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 struct file_operations;
  63 struct vfsmount;
  64 struct dentry;
  65
  66 #define rcu_dereference_check_fdtable(files, fdtfd) \
  67         rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
  68
  69 #define files_fdtable(files) \
  70         rcu_dereference_check_fdtable((files), (files)->fdt)
  71
  72 /*
  73  * The caller must ensure that fd table isn't shared or hold rcu or file lock
  74  */
  75 static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
  76 {
  77         struct fdtable *fdt = rcu_dereference_raw(files->fdt);
  78
  79         if (fd < fdt->max_fds)
  80                 return rcu_dereference_raw(fdt->fd[fd]);
  81         return NULL;
  82 }
  83
  84 static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
  85 {
  86         rcu_lockdep_assert(rcu_read_lock_held() ||
  87                            lockdep_is_held(&files->file_lock),
  88                            "suspicious rcu_dereference_check() usage");
  89         return __fcheck_files(files, fd);
  90 }
  91
  92 /*
  93  * Check whether the specified fd has an open file.
  94  */
  95 #define fcheck(fd)      fcheck_files(current->files, fd)
  96
  97 struct task_struct;
  98
  99 struct files_struct *get_files_struct(struct task_struct *);
 100 void put_files_struct(struct files_struct *fs);
 101 void reset_files_struct(struct files_struct *);
 102 int unshare_files(struct files_struct **);
 103 struct files_struct *dup_fd(struct files_struct *, int *);
 104 void do_close_on_exec(struct files_struct *);
 105 int iterate_fd(struct files_struct *, unsigned,
 106                 int (*)(const void *, struct file *, unsigned),
 107                 const void *);
 108
 109 extern int __alloc_fd(struct files_struct *files,
 110                       unsigned start, unsigned end, unsigned flags);
 111 extern void __fd_install(struct files_struct *files,
 112                       unsigned int fd, struct file *file);
 113 extern int __close_fd(struct files_struct *files,
 114                       unsigned int fd);
 115
 116 extern struct kmem_cache *files_cachep;
 117
 118 #endif /* __LINUX_FDTABLE_H */