1#include "reiserfs.h"
2#include <linux/mutex.h>
3
4/*
5 * The previous reiserfs locking scheme was heavily based on
6 * the tricky properties of the Bkl:
7 *
8 * - it was acquired recursively by a same task
9 * - the performances relied on the release-while-schedule() property
10 *
11 * Now that we replace it by a mutex, we still want to keep the same
12 * recursive property to avoid big changes in the code structure.
13 * We use our own lock_owner here because the owner field on a mutex
14 * is only available in SMP or mutex debugging, also we only need this field
15 * for this mutex, no need for a system wide mutex facility.
16 *
17 * Also this lock is often released before a call that could block because
18 * reiserfs performances were partially based on the release while schedule()
19 * property of the Bkl.
20 */
21void reiserfs_write_lock(struct super_block *s)
22{
23	struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
24
25	if (sb_i->lock_owner != current) {
26		mutex_lock(&sb_i->lock);
27		sb_i->lock_owner = current;
28	}
29
30	/* No need to protect it, only the current task touches it */
31	sb_i->lock_depth++;
32}
33
34void reiserfs_write_unlock(struct super_block *s)
35{
36	struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
37
38	/*
39	 * Are we unlocking without even holding the lock?
40	 * Such a situation must raise a BUG() if we don't want
41	 * to corrupt the data.
42	 */
43	BUG_ON(sb_i->lock_owner != current);
44
45	if (--sb_i->lock_depth == -1) {
46		sb_i->lock_owner = NULL;
47		mutex_unlock(&sb_i->lock);
48	}
49}
50
51int __must_check reiserfs_write_unlock_nested(struct super_block *s)
52{
53	struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
54	int depth;
55
56	/* this can happen when the lock isn't always held */
57	if (sb_i->lock_owner != current)
58		return -1;
59
60	depth = sb_i->lock_depth;
61
62	sb_i->lock_depth = -1;
63	sb_i->lock_owner = NULL;
64	mutex_unlock(&sb_i->lock);
65
66	return depth;
67}
68
69void reiserfs_write_lock_nested(struct super_block *s, int depth)
70{
71	struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
72
73	/* this can happen when the lock isn't always held */
74	if (depth == -1)
75		return;
76
77	mutex_lock(&sb_i->lock);
78	sb_i->lock_owner = current;
79	sb_i->lock_depth = depth;
80}
81
82/*
83 * Utility function to force a BUG if it is called without the superblock
84 * write lock held.  caller is the string printed just before calling BUG()
85 */
86void reiserfs_check_lock_depth(struct super_block *sb, char *caller)
87{
88	struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
89
90	WARN_ON(sb_i->lock_depth < 0);
91}
92
93#ifdef CONFIG_REISERFS_CHECK
94void reiserfs_lock_check_recursive(struct super_block *sb)
95{
96	struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
97
98	WARN_ONCE((sb_i->lock_depth > 0), "Unwanted recursive reiserfs lock!\n");
99}
100#endif
101