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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2009-09-09 23:50:17 -0400
committerTheodore Ts'o <tytso@mit.edu>2009-09-09 23:50:17 -0400
commit08c3a8133810d955d97f7146c50c43e4073f2148 (patch)
tree7caab5e454cdfc39817bd34b9a5be21743af5771 /fs/ext4/mballoc.c
parentf41c0750538667b87a19c93952e5d42fcc069bd7 (diff)
ext4: Clarify the locking details in mballoc
We don't need to take the alloc_sem lock when we are adding new groups, since mballoc won't see the new group added until we bump sbi->s_groups_count. Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Diffstat (limited to 'fs/ext4/mballoc.c')
-rw-r--r--fs/ext4/mballoc.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 484c9d10c7f..d23056d375b 100644
--- 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)) {