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 /*
  25  * The embedded_fd_set is a small fd_set,
  26  * suitable for most tasks (which open <= BITS_PER_LONG files)
  27  */
  28 struct embedded_fd_set {
  29         unsigned long fds_bits[1];
  30 };
  31
  32 struct 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  */
  44 struct 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                                lockdep_is_held(&(files)->file_lock) || \
  64                                atomic_read(&(files)->count) == 1 || \
  65                                rcu_my_thread_group_empty()))
  66
  67 #define files_fdtable(files) \
  68                 (rcu_dereference_check_fdtable((files), (files)->fdt))
  69
  70 struct file_operations;
  71 struct vfsmount;
  72 struct dentry;
  73
  74 extern int expand_files(struct files_struct *, int nr);
  75 extern void free_fdtable_rcu(struct rcu_head *rcu);
  76 extern void __init files_defer_init(void);
  77
  78 static inline void free_fdtable(struct fdtable *fdt)
  79 {
  80         call_rcu(&fdt->rcu, free_fdtable_rcu);
  81 }
  82
  83 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  84 {
  85         struct file * file = NULL;
  86         struct fdtable *fdt = files_fdtable(files);
  87
  88         if (fd < fdt->max_fds)
  89                 file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
  90         return file;
  91 }
  92
  93 /*
  94  * Check whether the specified fd has an open file.
  95  */
  96 #define fcheck(fd)      fcheck_files(current->files, fd)
  97
  98 struct task_struct;
  99
 100 struct files_struct *get_files_struct(struct task_struct *);
 101 void put_files_struct(struct files_struct *fs);
 102 void reset_files_struct(struct files_struct *);
 103 int unshare_files(struct files_struct **);
 104 struct files_struct *dup_fd(struct files_struct *, int *);
 105
 106 extern struct kmem_cache *files_cachep;
 107
 108 #endif /* __LINUX_FDTABLE_H */