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#include <linux/fs.h>
  15
  16#include <linux/atomic.h>
  17
  18/*
  19 * The default fd array needs to be at least BITS_PER_LONG,
  20 * as this is the granularity returned by copy_fdset().
  21 */
  22#define NR_OPEN_DEFAULT BITS_PER_LONG
  23
  24struct fdtable {
  25        unsigned int max_fds;
  26        struct file __rcu **fd;      /* current fd array */
  27        unsigned long *close_on_exec;
  28        unsigned long *open_fds;
  29        struct rcu_head rcu;
  30};
  31
  32static inline bool close_on_exec(int fd, const struct fdtable *fdt)
  33{
  34        return test_bit(fd, fdt->close_on_exec);
  35}
  36
  37static inline bool fd_is_open(int fd, const struct fdtable *fdt)
  38{
  39        return test_bit(fd, fdt->open_fds);
  40}
  41
  42/*
  43 * Open file table structure
  44 */
  45struct files_struct {
  46  /*
  47   * read mostly part
  48   */
  49        atomic_t count;
  50        struct fdtable __rcu *fdt;
  51        struct fdtable fdtab;
  52  /*
  53   * written part on a separate cache line in SMP
  54   */
  55        spinlock_t file_lock ____cacheline_aligned_in_smp;
  56        int next_fd;
  57        unsigned long close_on_exec_init[1];
  58        unsigned long open_fds_init[1];
  59        struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  60};
  61
  62#define rcu_dereference_check_fdtable(files, fdtfd) \
  63        (rcu_dereference_check((fdtfd), \
  64                               lockdep_is_held(&(files)->file_lock) || \
  65                               atomic_read(&(files)->count) == 1 || \
  66                               rcu_my_thread_group_empty()))
  67
  68#define files_fdtable(files) \
  69                (rcu_dereference_check_fdtable((files), (files)->fdt))
  70
  71struct file_operations;
  72struct vfsmount;
  73struct dentry;
  74
  75extern void __init files_defer_init(void);
  76
  77static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  78{
  79        struct file * file = NULL;
  80        struct fdtable *fdt = files_fdtable(files);
  81
  82        if (fd < fdt->max_fds)
  83                file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
  84        return file;
  85}
  86
  87/*
  88 * Check whether the specified fd has an open file.
  89 */
  90#define fcheck(fd)      fcheck_files(current->files, fd)
  91
  92struct task_struct;
  93
  94struct files_struct *get_files_struct(struct task_struct *);
  95void put_files_struct(struct files_struct *fs);
  96void reset_files_struct(struct files_struct *);
  97int unshare_files(struct files_struct **);
  98struct files_struct *dup_fd(struct files_struct *, int *);
  99void do_close_on_exec(struct files_struct *);
 100int iterate_fd(struct files_struct *, unsigned,
 101                int (*)(const void *, struct file *, unsigned),
 102                const void *);
 103
 104extern int __alloc_fd(struct files_struct *files,
 105                      unsigned start, unsigned end, unsigned flags);
 106extern void __fd_install(struct files_struct *files,
 107                      unsigned int fd, struct file *file);
 108extern int __close_fd(struct files_struct *files,
 109                      unsigned int fd);
 110
 111extern struct kmem_cache *files_cachep;
 112
 113#endif /* __LINUX_FDTABLE_H */
 114