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
  62struct file_operations;
  63struct vfsmount;
  64struct dentry;
  65
  66#define rcu_dereference_check_fdtable(files, fdtfd) \
  67        rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
  68
  69#define files_fdtable(files) \
  70        rcu_dereference_check_fdtable((files), (files)->fdt)
  71
  72/*
  73 * The caller must ensure that fd table isn't shared or hold rcu or file lock
  74 */
  75static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
  76{
  77        struct fdtable *fdt = rcu_dereference_raw(files->fdt);
  78
  79        if (fd < fdt->max_fds)
  80                return rcu_dereference_raw(fdt->fd[fd]);
  81        return NULL;
  82}
  83
  84static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
  85{
  86        rcu_lockdep_assert(rcu_read_lock_held() ||
  87                           lockdep_is_held(&files->file_lock),
  88                           "suspicious rcu_dereference_check() usage");
  89        return __fcheck_files(files, fd);
  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 *);
 104void do_close_on_exec(struct files_struct *);
 105int iterate_fd(struct files_struct *, unsigned,
 106                int (*)(const void *, struct file *, unsigned),
 107                const void *);
 108
 109extern int __alloc_fd(struct files_struct *files,
 110                      unsigned start, unsigned end, unsigned flags);
 111extern void __fd_install(struct files_struct *files,
 112                      unsigned int fd, struct file *file);
 113extern int __close_fd(struct files_struct *files,
 114                      unsigned int fd);
 115
 116extern struct kmem_cache *files_cachep;
 117
 118#endif /* __LINUX_FDTABLE_H */
 119