include/linux/file.h

   1 /*
   2  * Wrapper functions for accessing the file_struct fd array.
   3  */
   4
   5 #ifndef __LINUX_FILE_H
   6 #define __LINUX_FILE_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 extern struct kmem_cache *filp_cachep;
  61
  62 extern void FASTCALL(__fput(struct file *));
  63 extern void FASTCALL(fput(struct file *));
  64
  65 static inline void fput_light(struct file *file, int fput_needed)
  66 {
  67         if (unlikely(fput_needed))
  68                 fput(file);
  69 }
  70
  71 extern struct file * FASTCALL(fget(unsigned int fd));
  72 extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
  73 extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
  74 extern void put_filp(struct file *);
  75 extern int get_unused_fd(void);
  76 extern void FASTCALL(put_unused_fd(unsigned int fd));
  77 struct kmem_cache;
  78
  79 extern int expand_files(struct files_struct *, int nr);
  80 extern void free_fdtable_rcu(struct rcu_head *rcu);
  81 extern void __init files_defer_init(void);
  82
  83 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  84 {
  85         struct file * file = NULL;
  86         struct fdtable *fdt = files_fdtable(files);
  87
  88         if (fd < fdt->max_fds)
  89                 file = rcu_dereference(fdt->fd[fd]);
  90         return file;
  91 }
  92
  93 /*
  94  * Check whether the specified fd has an open file.
  95  */
  96 #define fcheck(fd)      fcheck_files(current->files, fd)
  97
  98 extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
  99
 100 struct task_struct;
 101
 102 struct files_struct *get_files_struct(struct task_struct *);
 103 void FASTCALL(put_files_struct(struct files_struct *fs));
 104 void reset_files_struct(struct task_struct *, struct files_struct *);
 105
 106 extern struct kmem_cache *files_cachep;
 107
 108 #endif /* __LINUX_FILE_H */