ext4: Issue the discard operation *before* releasing the blocks to be reused

commit b90f687018e6d6c77d981b09203780f7001407e5 upstream (as of v2.6.34-rc6)

Otherwise, we can end up having data corruption because the blocks
could get reused and then discarded!

https://bugzilla.kernel.org/show_bug.cgi?id=15579

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 8216789d44462a10b74371834cf3daea15a18d11..65c2b79330e70957c6148b8b52e0d5033b34d150 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2537,6 +2537,17 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
                mb_debug(1, "gonna free %u blocks in group %u (0x%p):",
                         entry->count, entry->group, entry);
 
+               if (test_opt(sb, DISCARD)) {
+                       ext4_fsblk_t discard_block;
+
+                       discard_block = entry->start_blk +
+                               ext4_group_first_block_no(sb, entry->group);
+                       trace_ext4_discard_blocks(sb,
+                                       (unsigned long long)discard_block,
+                                       entry->count);
+                       sb_issue_discard(sb, discard_block, entry->count);
+               }
+
                err = ext4_mb_load_buddy(sb, entry->group, &e4b);
                /* we expect to find existing buddy because it's pinned */
                BUG_ON(err != 0);
@@ -2558,19 +2569,6 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
                        page_cache_release(e4b.bd_bitmap_page);
                }
                ext4_unlock_group(sb, entry->group);
-               if (test_opt(sb, DISCARD)) {
-                       ext4_fsblk_t discard_block;
-                       struct ext4_super_block *es = EXT4_SB(sb)->s_es;
-
-                       discard_block = (ext4_fsblk_t)entry->group *
-                                               EXT4_BLOCKS_PER_GROUP(sb)
-                                       + entry->start_blk
-                                       + le32_to_cpu(es->s_first_data_block);
-                       trace_ext4_discard_blocks(sb,
-                                       (unsigned long long)discard_block,
-                                       entry->count);
-                       sb_issue_discard(sb, discard_block, entry->count);
-               }
                kmem_cache_free(ext4_free_ext_cachep, entry);
                ext4_mb_release_desc(&e4b);
        }