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 */
reiserfs_write_lock(struct super_block * s)21 void 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
reiserfs_write_unlock(struct super_block * s)34 void 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
51 /*
52 * If we already own the lock, just exit and don't increase the depth.
53 * Useful when we don't want to lock more than once.
54 *
55 * We always return the lock_depth we had before calling
56 * this function.
57 */
reiserfs_write_lock_once(struct super_block * s)58 int reiserfs_write_lock_once(struct super_block *s)
59 {
60 struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
61
62 if (sb_i->lock_owner != current) {
63 mutex_lock(&sb_i->lock);
64 sb_i->lock_owner = current;
65 return sb_i->lock_depth++;
66 }
67
68 return sb_i->lock_depth;
69 }
70
reiserfs_write_unlock_once(struct super_block * s,int lock_depth)71 void reiserfs_write_unlock_once(struct super_block *s, int lock_depth)
72 {
73 if (lock_depth == -1)
74 reiserfs_write_unlock(s);
75 }
76
77 /*
78 * Utility function to force a BUG if it is called without the superblock
79 * write lock held. caller is the string printed just before calling BUG()
80 */
reiserfs_check_lock_depth(struct super_block * sb,char * caller)81 void reiserfs_check_lock_depth(struct super_block *sb, char *caller)
82 {
83 struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
84
85 if (sb_i->lock_depth < 0)
86 reiserfs_panic(sb, "%s called without kernel lock held %d",
87 caller);
88 }
89
90 #ifdef CONFIG_REISERFS_CHECK
reiserfs_lock_check_recursive(struct super_block * sb)91 void reiserfs_lock_check_recursive(struct super_block *sb)
92 {
93 struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
94
95 WARN_ONCE((sb_i->lock_depth > 0), "Unwanted recursive reiserfs lock!\n");
96 }
97 #endif
98