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 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        struct fdtable __rcu *fdt;
  52        struct fdtable fdtab;
  53  /*
  54   * written part on a separate cache line in SMP
  55   */
  56        spinlock_t file_lock ____cacheline_aligned_in_smp;
  57        int next_fd;
  58        unsigned long close_on_exec_init[1];
  59        unsigned long open_fds_init[1];
  60        struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  61};
  62
  63#define rcu_dereference_check_fdtable(files, fdtfd) \
  64        (rcu_dereference_check((fdtfd), \
  65                               lockdep_is_held(&(files)->file_lock) || \
  66                               atomic_read(&(files)->count) == 1 || \
  67                               rcu_my_thread_group_empty()))
  68
  69#define files_fdtable(files) \
  70                (rcu_dereference_check_fdtable((files), (files)->fdt))
  71
  72struct file_operations;
  73struct vfsmount;
  74struct dentry;
  75
  76extern void __init files_defer_init(void);
  77
  78static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  79{
  80        struct file * file = NULL;
  81        struct fdtable *fdt = files_fdtable(files);
  82
  83        if (fd < fdt->max_fds)
  84                file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
  85        return file;
  86}
  87
  88/*
  89 * Check whether the specified fd has an open file.
  90 */
  91#define fcheck(fd)      fcheck_files(current->files, fd)
  92
  93struct task_struct;
  94
  95struct files_struct *get_files_struct(struct task_struct *);
  96void put_files_struct(struct files_struct *fs);
  97void reset_files_struct(struct files_struct *);
  98void daemonize_descriptors(void);
  99int unshare_files(struct files_struct **);
 100struct files_struct *dup_fd(struct files_struct *, int *);
 101void do_close_on_exec(struct files_struct *);
 102int iterate_fd(struct files_struct *, unsigned,
 103                int (*)(const void *, struct file *, unsigned),
 104                const void *);
 105
 106extern int __alloc_fd(struct files_struct *files,
 107                      unsigned start, unsigned end, unsigned flags);
 108extern void __fd_install(struct files_struct *files,
 109                      unsigned int fd, struct file *file);
 110extern int __close_fd(struct files_struct *files,
 111                      unsigned int fd);
 112
 113extern struct kmem_cache *files_cachep;
 114
 115#endif /* __LINUX_FDTABLE_H */
 116
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