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 <linux/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 struct fdtable {
25 unsigned int max_fds;
26 struct file __rcu **fd; /* current fd array */
27 unsigned long *close_on_exec;
28 unsigned long *open_fds;
29 struct rcu_head rcu;
30 };
31
close_on_exec(int fd,const struct fdtable * fdt)32 static inline bool close_on_exec(int fd, const struct fdtable *fdt)
33 {
34 return test_bit(fd, fdt->close_on_exec);
35 }
36
fd_is_open(int fd,const struct fdtable * fdt)37 static inline bool fd_is_open(int fd, const struct fdtable *fdt)
38 {
39 return test_bit(fd, fdt->open_fds);
40 }
41
42 /*
43 * Open file table structure
44 */
45 struct files_struct {
46 /*
47 * read mostly part
48 */
49 atomic_t count;
50 struct fdtable __rcu *fdt;
51 struct fdtable fdtab;
52 /*
53 * written part on a separate cache line in SMP
54 */
55 spinlock_t file_lock ____cacheline_aligned_in_smp;
56 int next_fd;
57 unsigned long close_on_exec_init[1];
58 unsigned long open_fds_init[1];
59 struct file __rcu * fd_array[NR_OPEN_DEFAULT];
60 };
61
62 struct file_operations;
63 struct vfsmount;
64 struct dentry;
65
66 #define rcu_dereference_check_fdtable(files, fdtfd) \
67 rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
68
69 #define files_fdtable(files) \
70 rcu_dereference_check_fdtable((files), (files)->fdt)
71
72 /*
73 * The caller must ensure that fd table isn't shared or hold rcu or file lock
74 */
__fcheck_files(struct files_struct * files,unsigned int fd)75 static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
76 {
77 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
78
79 if (fd < fdt->max_fds)
80 return rcu_dereference_raw(fdt->fd[fd]);
81 return NULL;
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 rcu_lockdep_assert(rcu_read_lock_held() ||
87 lockdep_is_held(&files->file_lock),
88 "suspicious rcu_dereference_check() usage");
89 return __fcheck_files(files, fd);
90 }
91
92 /*
93 * Check whether the specified fd has an open file.
94 */
95 #define fcheck(fd) fcheck_files(current->files, fd)
96
97 struct task_struct;
98
99 struct files_struct *get_files_struct(struct task_struct *);
100 void put_files_struct(struct files_struct *fs);
101 void reset_files_struct(struct files_struct *);
102 int unshare_files(struct files_struct **);
103 struct files_struct *dup_fd(struct files_struct *, int *);
104 void do_close_on_exec(struct files_struct *);
105 int iterate_fd(struct files_struct *, unsigned,
106 int (*)(const void *, struct file *, unsigned),
107 const void *);
108
109 extern int __alloc_fd(struct files_struct *files,
110 unsigned start, unsigned end, unsigned flags);
111 extern void __fd_install(struct files_struct *files,
112 unsigned int fd, struct file *file);
113 extern int __close_fd(struct files_struct *files,
114 unsigned int fd);
115
116 extern struct kmem_cache *files_cachep;
117
118 #endif /* __LINUX_FDTABLE_H */
119