1 files changed, 34 insertions, 8 deletions

diff --git a/fs/reiserfs/stree.c b/fs/reiserfs/stree.c
index 960c9114f6d3..6b025a42d510 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 {