LXR linux/include/linux/file.h

   1/*
   2 * Wrapper functions for accessing the file_struct fd array.
   3 */
   4
   5#ifndef __LINUX_FILE_H
   6#define __LINUX_FILE_H
   7
   8#include <asm/atomic.h>
   9#include <linux/posix_types.h>
  10#include <linux/compiler.h>
  11#include <linux/spinlock.h>
  12#include <linux/rcupdate.h>
  13#include <linux/types.h>
  14
  15/*
  16 * The default fd array needs to be at least BITS_PER_LONG,
  17 * as this is the granularity returned by copy_fdset().
  18 */
  19#define NR_OPEN_DEFAULT BITS_PER_LONG
  20
  21/*
  22 * The embedded_fd_set is a small fd_set,
  23 * suitable for most tasks (which open <= BITS_PER_LONG files)
  24 */
  25struct embedded_fd_set {
  26        unsigned long fds_bits[1];
  27};
  28
  29/*
  30 * More than this number of fds: we use a separately allocated fd_set
  31 */
  32#define EMBEDDED_FD_SET_SIZE (BITS_PER_BYTE * sizeof(struct embedded_fd_set))
  33
  34struct fdtable {
  35        unsigned int max_fds;
  36        int max_fdset;
  37        struct file ** fd;      /* current fd array */
  38        fd_set *close_on_exec;
  39        fd_set *open_fds;
  40        struct rcu_head rcu;
  41        struct files_struct *free_files;
  42        struct fdtable *next;
  43};
  44
  45/*
  46 * Open file table structure
  47 */
  48struct files_struct {
  49  /*
  50   * read mostly part
  51   */
  52        atomic_t count;
  53        struct fdtable *fdt;
  54        struct fdtable fdtab;
  55  /*
  56   * written part on a separate cache line in SMP
  57   */
  58        spinlock_t file_lock ____cacheline_aligned_in_smp;
  59        int next_fd;
  60        struct embedded_fd_set close_on_exec_init;
  61        struct embedded_fd_set open_fds_init;
  62        struct file * fd_array[NR_OPEN_DEFAULT];
  63};
  64
  65#define files_fdtable(files) (rcu_dereference((files)->fdt))
  66
  67extern void FASTCALL(__fput(struct file *));
  68extern void FASTCALL(fput(struct file *));
  69
  70static inline void fput_light(struct file *file, int fput_needed)
  71{
  72        if (unlikely(fput_needed))
  73                fput(file);
  74}
  75
  76extern struct file * FASTCALL(fget(unsigned int fd));
  77extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
  78extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
  79extern void put_filp(struct file *);
  80extern int get_unused_fd(void);
  81extern void FASTCALL(put_unused_fd(unsigned int fd));
  82struct kmem_cache;
  83
  84extern struct file ** alloc_fd_array(int);
  85extern void free_fd_array(struct file **, int);
  86
  87extern fd_set *alloc_fdset(int);
  88extern void free_fdset(fd_set *, int);
  89
  90extern int expand_files(struct files_struct *, int nr);
  91extern void free_fdtable(struct fdtable *fdt);
  92extern void __init files_defer_init(void);
  93
  94static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  95{
  96        struct file * file = NULL;
  97        struct fdtable *fdt = files_fdtable(files);
  98
  99        if (fd < fdt->max_fds)
 100                file = rcu_dereference(fdt->fd[fd]);
 101        return file;
 102}
 103
 104/*
 105 * Check whether the specified fd has an open file.
 106 */
 107#define fcheck(fd)      fcheck_files(current->files, fd)
 108
 109extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
 110
 111struct task_struct;
 112
 113struct files_struct *get_files_struct(struct task_struct *);
 114void FASTCALL(put_files_struct(struct files_struct *fs));
 115
 116#endif /* __LINUX_FILE_H */
 117