: tests/qtest/libqos/virtio-9p*
T: git https://gitlab.com/gkurz/qemu.git 9p-next
T: git https://github.com/cschoenebeck/qemu.git 9p.next
virtio-blk

3
hw/9pfs/9p-local.c
View File

@ -1538,6 +1538,9 @@ static int local_parse_opts(QemuOpts *opts, FsDriverEntry *fse, Error **errp)
"[remap|forbid|warn]\n");
return -1;
}
} else {
fse->export_flags &= ~V9FS_FORBID_MULTIDEVS;
fse->export_flags |= V9FS_REMAP_INODES;
}
if (!path) {

50
hw/9pfs/9p-util-generic.c Normal file
View File

@ -0,0 +1,50 @@
/* SPDX-License-Identifier: GPL-2.0-or-later */
#include "qemu/osdep.h"
#include "9p-util.h"
#include <glib/gstrfuncs.h>
char *qemu_open_flags_tostr(int flags)
{
int acc = flags & O_ACCMODE;
return g_strconcat(
(acc == O_WRONLY) ? "WRONLY" : (acc == O_RDONLY) ? "RDONLY" : "RDWR",
(flags & O_CREAT) ? "|CREAT" : "",
(flags & O_EXCL) ? "|EXCL" : "",
(flags & O_NOCTTY) ? "|NOCTTY" : "",
(flags & O_TRUNC) ? "|TRUNC" : "",
(flags & O_APPEND) ? "|APPEND" : "",
(flags & O_NONBLOCK) ? "|NONBLOCK" : "",
(flags & O_DSYNC) ? "|DSYNC" : "",
#ifdef O_DIRECT
(flags & O_DIRECT) ? "|DIRECT" : "",
#endif
(flags & O_LARGEFILE) ? "|LARGEFILE" : "",
(flags & O_DIRECTORY) ? "|DIRECTORY" : "",
(flags & O_NOFOLLOW) ? "|NOFOLLOW" : "",
#ifdef O_NOATIME
(flags & O_NOATIME) ? "|NOATIME" : "",
#endif
#ifdef O_CLOEXEC
(flags & O_CLOEXEC) ? "|CLOEXEC" : "",
#endif
#ifdef __O_SYNC
(flags & __O_SYNC) ? "|SYNC" : "",
#else
((flags & O_SYNC) == O_SYNC) ? "|SYNC" : "",
#endif
#ifdef O_PATH
(flags & O_PATH) ? "|PATH" : "",
#endif
#ifdef __O_TMPFILE
(flags & __O_TMPFILE) ? "|TMPFILE" : "",
#elif defined(O_TMPFILE)
((flags & O_TMPFILE) == O_TMPFILE) ? "|TMPFILE" : "",
#endif
/* O_NDELAY is usually just an alias of O_NONBLOCK */
#if defined(O_NDELAY) && O_NDELAY != O_NONBLOCK
(flags & O_NDELAY) ? "|NDELAY" : "",
#endif
NULL /* always last (required NULL termination) */
);
}

6
hw/9pfs/9p-util.h
View File

@ -267,4 +267,10 @@ int pthread_fchdir_np(int fd) __attribute__((weak_import));
#endif
int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev);
/*
* Returns a newly allocated string presentation of open() flags, intended
* for debugging (tracing) purposes only.
*/
char *qemu_open_flags_tostr(int flags);
#endif

45
hw/9pfs/9p.c
View File

@ -1774,6 +1774,21 @@ static bool same_stat_id(const struct stat *a, const struct stat *b)
return a->st_dev == b->st_dev && a->st_ino == b->st_ino;
}
/*
* Returns a (newly allocated) comma-separated string presentation of the
* passed array for logging (tracing) purpose for trace event "v9fs_walk".
*
* It is caller's responsibility to free the returned string.
*/
static char *trace_v9fs_walk_wnames(V9fsString *wnames, size_t nwnames)
{
g_autofree char **arr = g_malloc0_n(nwnames + 1, sizeof(char *));
for (size_t i = 0; i < nwnames; ++i) {
arr[i] = wnames[i].data;
}
return g_strjoinv(", ", arr);
}
static void coroutine_fn v9fs_walk(void *opaque)
{
int name_idx, nwalked;
@ -1787,6 +1802,7 @@ static void coroutine_fn v9fs_walk(void *opaque)
size_t offset = 7;
int32_t fid, newfid;
P9ARRAY_REF(V9fsString) wnames = NULL;
g_autofree char *trace_wnames = NULL;
V9fsFidState *fidp;
V9fsFidState *newfidp = NULL;
V9fsPDU *pdu = opaque;
@ -1800,11 +1816,9 @@ static void coroutine_fn v9fs_walk(void *opaque)
}
offset += err;
trace_v9fs_walk(pdu->tag, pdu->id, fid, newfid, nwnames);
if (nwnames > P9_MAXWELEM) {
err = -EINVAL;
goto out_nofid;
goto out_nofid_nownames;
}
if (nwnames) {
P9ARRAY_NEW(V9fsString, wnames, nwnames);
@ -1814,15 +1828,23 @@ static void coroutine_fn v9fs_walk(void *opaque)
for (i = 0; i < nwnames; i++) {
err = pdu_unmarshal(pdu, offset, "s", &wnames[i]);
if (err < 0) {
goto out_nofid;
goto out_nofid_nownames;
}
if (name_is_illegal(wnames[i].data)) {
err = -ENOENT;
goto out_nofid;
goto out_nofid_nownames;
}
offset += err;
}
if (trace_event_get_state_backends(TRACE_V9FS_WALK)) {
trace_wnames = trace_v9fs_walk_wnames(wnames, nwnames);
trace_v9fs_walk(pdu->tag, pdu->id, fid, newfid, nwnames,
trace_wnames);
}
} else {
trace_v9fs_walk(pdu->tag, pdu->id, fid, newfid, nwnames, "");
}
fidp = get_fid(pdu, fid);
if (fidp == NULL) {
err = -ENOENT;
@ -1957,7 +1979,11 @@ out:
}
v9fs_path_free(&dpath);
v9fs_path_free(&path);
goto out_pdu_complete;
out_nofid_nownames:
trace_v9fs_walk(pdu->tag, pdu->id, fid, newfid, nwnames, "<?>");
out_nofid:
out_pdu_complete:
pdu_complete(pdu, err);
}
@ -1982,6 +2008,7 @@ static void coroutine_fn v9fs_open(void *opaque)
V9fsFidState *fidp;
V9fsPDU *pdu = opaque;
V9fsState *s = pdu->s;
g_autofree char *trace_oflags = NULL;
if (s->proto_version == V9FS_PROTO_2000L) {
err = pdu_unmarshal(pdu, offset, "dd", &fid, &mode);
@ -1993,7 +2020,13 @@ static void coroutine_fn v9fs_open(void *opaque)
if (err < 0) {
goto out_nofid;
}
trace_v9fs_open(pdu->tag, pdu->id, fid, mode);
if (trace_event_get_state_backends(TRACE_V9FS_OPEN)) {
trace_oflags = qemu_open_flags_tostr(
(s->proto_version == V9FS_PROTO_2000L) ?
dotl_to_open_flags(mode) : omode_to_uflags(mode)
);
trace_v9fs_open(pdu->tag, pdu->id, fid, mode, trace_oflags);
}
fidp = get_fid(pdu, fid);
if (fidp == NULL) {

1
hw/9pfs/meson.build
View File

@ -3,6 +3,7 @@ fs_ss.add(files(
'9p-local.c',
'9p-posix-acl.c',
'9p-synth.c',
'9p-util-generic.c',
'9p-xattr-user.c',
'9p-xattr.c',
'9p.c',

4
hw/9pfs/trace-events
View File

@ -11,9 +11,9 @@ v9fs_stat(uint16_t tag, uint8_t id, int32_t fid) "tag %d id %d fid %d"
v9fs_stat_return(uint16_t tag, uint8_t id, int32_t mode, int32_t atime, int32_t mtime, int64_t length) "tag %d id %d stat={mode %d atime %d mtime %d length %"PRId64"}"
v9fs_getattr(uint16_t tag, uint8_t id, int32_t fid, uint64_t request_mask) "tag %d id %d fid %d request_mask %"PRIu64
v9fs_getattr_return(uint16_t tag, uint8_t id, uint64_t result_mask, uint32_t mode, uint32_t uid, uint32_t gid) "tag %d id %d getattr={result_mask %"PRId64" mode %u uid %u gid %u}"
v9fs_walk(uint16_t tag, uint8_t id, int32_t fid, int32_t newfid, uint16_t nwnames) "tag %d id %d fid %d newfid %d nwnames %d"
v9fs_walk(uint16_t tag, uint8_t id, int32_t fid, int32_t newfid, uint16_t nwnames, const char* wnames) "tag=%d id=%d fid=%d newfid=%d nwnames=%d wnames={%s}"
v9fs_walk_return(uint16_t tag, uint8_t id, uint16_t nwnames, void* qids) "tag %d id %d nwnames %d qids %p"
v9fs_open(uint16_t tag, uint8_t id, int32_t fid, int32_t mode) "tag %d id %d fid %d mode %d"
v9fs_open(uint16_t tag, uint8_t id, int32_t fid, int32_t mode, const char* oflags) "tag=%d id=%d fid=%d mode=%d(%s)"
v9fs_open_return(uint16_t tag, uint8_t id, uint8_t type, uint32_t version, uint64_t path, int iounit) "tag %u id %u qid={type %u version %u path %"PRIu64"} iounit %d"
v9fs_lcreate(uint16_t tag, uint8_t id, int32_t dfid, int32_t flags, int32_t mode, uint32_t gid) "tag %d id %d dfid %d flags %d mode %d gid %u"
v9fs_lcreate_return(uint16_t tag, uint8_t id, uint8_t type, uint32_t version, uint64_t path, int32_t iounit) "tag %u id %u qid={type %u version %u path %"PRIu64"} iounit %d"

49
qemu-options.hx
View File

@ -1951,32 +1951,37 @@ SRST
Specifies the tag name to be used by the guest to mount this
export point.
``multidevs=multidevs``
Specifies how to deal with multiple devices being shared with a
9p export. Supported behaviours are either "remap", "forbid" or
"warn". The latter is the default behaviour on which virtfs 9p
expects only one device to be shared with the same export, and
if more than one device is shared and accessed via the same 9p
export then only a warning message is logged (once) by qemu on
host side. In order to avoid file ID collisions on guest you
should either create a separate virtfs export for each device to
be shared with guests (recommended way) or you might use "remap"
instead which allows you to share multiple devices with only one
export instead, which is achieved by remapping the original
inode numbers from host to guest in a way that would prevent
such collisions. Remapping inodes in such use cases is required
``multidevs=remap|forbid|warn``
Specifies how to deal with multiple devices being shared with
the same 9p export in order to avoid file ID collisions on guest.
Supported behaviours are either "remap" (default), "forbid" or
"warn".
``remap`` : assumes the possibility that more than one device is
shared with the same 9p export. Therefore inode numbers from host
are remapped for guest in a way that would prevent file ID
collisions on guest. Remapping inodes in such cases is required
because the original device IDs from host are never passed and
exposed on guest. Instead all files of an export shared with
virtfs always share the same device id on guest. So two files
virtfs always share the same device ID on guest. So two files
with identical inode numbers but from actually different devices
on host would otherwise cause a file ID collision and hence
potential misbehaviours on guest. "forbid" on the other hand
assumes like "warn" that only one device is shared by the same
export, however it will not only log a warning message but also
deny access to additional devices on guest. Note though that
"forbid" does currently not block all possible file access
operations (e.g. readdir() would still return entries from other
devices).
potential severe misbehaviours on guest.
``warn`` : virtfs 9p expects only one device to be shared with
the same export. If however more than one device is shared and
accessed via the same 9p export then only a warning message is
logged (once) by qemu on host side. No further action is performed
in this case that would prevent file ID collisions on guest. This
could thus lead to severe misbehaviours in this case like wrong
files being accessed and data corruption on the exported tree.
``forbid`` : assumes like "warn" that only one device is shared
by the same 9p export, however it will not only log a warning
message but also deny access to additional devices on guest. Note
though that "forbid" does currently not block all possible file
access operations (e.g. readdir() would still return entries from
other devices).
ERST
DEF("iscsi", HAS_ARG, QEMU_OPTION_iscsi,