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        unsigned long *full_fds_bits;
  30        struct rcu_head rcu;
  31};
  32
  33static inline bool close_on_exec(int fd, const struct fdtable *fdt)
  34{
  35        return test_bit(fd, fdt->close_on_exec);
  36}
  37
  38static inline bool fd_is_open(int fd, const struct fdtable *fdt)
  39{
  40        return test_bit(fd, fdt->open_fds);
  41}
  42
  43/*
  44 * Open file table structure
  45 */
  46struct files_struct {
  47  /*
  48   * read mostly part
  49   */
  50        atomic_t count;
  51        bool resize_in_progress;
  52        wait_queue_head_t resize_wait;
  53
  54        struct fdtable __rcu *fdt;
  55        struct fdtable fdtab;
  56  /*
  57   * written part on a separate cache line in SMP
  58   */
  59        spinlock_t file_lock ____cacheline_aligned_in_smp;
  60        int next_fd;
  61        unsigned long close_on_exec_init[1];
  62        unsigned long open_fds_init[1];
  63        unsigned long full_fds_bits_init[1];
  64        struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  65};
  66
  67struct file_operations;
  68struct vfsmount;
  69struct dentry;
  70
  71#define rcu_dereference_check_fdtable(files, fdtfd) \
  72        rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
  73
  74#define files_fdtable(files) \
  75        rcu_dereference_check_fdtable((files), (files)->fdt)
  76
  77/*
  78 * The caller must ensure that fd table isn't shared or hold rcu or file lock
  79 */
  80static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
  81{
  82        struct fdtable *fdt = rcu_dereference_raw(files->fdt);
  83
  84        if (fd < fdt->max_fds)
  85                return rcu_dereference_raw(fdt->fd[fd]);
  86        return NULL;
  87}
  88
  89static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
  90{
  91        RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
  92                           !lockdep_is_held(&files->file_lock),
  93                           "suspicious rcu_dereference_check() usage");
  94        return __fcheck_files(files, fd);
  95}
  96
  97/*
  98 * Check whether the specified fd has an open file.
  99 */
 100#define fcheck(fd)      fcheck_files(current->files, fd)
 101
 102struct task_struct;
 103
 104struct files_struct *get_files_struct(struct task_struct *);
 105void put_files_struct(struct files_struct *fs);
 106void reset_files_struct(struct files_struct *);
 107int unshare_files(struct files_struct **);
 108struct files_struct *dup_fd(struct files_struct *, int *);
 109void do_close_on_exec(struct files_struct *);
 110int iterate_fd(struct files_struct *, unsigned,
 111                int (*)(const void *, struct file *, unsigned),
 112                const void *);
 113
 114extern int __alloc_fd(struct files_struct *files,
 115                      unsigned start, unsigned end, unsigned flags);
 116extern void __fd_install(struct files_struct *files,
 117                      unsigned int fd, struct file *file);
 118extern int __close_fd(struct files_struct *files,
 119                      unsigned int fd);
 120
 121extern struct kmem_cache *files_cachep;
 122
 123#endif /* __LINUX_FDTABLE_H */
 124