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