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: "Theodore Ts'o" <tytso@xxxxxxx>
---
fs/ext4/mballoc.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index ced8bcb..4d7a6c4 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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;
}
--
2.0.0
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