LXR linux/include/linux/fdtable.h

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