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Commit 86f0afd4 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: fix ext4_discard_allocated_blocks() if we can't allocate the pa struct 



If there is a failure while allocating the preallocation structure, a
number of blocks can end up getting marked in the in-memory buddy
bitmap, and then not getting released.  This can result in the
following corruption getting reported by the kernel:

EXT4-fs error (device sda3): ext4_mb_generate_buddy:758: group 1126,
12793 clusters in bitmap, 12729 in gd

In that case, we need to release the blocks using mb_free_blocks().

Tested: fs smoke test; also demonstrated that with injected errors,
	the file system is no longer getting corrupted

Google-Bug-Id: 16657874

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
parent ee98fa3a

fs/ext4/mballoc.c

+20 −1
Original line number Diff line number Diff line
@@ -3217,8 +3217,27 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac) 
static void ext4_discard_allocated_blocks(struct ext4_allocation_context *ac)

{

	struct ext4_prealloc_space *pa = ac->ac_pa;

	struct ext4_buddy e4b;

	int err;



	if (pa && pa->pa_type == MB_INODE_PA)

	if (pa == NULL) {

		err = ext4_mb_load_buddy(ac->ac_sb, ac->ac_f_ex.fe_group, &e4b);

		if (err) {

			/*

			 * This should never happen since we pin the

			 * pages in the ext4_allocation_context so

			 * ext4_mb_load_buddy() should never fail.

			 */

			WARN(1, "mb_load_buddy failed (%d)", err);

			return;

		}

		ext4_lock_group(ac->ac_sb, ac->ac_f_ex.fe_group);

		mb_free_blocks(ac->ac_inode, &e4b, ac->ac_f_ex.fe_start,

			       ac->ac_f_ex.fe_len);

		ext4_unlock_group(ac->ac_sb, ac->ac_f_ex.fe_group);

		return;

	}

	if (pa->pa_type == MB_INODE_PA)

		pa->pa_free += ac->ac_b_ex.fe_len;

}