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 /*
  30  * More than this number of fds: we use a separately allocated fd_set
  31  */
  32 #define EMBEDDED_FD_SET_SIZE (BITS_PER_BYTE * sizeof(struct embedded_fd_set))
  33
  34 struct fdtable {
  35         unsigned int max_fds;
  36         int max_fdset;
  37         struct file ** fd;      /* current fd array */
  38         fd_set *close_on_exec;
  39         fd_set *open_fds;
  40         struct rcu_head rcu;
  41         struct files_struct *free_files;
  42         struct fdtable *next;
  43 };
  44
  45 /*
  46  * Open file table structure
  47  */
  48 struct files_struct {
  49   /*
  50    * read mostly part
  51    */
  52         atomic_t count;
  53         struct fdtable *fdt;
  54         struct fdtable fdtab;
  55   /*
  56    * written part on a separate cache line in SMP
  57    */
  58         spinlock_t file_lock ____cacheline_aligned_in_smp;
  59         int next_fd;
  60         struct embedded_fd_set close_on_exec_init;
  61         struct embedded_fd_set open_fds_init;
  62         struct file * fd_array[NR_OPEN_DEFAULT];
  63 };
  64
  65 #define files_fdtable(files) (rcu_dereference((files)->fdt))
  66
  67 extern void FASTCALL(__fput(struct file *));
  68 extern void FASTCALL(fput(struct file *));
  69
  70 static inline void fput_light(struct file *file, int fput_needed)
  71 {
  72         if (unlikely(fput_needed))
  73                 fput(file);
  74 }
  75
  76 extern struct file * FASTCALL(fget(unsigned int fd));
  77 extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
  78 extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
  79 extern void put_filp(struct file *);
  80 extern int get_unused_fd(void);
  81 extern void FASTCALL(put_unused_fd(unsigned int fd));
  82 struct kmem_cache;
  83
  84 extern struct file ** alloc_fd_array(int);
  85 extern void free_fd_array(struct file **, int);
  86
  87 extern fd_set *alloc_fdset(int);
  88 extern void free_fdset(fd_set *, int);
  89
  90 extern int expand_files(struct files_struct *, int nr);
  91 extern void free_fdtable(struct fdtable *fdt);
  92 extern void __init files_defer_init(void);
  93
  94 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  95 {
  96         struct file * file = NULL;
  97         struct fdtable *fdt = files_fdtable(files);
  98
  99         if (fd < fdt->max_fds)
 100                 file = rcu_dereference(fdt->fd[fd]);
 101         return file;
 102 }
 103
 104 /*
 105  * Check whether the specified fd has an open file.
 106  */
 107 #define fcheck(fd)      fcheck_files(current->files, fd)
 108
 109 extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
 110
 111 struct task_struct;
 112
 113 struct files_struct *get_files_struct(struct task_struct *);
 114 void FASTCALL(put_files_struct(struct files_struct *fs));
 115 void reset_files_struct(struct task_struct *, struct files_struct *);
 116
 117 #endif /* __LINUX_FILE_H */