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 <asm/atomic.h>
   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
  15 /*
  16  * The default fd array needs to be at least BITS_PER_LONG,
  17  * as this is the granularity returned by copy_fdset().
  18  */
  19 #define NR_OPEN_DEFAULT BITS_PER_LONG
  20
  21 /*
  22  * The embedded_fd_set is a small fd_set,
  23  * suitable for most tasks (which open <= BITS_PER_LONG files)
  24  */
  25 struct embedded_fd_set {
  26         unsigned long fds_bits[1];
  27 };
  28
  29 struct fdtable {
  30         unsigned int max_fds;
  31         struct file ** fd;      /* current fd array */
  32         fd_set *close_on_exec;
  33         fd_set *open_fds;
  34         struct rcu_head rcu;
  35         struct fdtable *next;
  36 };
  37
  38 /*
  39  * Open file table structure
  40  */
  41 struct files_struct {
  42   /*
  43    * read mostly part
  44    */
  45         atomic_t count;
  46         struct fdtable *fdt;
  47         struct fdtable fdtab;
  48   /*
  49    * written part on a separate cache line in SMP
  50    */
  51         spinlock_t file_lock ____cacheline_aligned_in_smp;
  52         int next_fd;
  53         struct embedded_fd_set close_on_exec_init;
  54         struct embedded_fd_set open_fds_init;
  55         struct file * fd_array[NR_OPEN_DEFAULT];
  56 };
  57
  58 #define files_fdtable(files) (rcu_dereference((files)->fdt))
  59
  60 struct file_operations;
  61 struct vfsmount;
  62 struct dentry;
  63
  64 extern int expand_files(struct files_struct *, int nr);
  65 extern void free_fdtable_rcu(struct rcu_head *rcu);
  66 extern void __init files_defer_init(void);
  67
  68 static inline void free_fdtable(struct fdtable *fdt)
  69 {
  70         call_rcu(&fdt->rcu, free_fdtable_rcu);
  71 }
  72
  73 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  74 {
  75         struct file * file = NULL;
  76         struct fdtable *fdt = files_fdtable(files);
  77
  78         if (fd < fdt->max_fds)
  79                 file = rcu_dereference(fdt->fd[fd]);
  80         return file;
  81 }
  82
  83 /*
  84  * Check whether the specified fd has an open file.
  85  */
  86 #define fcheck(fd)      fcheck_files(current->files, fd)
  87
  88 struct task_struct;
  89
  90 struct files_struct *get_files_struct(struct task_struct *);
  91 void put_files_struct(struct files_struct *fs);
  92 void reset_files_struct(struct files_struct *);
  93 int unshare_files(struct files_struct **);
  94 struct files_struct *dup_fd(struct files_struct *, int *);
  95
  96 extern struct kmem_cache *files_cachep;
  97
  98 #endif /* __LINUX_FDTABLE_H */