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         unsigned long *full_fds_bits;
  30         struct rcu_head rcu;
  31 };
  32
  33 static inline bool close_on_exec(unsigned 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(unsigned 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         bool resize_in_progress;
  52         wait_queue_head_t resize_wait;
  53
  54         struct fdtable __rcu *fdt;
  55         struct fdtable fdtab;
  56   /*
  57    * written part on a separate cache line in SMP
  58    */
  59         spinlock_t file_lock ____cacheline_aligned_in_smp;
  60         unsigned int next_fd;
  61         unsigned long close_on_exec_init[1];
  62         unsigned long open_fds_init[1];
  63         unsigned long full_fds_bits_init[1];
  64         struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  65 };
  66
  67 struct file_operations;
  68 struct vfsmount;
  69 struct dentry;
  70
  71 #define rcu_dereference_check_fdtable(files, fdtfd) \
  72         rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
  73
  74 #define files_fdtable(files) \
  75         rcu_dereference_check_fdtable((files), (files)->fdt)
  76
  77 /*
  78  * The caller must ensure that fd table isn't shared or hold rcu or file lock
  79  */
  80 static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
  81 {
  82         struct fdtable *fdt = rcu_dereference_raw(files->fdt);
  83
  84         if (fd < fdt->max_fds) {
  85                 gmb();
  86                 return rcu_dereference_raw(fdt->fd[fd]);
  87         }
  88         return NULL;
  89 }
  90
  91 static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
  92 {
  93         RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
  94                            !lockdep_is_held(&files->file_lock),
  95                            "suspicious rcu_dereference_check() usage");
  96         return __fcheck_files(files, fd);
  97 }
  98
  99 /*
 100  * Check whether the specified fd has an open file.
 101  */
 102 #define fcheck(fd)      fcheck_files(current->files, fd)
 103
 104 struct task_struct;
 105
 106 struct files_struct *get_files_struct(struct task_struct *);
 107 void put_files_struct(struct files_struct *fs);
 108 void reset_files_struct(struct files_struct *);
 109 int unshare_files(struct files_struct **);
 110 struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
 111 void do_close_on_exec(struct files_struct *);
 112 int iterate_fd(struct files_struct *, unsigned,
 113                 int (*)(const void *, struct file *, unsigned),
 114                 const void *);
 115
 116 extern int __alloc_fd(struct files_struct *files,
 117                       unsigned start, unsigned end, unsigned flags);
 118 extern void __fd_install(struct files_struct *files,
 119                       unsigned int fd, struct file *file);
 120 extern int __close_fd(struct files_struct *files,
 121                       unsigned int fd);
 122
 123 extern struct kmem_cache *files_cachep;
 124
 125 #endif /* __LINUX_FDTABLE_H */