1 #include <linux/reiserfs_fs.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 partialy based on the release while schedule() 19 * property of the Bkl. 20 */ 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 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 could even raise a BUG() if we don't 41 * want the data become corrupted 42 */ 43 WARN_ONCE(sb_i->lock_owner != current, 44 "Superblock write lock imbalance"); 45 46 if (--sb_i->lock_depth == -1) { 47 sb_i->lock_owner = NULL; 48 mutex_unlock(&sb_i->lock); 49 } 50 } 51 52 /* 53 * If we already own the lock, just exit and don't increase the depth. 54 * Useful when we don't want to lock more than once. 55 * 56 * We always return the lock_depth we had before calling 57 * this function. 58 */ 59 int reiserfs_write_lock_once(struct super_block *s) 60 { 61 struct reiserfs_sb_info *sb_i = REISERFS_SB(s); 62 63 if (sb_i->lock_owner != current) { 64 mutex_lock(&sb_i->lock); 65 sb_i->lock_owner = current; 66 return sb_i->lock_depth++; 67 } 68 69 return sb_i->lock_depth; 70 } 71 72 void reiserfs_write_unlock_once(struct super_block *s, int lock_depth) 73 { 74 if (lock_depth == -1) 75 reiserfs_write_unlock(s); 76 } 77 78 /* 79 * Utility function to force a BUG if it is called without the superblock 80 * write lock held. caller is the string printed just before calling BUG() 81 */ 82 void reiserfs_check_lock_depth(struct super_block *sb, char *caller) 83 { 84 struct reiserfs_sb_info *sb_i = REISERFS_SB(sb); 85 86 if (sb_i->lock_depth < 0) 87 reiserfs_panic(sb, "%s called without kernel lock held %d", 88 caller); 89 } 90