include/linux/fdtable.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * descriptor table internals; you almost certainly want file.h instead.
   4  */
   5
   6 #ifndef __LINUX_FDTABLE_H
   7 #define __LINUX_FDTABLE_H
   8
   9 #include <linux/posix_types.h>
  10 #include <linux/compiler.h>
  11 #include <linux/spinlock.h>
  12 #include <linux/rcupdate.h>
  13 #include <linux/types.h>
  14 #include <linux/init.h>
  15 #include <linux/fs.h>
  16
  17 #include <linux/atomic.h>
  18
  19 /*
  20  * The default fd array needs to be at least BITS_PER_LONG,
  21  * as this is the granularity returned by copy_fdset().
  22  */
  23 #define NR_OPEN_DEFAULT BITS_PER_LONG
  24
  25 struct fdtable {
  26         unsigned int max_fds;
  27         struct file __rcu **fd;      /* current fd array */
  28         unsigned long *close_on_exec;
  29         unsigned long *open_fds;
  30         unsigned long *full_fds_bits;
  31         struct rcu_head rcu;
  32 };
  33
  34 static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
  35 {
  36         return test_bit(fd, fdt->close_on_exec);
  37 }
  38
  39 static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
  40 {
  41         return test_bit(fd, fdt->open_fds);
  42 }
  43
  44 /*
  45  * Open file table structure
  46  */
  47 struct files_struct {
  48   /*
  49    * read mostly part
  50    */
  51         atomic_t count;
  52         bool resize_in_progress;
  53         wait_queue_head_t resize_wait;
  54
  55         struct fdtable __rcu *fdt;
  56         struct fdtable fdtab;
  57   /*
  58    * written part on a separate cache line in SMP
  59    */
  60         spinlock_t file_lock ____cacheline_aligned_in_smp;
  61         unsigned int next_fd;
  62         unsigned long close_on_exec_init[1];
  63         unsigned long open_fds_init[1];
  64         unsigned long full_fds_bits_init[1];
  65         struct file __rcu * fd_array[NR_OPEN_DEFAULT];
  66 };
  67
  68 struct file_operations;
  69 struct vfsmount;
  70 struct dentry;
  71
  72 #define rcu_dereference_check_fdtable(files, fdtfd) \
  73         rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
  74
  75 #define files_fdtable(files) \
  76         rcu_dereference_check_fdtable((files), (files)->fdt)
  77
  78 /*
  79  * The caller must ensure that fd table isn't shared or hold rcu or file lock
  80  */
  81 static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
  82 {
  83         struct fdtable *fdt = rcu_dereference_raw(files->fdt);
  84
  85         if (fd < fdt->max_fds)
  86                 return rcu_dereference_raw(fdt->fd[fd]);
  87         return NULL;
  88 }
  89
  90 static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
  91 {
  92         RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
  93                            !lockdep_is_held(&files->file_lock),
  94                            "suspicious rcu_dereference_check() usage");
  95         return __fcheck_files(files, fd);
  96 }
  97
  98 /*
  99  * Check whether the specified fd has an open file.
 100  */
 101 #define fcheck(fd)      fcheck_files(current->files, fd)
 102
 103 struct task_struct;
 104
 105 struct files_struct *get_files_struct(struct task_struct *);
 106 void put_files_struct(struct files_struct *fs);
 107 void reset_files_struct(struct files_struct *);
 108 int unshare_files(struct files_struct **);
 109 struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
 110 void do_close_on_exec(struct files_struct *);
 111 int iterate_fd(struct files_struct *, unsigned,
 112                 int (*)(const void *, struct file *, unsigned),
 113                 const void *);
 114
 115 extern int __alloc_fd(struct files_struct *files,
 116                       unsigned start, unsigned end, unsigned flags);
 117 extern void __fd_install(struct files_struct *files,
 118                       unsigned int fd, struct file *file);
 119 extern int __close_fd(struct files_struct *files,
 120                       unsigned int fd);
 121
 122 extern struct kmem_cache *files_cachep;
 123
 124 #endif /* __LINUX_FDTABLE_H */