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 <asm/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
  24/*
  25 * The embedded_fd_set is a small fd_set,
  26 * suitable for most tasks (which open <= BITS_PER_LONG files)
  27 */
  28struct embedded_fd_set {
  29        unsigned long fds_bits[1];
  30};
  31
  32struct fdtable {
  33        unsigned int max_fds;
  34        struct file __rcu **fd;      /* current fd array */
  35        fd_set *close_on_exec;
  36        fd_set *open_fds;
  37        struct rcu_head rcu;
  38        struct fdtable *next;
  39};
  40
  41/*
  42 * Open file table structure
  43 */
  44struct files_struct {
  45  /*
  46   * read mostly part
  47   */
  48        atomic_t count;
  49        struct fdtable __rcu *fdt;
  50        struct fdtable fdtab;
  51  /*
  52   * written part on a separate cache line in SMP
  53   */
  54        spinlock_t file_lock ____cacheline_aligned_in_smp;
  55        int next_fd;
  56        struct embedded_fd_set close_on_exec_init;
  57        struct embedded_fd_set open_fds_init;
  58        struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  59};
  60
  61#define rcu_dereference_check_fdtable(files, fdtfd) \
  62        (rcu_dereference_check((fdtfd), \
  63                               rcu_read_lock_held() || \
  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 int expand_files(struct files_struct *, int nr);
  76extern void free_fdtable_rcu(struct rcu_head *rcu);
  77extern void __init files_defer_init(void);
  78
  79static inline void free_fdtable(struct fdtable *fdt)
  80{
  81        call_rcu(&fdt->rcu, free_fdtable_rcu);
  82}
  83
  84static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  85{
  86        struct file * file = NULL;
  87        struct fdtable *fdt = files_fdtable(files);
  88
  89        if (fd < fdt->max_fds)
  90                file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
  91        return file;
  92}
  93
  94/*
  95 * Check whether the specified fd has an open file.
  96 */
  97#define fcheck(fd)      fcheck_files(current->files, fd)
  98
  99struct task_struct;
 100
 101struct files_struct *get_files_struct(struct task_struct *);
 102void put_files_struct(struct files_struct *fs);
 103void reset_files_struct(struct files_struct *);
 104int unshare_files(struct files_struct **);
 105struct files_struct *dup_fd(struct files_struct *, int *);
 106
 107extern struct kmem_cache *files_cachep;
 108
 109#endif /* __LINUX_FDTABLE_H */
 110