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 };
  31
  32 static inline bool close_on_exec(int fd, const struct fdtable *fdt)
  33 {
  34         return test_bit(fd, fdt->close_on_exec);
  35 }
  36
  37 static inline bool fd_is_open(int fd, const struct fdtable *fdt)
  38 {
  39         return test_bit(fd, fdt->open_fds);
  40 }
  41
  42 /*
  43  * Open file table structure
  44  */
  45 struct files_struct {
  46   /*
  47    * read mostly part
  48    */
  49         atomic_t count;
  50         struct fdtable __rcu *fdt;
  51         struct fdtable fdtab;
  52   /*
  53    * written part on a separate cache line in SMP
  54    */
  55         spinlock_t file_lock ____cacheline_aligned_in_smp;
  56         int next_fd;
  57         unsigned long close_on_exec_init[1];
  58         unsigned long open_fds_init[1];
  59         struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  60 };
  61
  62 #define rcu_dereference_check_fdtable(files, fdtfd) \
  63         (rcu_dereference_check((fdtfd), \
  64                                lockdep_is_held(&(files)->file_lock) || \
  65                                atomic_read(&(files)->count) == 1 || \
  66                                rcu_my_thread_group_empty()))
  67
  68 #define files_fdtable(files) \
  69                 (rcu_dereference_check_fdtable((files), (files)->fdt))
  70
  71 struct file_operations;
  72 struct vfsmount;
  73 struct dentry;
  74
  75 extern void __init files_defer_init(void);
  76
  77 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  78 {
  79         struct file * file = NULL;
  80         struct fdtable *fdt = files_fdtable(files);
  81
  82         if (fd < fdt->max_fds)
  83                 file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
  84         return file;
  85 }
  86
  87 /*
  88  * Check whether the specified fd has an open file.
  89  */
  90 #define fcheck(fd)      fcheck_files(current->files, fd)
  91
  92 struct task_struct;
  93
  94 struct files_struct *get_files_struct(struct task_struct *);
  95 void put_files_struct(struct files_struct *fs);
  96 void reset_files_struct(struct files_struct *);
  97 int unshare_files(struct files_struct **);
  98 struct files_struct *dup_fd(struct files_struct *, int *);
  99 void do_close_on_exec(struct files_struct *);
 100 int iterate_fd(struct files_struct *, unsigned,
 101                 int (*)(const void *, struct file *, unsigned),
 102                 const void *);
 103
 104 extern int __alloc_fd(struct files_struct *files,
 105                       unsigned start, unsigned end, unsigned flags);
 106 extern void __fd_install(struct files_struct *files,
 107                       unsigned int fd, struct file *file);
 108 extern int __close_fd(struct files_struct *files,
 109                       unsigned int fd);
 110
 111 extern struct kmem_cache *files_cachep;
 112
 113 #endif /* __LINUX_FDTABLE_H */