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 extern void filp_ctor(void * objp, struct kmem_cache *cachep, unsigned long cflags);
  64 extern void filp_dtor(void * objp, struct kmem_cache *cachep, unsigned long dflags);
  65
  66 extern struct file ** alloc_fd_array(int);
  67 extern void free_fd_array(struct file **, int);
  68
  69 extern fd_set *alloc_fdset(int);
  70 extern void free_fdset(fd_set *, int);
  71
  72 extern int expand_files(struct files_struct *, int nr);
  73 extern void free_fdtable(struct fdtable *fdt);
  74 extern void __init files_defer_init(void);
  75
  76 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
  77 {
  78         struct file * file = NULL;
  79         struct fdtable *fdt = files_fdtable(files);
  80
  81         if (fd < fdt->max_fds)
  82                 file = rcu_dereference(fdt->fd[fd]);
  83         return file;
  84 }
  85
  86 /*
  87  * Check whether the specified fd has an open file.
  88  */
  89 #define fcheck(fd)      fcheck_files(current->files, fd)
  90
  91 extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
  92
  93 struct task_struct;
  94
  95 struct files_struct *get_files_struct(struct task_struct *);
  96 void FASTCALL(put_files_struct(struct files_struct *fs));
  97
  98 #endif /* __LINUX_FILE_H */