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         bool resize_in_progress;
  51         wait_queue_head_t resize_wait;
  52
  53         struct fdtable __rcu *fdt;
  54         struct fdtable fdtab;
  55   /*
  56    * written part on a separate cache line in SMP
  57    */
  58         spinlock_t file_lock ____cacheline_aligned_in_smp;
  59         int next_fd;
  60         unsigned long close_on_exec_init[1];
  61         unsigned long open_fds_init[1];
  62         struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  63 };
  64
  65 struct file_operations;
  66 struct vfsmount;
  67 struct dentry;
  68
  69 #define rcu_dereference_check_fdtable(files, fdtfd) \
  70         rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
  71
  72 #define files_fdtable(files) \
  73         rcu_dereference_check_fdtable((files), (files)->fdt)
  74
  75 /*
  76  * The caller must ensure that fd table isn't shared or hold rcu or file lock
  77  */
  78 static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
  79 {
  80         struct fdtable *fdt = rcu_dereference_raw(files->fdt);
  81
  82         if (fd < fdt->max_fds)
  83                 return rcu_dereference_raw(fdt->fd[fd]);
  84         return NULL;
  85 }
  86
  87 static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
  88 {
  89         rcu_lockdep_assert(rcu_read_lock_held() ||
  90                            lockdep_is_held(&files->file_lock),
  91                            "suspicious rcu_dereference_check() usage");
  92         return __fcheck_files(files, fd);
  93 }
  94
  95 /*
  96  * Check whether the specified fd has an open file.
  97  */
  98 #define fcheck(fd)      fcheck_files(current->files, fd)
  99
 100 struct task_struct;
 101
 102 struct files_struct *get_files_struct(struct task_struct *);
 103 void put_files_struct(struct files_struct *fs);
 104 void reset_files_struct(struct files_struct *);
 105 int unshare_files(struct files_struct **);
 106 struct files_struct *dup_fd(struct files_struct *, int *);
 107 void do_close_on_exec(struct files_struct *);
 108 int iterate_fd(struct files_struct *, unsigned,
 109                 int (*)(const void *, struct file *, unsigned),
 110                 const void *);
 111
 112 extern int __alloc_fd(struct files_struct *files,
 113                       unsigned start, unsigned end, unsigned flags);
 114 extern void __fd_install(struct files_struct *files,
 115                       unsigned int fd, struct file *file);
 116 extern int __close_fd(struct files_struct *files,
 117                       unsigned int fd);
 118
 119 extern struct kmem_cache *files_cachep;
 120
 121 #endif /* __LINUX_FDTABLE_H */