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/stree.c b/fs/reiserfs/stree.c
index 2f40a4c..4d7d476 100644
--- a/fs/reiserfs/stree.c
+++ b/fs/reiserfs/stree.c
@@ -524,14 +524,14 @@
* the caller (search_by_key) will perform other schedule-unsafe
* operations just after calling this function.
*
- * @return true if we have unlocked
+ * @return depth of lock to be restored after read completes
*/
-static bool search_by_key_reada(struct super_block *s,
+static int search_by_key_reada(struct super_block *s,
struct buffer_head **bh,
b_blocknr_t *b, int num)
{
int i, j;
- bool unlocked = false;
+ int depth = -1;
for (i = 0; i < num; i++) {
bh[i] = sb_getblk(s, b[i]);
@@ -549,15 +549,13 @@
* you have to make sure the prepared bit isn't set on this buffer
*/
if (!buffer_uptodate(bh[j])) {
- if (!unlocked) {
- reiserfs_write_unlock(s);
- unlocked = true;
- }
+ if (depth == -1)
+ depth = reiserfs_write_unlock_nested(s);
ll_rw_block(READA, 1, bh + j);
}
brelse(bh[j]);
}
- return unlocked;
+ return depth;
}
/**************************************************************************
@@ -645,26 +643,26 @@
have a pointer to it. */
if ((bh = last_element->pe_buffer =
sb_getblk(sb, block_number))) {
- bool unlocked = false;
+
+ /*
+ * We'll need to drop the lock if we encounter any
+ * buffers that need to be read. If all of them are
+ * already up to date, we don't need to drop the lock.
+ */
+ int depth = -1;
if (!buffer_uptodate(bh) && reada_count > 1)
- /* may unlock the write lock */
- unlocked = search_by_key_reada(sb, reada_bh,
+ depth = search_by_key_reada(sb, reada_bh,
reada_blocks, reada_count);
- /*
- * If we haven't already unlocked the write lock,
- * then we need to do that here before reading
- * the current block
- */
- if (!buffer_uptodate(bh) && !unlocked) {
- reiserfs_write_unlock(sb);
- unlocked = true;
- }
+
+ if (!buffer_uptodate(bh) && depth == -1)
+ depth = reiserfs_write_unlock_nested(sb);
+
ll_rw_block(READ, 1, &bh);
wait_on_buffer(bh);
- if (unlocked)
- reiserfs_write_lock(sb);
+ if (depth != -1)
+ reiserfs_write_lock_nested(sb, depth);
if (!buffer_uptodate(bh))
goto io_error;
} else {
@@ -1059,9 +1057,7 @@
reiserfs_free_block(th, inode, block, 1);
}
- reiserfs_write_unlock(sb);
- cond_resched();
- reiserfs_write_lock(sb);
+ reiserfs_cond_resched(sb);
if (item_moved (&s_ih, path)) {
need_re_search = 1;