ocfs2: fix leaf start calculation in ocfs2_dx_dir_rebalance()

ocfs2_dx_dir_rebalance() is passed the block offset of a dx leaf which needs
rebalancing. Since we rebalance an entire cluster at a time however, this
function needs to calculate the beginning of that cluster, in blocks. The
calculation was wrong, which would result in a read of non-leaf blocks. Fix
the calculation by adding ocfs2_block_to_cluster_start() which is a more
straight-forward way of determining this.

Reported-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index fa3c6d3f0bd2..e1844d5736c4 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -582,6 +582,16 @@ static inline u64 ocfs2_clusters_to_bytes(struct super_block *sb,
         return (u64)clusters << OCFS2_SB(sb)->s_clustersize_bits;
 }
 
+static inline u64 ocfs2_block_to_cluster_start(struct super_block *sb,
+                                               u64 blocks)
+{
+        int bits = OCFS2_SB(sb)->s_clustersize_bits - sb->s_blocksize_bits;
+        unsigned int clusters;
+
+        clusters = ocfs2_blocks_to_clusters(sb, blocks);
+        return (u64)clusters << bits;
+}
+
 static inline u64 ocfs2_align_bytes_to_clusters(struct super_block *sb,
                                                 u64 bytes)
 {