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
  24 struct 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
  33 static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
  34 {
  35         __set_bit(fd, fdt->close_on_exec);
  36 }
  37
  38 static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
  39 {
  40         __clear_bit(fd, fdt->close_on_exec);
  41 }
  42
  43 static inline bool close_on_exec(int fd, const struct fdtable *fdt)
  44 {
  45         return test_bit(fd, fdt->close_on_exec);
  46 }
  47
  48 static inline void __set_open_fd(int fd, struct fdtable *fdt)
  49 {
  50         __set_bit(fd, fdt->open_fds);
  51 }
  52
  53 static inline void __clear_open_fd(int fd, struct fdtable *fdt)
  54 {
  55         __clear_bit(fd, fdt->open_fds);
  56 }
  57
  58 static 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  */
  66 struct 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
  92 struct file_operations;
  93 struct vfsmount;
  94 struct dentry;
  95
  96 extern int expand_files(struct files_struct *, int nr);
  97 extern void free_fdtable_rcu(struct rcu_head *rcu);
  98 extern void __init files_defer_init(void);
  99
 100 static inline void free_fdtable(struct fdtable *fdt)
 101 {
 102         call_rcu(&fdt->rcu, free_fdtable_rcu);
 103 }
 104
 105 static 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
 120 struct task_struct;
 121
 122 struct files_struct *get_files_struct(struct task_struct *);
 123 void put_files_struct(struct files_struct *fs);
 124 void reset_files_struct(struct files_struct *);
 125 int unshare_files(struct files_struct **);
 126 struct files_struct *dup_fd(struct files_struct *, int *);
 127
 128 extern struct kmem_cache *files_cachep;
 129
 130 #endif /* __LINUX_FDTABLE_H */