4fd45812cb
An fdtable can either be embedded inside a files_struct or standalone (after being expanded). When an fdtable is being discarded after all RCU references to it have expired, we must either free it directly, in the standalone case, or free the files_struct it is contained within, in the embedded case. Currently the free_files field controls this behavior, but we can get rid of it entirely, as all the necessary information is already recorded. We can distinguish embedded and standalone fdtables using max_fds, and if it is embedded we can divine the relevant files_struct using container_of(). Signed-off-by: Vadim Lobanov <vlobanov@speakeasy.net> Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
115 lines
2.8 KiB
C
115 lines
2.8 KiB
C
/*
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* Wrapper functions for accessing the file_struct fd array.
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*/
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#ifndef __LINUX_FILE_H
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#define __LINUX_FILE_H
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#include <asm/atomic.h>
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#include <linux/posix_types.h>
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#include <linux/compiler.h>
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#include <linux/spinlock.h>
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#include <linux/rcupdate.h>
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#include <linux/types.h>
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/*
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* The default fd array needs to be at least BITS_PER_LONG,
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* as this is the granularity returned by copy_fdset().
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*/
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#define NR_OPEN_DEFAULT BITS_PER_LONG
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/*
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* The embedded_fd_set is a small fd_set,
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* suitable for most tasks (which open <= BITS_PER_LONG files)
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*/
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struct embedded_fd_set {
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unsigned long fds_bits[1];
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};
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struct fdtable {
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unsigned int max_fds;
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struct file ** fd; /* current fd array */
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fd_set *close_on_exec;
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fd_set *open_fds;
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struct rcu_head rcu;
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struct fdtable *next;
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};
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/*
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* Open file table structure
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*/
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struct files_struct {
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/*
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* read mostly part
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*/
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atomic_t count;
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struct fdtable *fdt;
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struct fdtable fdtab;
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/*
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* written part on a separate cache line in SMP
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*/
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spinlock_t file_lock ____cacheline_aligned_in_smp;
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int next_fd;
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struct embedded_fd_set close_on_exec_init;
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struct embedded_fd_set open_fds_init;
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struct file * fd_array[NR_OPEN_DEFAULT];
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};
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#define files_fdtable(files) (rcu_dereference((files)->fdt))
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extern struct kmem_cache *filp_cachep;
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extern void FASTCALL(__fput(struct file *));
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extern void FASTCALL(fput(struct file *));
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static inline void fput_light(struct file *file, int fput_needed)
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{
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if (unlikely(fput_needed))
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fput(file);
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}
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extern struct file * FASTCALL(fget(unsigned int fd));
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extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
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extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
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extern void put_filp(struct file *);
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extern int get_unused_fd(void);
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extern void FASTCALL(put_unused_fd(unsigned int fd));
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struct kmem_cache;
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extern struct file ** alloc_fd_array(int);
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extern void free_fd_array(struct file **, int);
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extern fd_set *alloc_fdset(int);
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extern void free_fdset(fd_set *, int);
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extern int expand_files(struct files_struct *, int nr);
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extern void free_fdtable_rcu(struct rcu_head *rcu);
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extern void __init files_defer_init(void);
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static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
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{
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struct file * file = NULL;
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struct fdtable *fdt = files_fdtable(files);
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if (fd < fdt->max_fds)
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file = rcu_dereference(fdt->fd[fd]);
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return file;
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}
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/*
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* Check whether the specified fd has an open file.
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*/
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#define fcheck(fd) fcheck_files(current->files, fd)
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extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
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struct task_struct;
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struct files_struct *get_files_struct(struct task_struct *);
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void FASTCALL(put_files_struct(struct files_struct *fs));
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void reset_files_struct(struct task_struct *, struct files_struct *);
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extern struct kmem_cache *files_cachep;
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#endif /* __LINUX_FILE_H */
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