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
  14 /*
  15  * The default fd array needs to be at least BITS_PER_LONG,
  16  * as this is the granularity returned by copy_fdset().
  17  */
  18 #define NR_OPEN_DEFAULT BITS_PER_LONG
  19
  20 struct fdtable {
  21         unsigned int max_fds;
  22         int max_fdset;
  23         int next_fd;
  24         struct file ** fd;      /* current fd array */
  25         fd_set *close_on_exec;
  26         fd_set *open_fds;
  27         struct rcu_head rcu;
  28         struct files_struct *free_files;
  29         struct fdtable *next;
  30 };
  31
  32 /*
  33  * Open file table structure
  34  */
  35 struct files_struct {
  36         atomic_t count;
  37         struct fdtable *fdt;
  38         struct fdtable fdtab;
  39         fd_set close_on_exec_init;
  40         fd_set open_fds_init;
  41         struct file * fd_array[NR_OPEN_DEFAULT];
  42         spinlock_t file_lock;     /* Protects concurrent writers.  Nests inside tsk->alloc_lock */
  43 };
  44
  45 #define files_fdtable(files) (rcu_dereference((files)->fdt))
  46
  47 extern void FASTCALL(__fput(struct file *));
  48 extern void FASTCALL(fput(struct file *));
  49
  50 static inline void fput_light(struct file *file, int fput_needed)
  51 {
  52         if (unlikely(fput_needed))
  53                 fput(file);
  54 }
  55
  56 extern struct file * FASTCALL(fget(unsigned int fd));
  57 extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
  58 extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
  59 extern void put_filp(struct file *);
  60 extern int get_unused_fd(void);
  61 extern void FASTCALL(put_unused_fd(unsigned int fd));
  62 struct kmem_cache;
  63
  64 extern struct file ** alloc_fd_array(int);
  65 extern void free_fd_array(struct file **, int);
  66
  67 extern fd_set *alloc_fdset(int);
  68 extern void free_fdset(fd_set *, int);
  69
  70 extern int expand_files(struct files_struct *, int nr);
  71 extern void free_fdtable(struct fdtable *fdt);
  72 extern void __init files_defer_init(void);
  73
  74 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  75 {
  76         struct file * file = NULL;
  77         struct fdtable *fdt = files_fdtable(files);
  78
  79         if (fd < fdt->max_fds)
  80                 file = rcu_dereference(fdt->fd[fd]);
  81         return file;
  82 }
  83
  84 /*
  85  * Check whether the specified fd has an open file.
  86  */
  87 #define fcheck(fd)      fcheck_files(current->files, fd)
  88
  89 extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
  90
  91 struct task_struct;
  92
  93 struct files_struct *get_files_struct(struct task_struct *);
  94 void FASTCALL(put_files_struct(struct files_struct *fs));
  95
  96 #endif /* __LINUX_FILE_H */