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-rw-r--r--fs/reiserfs/stree.c42
1 files changed, 34 insertions, 8 deletions
diff --git a/fs/reiserfs/stree.c b/fs/reiserfs/stree.c
index 960c9114f6d..6b025a42d51 100644
--- a/fs/reiserfs/stree.c
+++ b/fs/reiserfs/stree.c
@@ -519,12 +519,22 @@ static int is_tree_node(struct buffer_head *bh, int level)
#define SEARCH_BY_KEY_READA 16
-/* The function is NOT SCHEDULE-SAFE! */
-static void search_by_key_reada(struct super_block *s,
+/*
+ * The function is NOT SCHEDULE-SAFE!
+ * It might unlock the write lock if we needed to wait for a block
+ * to be read. Note that in this case it won't recover the lock to avoid
+ * high contention resulting from too much lock requests, especially
+ * the caller (search_by_key) will perform other schedule-unsafe
+ * operations just after calling this function.
+ *
+ * @return true if we have unlocked
+ */
+static bool search_by_key_reada(struct super_block *s,
struct buffer_head **bh,
b_blocknr_t *b, int num)
{
int i, j;
+ bool unlocked = false;
for (i = 0; i < num; i++) {
bh[i] = sb_getblk(s, b[i]);
@@ -536,16 +546,21 @@ static void search_by_key_reada(struct super_block *s,
* the lock. But it's still fine because we check later
* if the tree changed
*/
- reiserfs_write_unlock(s);
for (j = 0; j < i; j++) {
/*
* note, this needs attention if we are getting rid of the BKL
* you have to make sure the prepared bit isn't set on this buffer
*/
- if (!buffer_uptodate(bh[j]))
+ if (!buffer_uptodate(bh[j])) {
+ if (!unlocked) {
+ reiserfs_write_unlock(s);
+ unlocked = true;
+ }
ll_rw_block(READA, 1, bh + j);
+ }
brelse(bh[j]);
}
+ return unlocked;
}
/**************************************************************************
@@ -633,15 +648,26 @@ int search_by_key(struct super_block *sb, const struct cpu_key *key, /* Key to s
have a pointer to it. */
if ((bh = last_element->pe_buffer =
sb_getblk(sb, block_number))) {
+ bool unlocked = false;
+
if (!buffer_uptodate(bh) && reada_count > 1)
- /* will unlock the write lock */
- search_by_key_reada(sb, reada_bh,
+ /* may unlock the write lock */
+ unlocked = search_by_key_reada(sb, reada_bh,
reada_blocks, reada_count);
- else
+ /*
+ * 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;
+ }
ll_rw_block(READ, 1, &bh);
wait_on_buffer(bh);
- reiserfs_write_lock(sb);
+
+ if (unlocked)
+ reiserfs_write_lock(sb);
if (!buffer_uptodate(bh))
goto io_error;
} else {