LXR linux/include/linux/file.h

   1/*
   2 * Wrapper functions for accessing the file_struct fd array.
   3 */
   4
   5#ifndef __LINUX_FILE_H
   6#define __LINUX_FILE_H
   7
   8#include <asm/atomic.h>
   9#include <linux/posix_types.h>
  10#include <linux/compiler.h>
  11#include <linux/spinlock.h>
  12#include <linux/rcupdate.h>
  13#include <linux/types.h>
  14
  15/*
  16 * The default fd array needs to be at least BITS_PER_LONG,
  17 * as this is the granularity returned by copy_fdset().
  18 */
  19#define NR_OPEN_DEFAULT BITS_PER_LONG
  20
  21/*
  22 * The embedded_fd_set is a small fd_set,
  23 * suitable for most tasks (which open <= BITS_PER_LONG files)
  24 */
  25struct embedded_fd_set {
  26        unsigned long fds_bits[1];
  27};
  28
  29struct fdtable {
  30        unsigned int max_fds;
  31        struct file ** fd;      /* current fd array */
  32        fd_set *close_on_exec;
  33        fd_set *open_fds;
  34        struct rcu_head rcu;
  35        struct fdtable *next;
  36};
  37
  38/*
  39 * Open file table structure
  40 */
  41struct files_struct {
  42  /*
  43   * read mostly part
  44   */
  45        atomic_t count;
  46        struct fdtable *fdt;
  47        struct fdtable fdtab;
  48  /*
  49   * written part on a separate cache line in SMP
  50   */
  51        spinlock_t file_lock ____cacheline_aligned_in_smp;
  52        int next_fd;
  53        struct embedded_fd_set close_on_exec_init;
  54        struct embedded_fd_set open_fds_init;
  55        struct file * fd_array[NR_OPEN_DEFAULT];
  56};
  57
  58#define files_fdtable(files) (rcu_dereference((files)->fdt))
  59
  60extern struct kmem_cache *filp_cachep;
  61
  62extern void FASTCALL(__fput(struct file *));
  63extern void FASTCALL(fput(struct file *));
  64
  65static inline void fput_light(struct file *file, int fput_needed)
  66{
  67        if (unlikely(fput_needed))
  68                fput(file);
  69}
  70
  71extern struct file * FASTCALL(fget(unsigned int fd));
  72extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
  73extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
  74extern void put_filp(struct file *);
  75extern int get_unused_fd(void);
  76extern void FASTCALL(put_unused_fd(unsigned int fd));
  77struct kmem_cache;
  78
  79extern int expand_files(struct files_struct *, int nr);
  80extern void free_fdtable_rcu(struct rcu_head *rcu);
  81extern void __init files_defer_init(void);
  82
  83static inline void free_fdtable(struct fdtable *fdt)
  84{
  85        call_rcu(&fdt->rcu, free_fdtable_rcu);
  86}
  87
  88static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  89{
  90        struct file * file = NULL;
  91        struct fdtable *fdt = files_fdtable(files);
  92
  93        if (fd < fdt->max_fds)
  94                file = rcu_dereference(fdt->fd[fd]);
  95        return file;
  96}
  97
  98/*
  99 * Check whether the specified fd has an open file.
 100 */
 101#define fcheck(fd)      fcheck_files(current->files, fd)
 102
 103extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
 104
 105struct task_struct;
 106
 107struct files_struct *get_files_struct(struct task_struct *);
 108void FASTCALL(put_files_struct(struct files_struct *fs));
 109void reset_files_struct(struct task_struct *, struct files_struct *);
 110
 111extern struct kmem_cache *files_cachep;
 112
 113#endif /* __LINUX_FILE_H */
 114