ext4: Clarify the locking details in mballoc

[safe/jmp/linux-2.6] / fs / ext4 / mballoc.c

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 484c9d1..d23056d 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -928,8 +928,11 @@ int ext4_mb_init_group(struct super_block *sb, ext4_group_t group)
        blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
        this_grp = ext4_get_group_info(sb, group);
        /*
-        * This ensures we don't add group
-        * to this buddy cache via resize
+        * This ensures that we don't reinit the buddy cache
+        * page which map to the group from which we are already
+        * allocating. If we are looking at the buddy cache we would
+        * have taken a reference using ext4_mb_load_buddy and that
+        * would have taken the alloc_sem lock.
         */
        num_grp_locked =  ext4_mb_get_buddy_cache_lock(sb, group);
        if (!EXT4_MB_GRP_NEED_INIT(this_grp)) {