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