linux/include/linux/fdtable.h
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   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        struct fdtable *next;
  31};
  32
  33static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
  34{
  35        __set_bit(fd, fdt->close_on_exec);
  36}
  37
  38static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
  39{
  40        __clear_bit(fd, fdt->close_on_exec);
  41}
  42
  43static inline bool close_on_exec(int fd, const struct fdtable *fdt)
  44{
  45        return test_bit(fd, fdt->close_on_exec);
  46}
  47
  48static inline void __set_open_fd(int fd, struct fdtable *fdt)
  49{
  50        __set_bit(fd, fdt->open_fds);
  51}
  52
  53static inline void __clear_open_fd(int fd, struct fdtable *fdt)
  54{
  55        __clear_bit(fd, fdt->open_fds);
  56}
  57
  58static inline bool fd_is_open(int fd, const struct fdtable *fdt)
  59{
  60        return test_bit(fd, fdt->open_fds);
  61}
  62
  63/*
  64 * Open file table structure
  65 */
  66struct files_struct {
  67  /*
  68   * read mostly part
  69   */
  70        atomic_t count;
  71        struct fdtable __rcu *fdt;
  72        struct fdtable fdtab;
  73  /*
  74   * written part on a separate cache line in SMP
  75   */
  76        spinlock_t file_lock ____cacheline_aligned_in_smp;
  77        int next_fd;
  78        unsigned long close_on_exec_init[1];
  79        unsigned long open_fds_init[1];
  80        struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  81};
  82
  83#define rcu_dereference_check_fdtable(files, fdtfd) \
  84        (rcu_dereference_check((fdtfd), \
  85                               lockdep_is_held(&(files)->file_lock) || \
  86                               atomic_read(&(files)->count) == 1 || \
  87                               rcu_my_thread_group_empty()))
  88
  89#define files_fdtable(files) \
  90                (rcu_dereference_check_fdtable((files), (files)->fdt))
  91
  92struct file_operations;
  93struct vfsmount;
  94struct dentry;
  95
  96extern int expand_files(struct files_struct *, int nr);
  97extern void free_fdtable_rcu(struct rcu_head *rcu);
  98extern void __init files_defer_init(void);
  99
 100static inline void free_fdtable(struct fdtable *fdt)
 101{
 102        call_rcu(&fdt->rcu, free_fdtable_rcu);
 103}
 104
 105static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
 106{
 107        struct file * file = NULL;
 108        struct fdtable *fdt = files_fdtable(files);
 109
 110        if (fd < fdt->max_fds)
 111                file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
 112        return file;
 113}
 114
 115/*
 116 * Check whether the specified fd has an open file.
 117 */
 118#define fcheck(fd)      fcheck_files(current->files, fd)
 119
 120struct task_struct;
 121
 122struct files_struct *get_files_struct(struct task_struct *);
 123void put_files_struct(struct files_struct *fs);
 124void reset_files_struct(struct files_struct *);
 125int unshare_files(struct files_struct **);
 126struct files_struct *dup_fd(struct files_struct *, int *);
 127
 128extern struct kmem_cache *files_cachep;
 129
 130#endif /* __LINUX_FDTABLE_H */
 131
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