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 bool close_on_exec(int fd, const struct fdtable *fdt)
  34 {
  35         return test_bit(fd, fdt->close_on_exec);
  36 }
  37
  38 static 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  */
  46 struct 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
  72 struct file_operations;
  73 struct vfsmount;
  74 struct dentry;
  75
  76 extern int expand_files(struct files_struct *, int nr);
  77 extern void __init files_defer_init(void);
  78
  79 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  80 {
  81         struct file * file = NULL;
  82         struct fdtable *fdt = files_fdtable(files);
  83
  84         if (fd < fdt->max_fds)
  85                 file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
  86         return file;
  87 }
  88
  89 /*
  90  * Check whether the specified fd has an open file.
  91  */
  92 #define fcheck(fd)      fcheck_files(current->files, fd)
  93
  94 struct task_struct;
  95
  96 struct files_struct *get_files_struct(struct task_struct *);
  97 void put_files_struct(struct files_struct *fs);
  98 void reset_files_struct(struct files_struct *);
  99 int unshare_files(struct files_struct **);
 100 struct files_struct *dup_fd(struct files_struct *, int *);
 101 void do_close_on_exec(struct files_struct *);
 102
 103 extern int __alloc_fd(struct files_struct *files,
 104                       unsigned start, unsigned end, unsigned flags);
 105 extern void __fd_install(struct files_struct *files,
 106                       unsigned int fd, struct file *file);
 107 extern int __close_fd(struct files_struct *files,
 108                       unsigned int fd);
 109
 110 extern struct kmem_cache *files_cachep;
 111
 112 #endif /* __LINUX_FDTABLE_H */