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
  15 #include <asm/atomic.h>
  16
  17 /*
  18  * The default fd array needs to be at least BITS_PER_LONG,
  19  * as this is the granularity returned by copy_fdset().
  20  */
  21 #define NR_OPEN_DEFAULT BITS_PER_LONG
  22
  23 /*
  24  * The embedded_fd_set is a small fd_set,
  25  * suitable for most tasks (which open <= BITS_PER_LONG files)
  26  */
  27 struct embedded_fd_set {
  28         unsigned long fds_bits[1];
  29 };
  30
  31 struct fdtable {
  32         unsigned int max_fds;
  33         struct file ** fd;      /* current fd array */
  34         fd_set *close_on_exec;
  35         fd_set *open_fds;
  36         struct rcu_head rcu;
  37         struct fdtable *next;
  38 };
  39
  40 /*
  41  * Open file table structure
  42  */
  43 struct files_struct {
  44   /*
  45    * read mostly part
  46    */
  47         atomic_t count;
  48         struct fdtable *fdt;
  49         struct fdtable fdtab;
  50   /*
  51    * written part on a separate cache line in SMP
  52    */
  53         spinlock_t file_lock ____cacheline_aligned_in_smp;
  54         int next_fd;
  55         struct embedded_fd_set close_on_exec_init;
  56         struct embedded_fd_set open_fds_init;
  57         struct file * fd_array[NR_OPEN_DEFAULT];
  58 };
  59
  60 #define rcu_dereference_check_fdtable(files, fdtfd) \
  61         (rcu_dereference_check((fdtfd), \
  62                                rcu_read_lock_held() || \
  63                                lockdep_is_held(&(files)->file_lock) || \
  64                                atomic_read(&(files)->count) == 1))
  65
  66 #define files_fdtable(files) \
  67                 (rcu_dereference_check_fdtable((files), (files)->fdt))
  68
  69 struct file_operations;
  70 struct vfsmount;
  71 struct dentry;
  72
  73 extern int expand_files(struct files_struct *, int nr);
  74 extern void free_fdtable_rcu(struct rcu_head *rcu);
  75 extern void __init files_defer_init(void);
  76
  77 static inline void free_fdtable(struct fdtable *fdt)
  78 {
  79         call_rcu(&fdt->rcu, free_fdtable_rcu);
  80 }
  81
  82 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  83 {
  84         struct file * file = NULL;
  85         struct fdtable *fdt = files_fdtable(files);
  86
  87         if (fd < fdt->max_fds)
  88                 file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
  89         return file;
  90 }
  91
  92 /*
  93  * Check whether the specified fd has an open file.
  94  */
  95 #define fcheck(fd)      fcheck_files(current->files, fd)
  96
  97 struct task_struct;
  98
  99 struct files_struct *get_files_struct(struct task_struct *);
 100 void put_files_struct(struct files_struct *fs);
 101 void reset_files_struct(struct files_struct *);
 102 int unshare_files(struct files_struct **);
 103 struct files_struct *dup_fd(struct files_struct *, int *);
 104
 105 extern struct kmem_cache *files_cachep;
 106
 107 #endif /* __LINUX_FDTABLE_H */