reiserfs: locking, handle nested locks properly
The reiserfs write lock replaced the BKL and uses similar semantics.
Frederic's locking code makes a distinction between when the lock is nested
and when it's being acquired/released, but I don't think that's the right
distinction to make.
The right distinction is between the lock being released at end-of-use and
the lock being released for a schedule. The unlock should return the depth
and the lock should restore it, rather than the other way around as it is now.
This patch implements that and adds a number of places where the lock
should be dropped.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
diff --git a/fs/reiserfs/lock.c b/fs/reiserfs/lock.c
index d735bc8..045b83e 100644
--- a/fs/reiserfs/lock.c
+++ b/fs/reiserfs/lock.c
@@ -48,30 +48,35 @@
}
}
-/*
- * If we already own the lock, just exit and don't increase the depth.
- * Useful when we don't want to lock more than once.
- *
- * We always return the lock_depth we had before calling
- * this function.
- */
-int reiserfs_write_lock_once(struct super_block *s)
+int __must_check reiserfs_write_unlock_nested(struct super_block *s)
+{
+ struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
+ int depth;
+
+ /* this can happen when the lock isn't always held */
+ if (sb_i->lock_owner != current)
+ return -1;
+
+ depth = sb_i->lock_depth;
+
+ sb_i->lock_depth = -1;
+ sb_i->lock_owner = NULL;
+ mutex_unlock(&sb_i->lock);
+
+ return depth;
+}
+
+void reiserfs_write_lock_nested(struct super_block *s, int depth)
{
struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
- if (sb_i->lock_owner != current) {
- mutex_lock(&sb_i->lock);
- sb_i->lock_owner = current;
- return sb_i->lock_depth++;
- }
+ /* this can happen when the lock isn't always held */
+ if (depth == -1)
+ return;
- return sb_i->lock_depth;
-}
-
-void reiserfs_write_unlock_once(struct super_block *s, int lock_depth)
-{
- if (lock_depth == -1)
- reiserfs_write_unlock(s);
+ mutex_lock(&sb_i->lock);
+ sb_i->lock_owner = current;
+ sb_i->lock_depth = depth;
}
/*
@@ -82,9 +87,7 @@
{
struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
- if (sb_i->lock_depth < 0)
- reiserfs_panic(sb, "%s called without kernel lock held %d",
- caller);
+ WARN_ON(sb_i->lock_depth < 0);
}
#ifdef CONFIG_REISERFS_CHECK