1 /*
2 * descriptor table internals; you almost certainly want file.h instead.
3 */
4
5 #ifndef __LINUX_FDTABLE_H
6 #define __LINUX_FDTABLE_H
7
8 #include <linux/posix_types.h>
9 #include <linux/compiler.h>
10 #include <linux/spinlock.h>
11 #include <linux/rcupdate.h>
12 #include <linux/types.h>
13 #include <linux/init.h>
14 #include <linux/fs.h>
15
16 #include <asm/atomic.h>
17
18 /*
19 * The default fd array needs to be at least BITS_PER_LONG,
20 * as this is the granularity returned by copy_fdset().
21 */
22 #define NR_OPEN_DEFAULT BITS_PER_LONG
23
24 /*
25 * The embedded_fd_set is a small fd_set,
26 * suitable for most tasks (which open <= BITS_PER_LONG files)
27 */
28 struct embedded_fd_set {
29 unsigned long fds_bits[1];
30 };
31
32 struct fdtable {
33 unsigned int max_fds;
34 struct file __rcu **fd; /* current fd array */
35 fd_set *close_on_exec;
36 fd_set *open_fds;
37 struct rcu_head rcu;
38 struct fdtable *next;
39 };
40
41 /*
42 * Open file table structure
43 */
44 struct files_struct {
45 /*
46 * read mostly part
47 */
48 atomic_t count;
49 struct fdtable __rcu *fdt;
50 struct fdtable fdtab;
51 /*
52 * written part on a separate cache line in SMP
53 */
54 spinlock_t file_lock ____cacheline_aligned_in_smp;
55 int next_fd;
56 struct embedded_fd_set close_on_exec_init;
57 struct embedded_fd_set open_fds_init;
58 struct file __rcu * fd_array[NR_OPEN_DEFAULT];
59 };
60
61 #define rcu_dereference_check_fdtable(files, fdtfd) \
62 (rcu_dereference_check((fdtfd), \
63 rcu_read_lock_held() || \
64 lockdep_is_held(&(files)->file_lock) || \
65 atomic_read(&(files)->count) == 1 || \
66 rcu_my_thread_group_empty()))
67
68 #define files_fdtable(files) \
69 (rcu_dereference_check_fdtable((files), (files)->fdt))
70
71 struct file_operations;
72 struct vfsmount;
73 struct dentry;
74
75 extern int expand_files(struct files_struct *, int nr);
76 extern void free_fdtable_rcu(struct rcu_head *rcu);
77 extern void __init files_defer_init(void);
78
free_fdtable(struct fdtable * fdt)79 static inline void free_fdtable(struct fdtable *fdt)
80 {
81 call_rcu(&fdt->rcu, free_fdtable_rcu);
82 }
83
fcheck_files(struct files_struct * files,unsigned int fd)84 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
85 {
86 struct file * file = NULL;
87 struct fdtable *fdt = files_fdtable(files);
88
89 if (fd < fdt->max_fds)
90 file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
91 return file;
92 }
93
94 /*
95 * Check whether the specified fd has an open file.
96 */
97 #define fcheck(fd) fcheck_files(current->files, fd)
98
99 struct task_struct;
100
101 struct files_struct *get_files_struct(struct task_struct *);
102 void put_files_struct(struct files_struct *fs);
103 void reset_files_struct(struct files_struct *);
104 int unshare_files(struct files_struct **);
105 struct files_struct *dup_fd(struct files_struct *, int *);
106
107 extern struct kmem_cache *files_cachep;
108
109 #endif /* __LINUX_FDTABLE_H */
110