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Commit b90f6870 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

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

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: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent fd2dd9fb

fs/ext4/mballoc.c

+11 −10
Original line number Diff line number Diff line
@@ -2534,6 +2534,17 @@ 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);
@@ -2555,16 +2566,6 @@ 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;



			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);

		}

		kmem_cache_free(ext4_free_ext_cachep, entry);

		ext4_mb_release_desc(&e4b);

	}