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 */
25struct 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
34struct 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 */
48struct 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
67extern void FASTCALL(__fput(struct file *));
68extern void FASTCALL(fput(struct file *));
69
70static inline void fput_light(struct file *file, int fput_needed)
71{
72	if (unlikely(fput_needed))
73		fput(file);
74}
75
76extern struct file * FASTCALL(fget(unsigned int fd));
77extern struct file * FASTCALL(fget_light(unsigned int fd, int *fput_needed));
78extern void FASTCALL(set_close_on_exec(unsigned int fd, int flag));
79extern void put_filp(struct file *);
80extern int get_unused_fd(void);
81extern void FASTCALL(put_unused_fd(unsigned int fd));
82struct kmem_cache;
83
84extern struct file ** alloc_fd_array(int);
85extern void free_fd_array(struct file **, int);
86
87extern fd_set *alloc_fdset(int);
88extern void free_fdset(fd_set *, int);
89
90extern int expand_files(struct files_struct *, int nr);
91extern void free_fdtable(struct fdtable *fdt);
92extern void __init files_defer_init(void);
93
94static 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
109extern void FASTCALL(fd_install(unsigned int fd, struct file * file));
110
111struct task_struct;
112
113struct files_struct *get_files_struct(struct task_struct *);
114void FASTCALL(put_files_struct(struct files_struct *fs));
115
116#endif /* __LINUX_FILE_H */
117