[PATCH] nilfs2: clear dirty flag on bdev buffers on log write failure

[Ryusuke Konishi <konishi.ryusuke@gmail.com>]

Since the commit referenced in the Fixes tag stopped directly calling
inode_attach_wb(), a dirty flag is set on buffers (with
mark_buffer_dirty()) allocated to the backing device for segment
summaries and the super root block during log writes.

While this dirty flag is cleared upon a successful log write, it remains
uncleared if the log write fails.

Consequently, when a log write fails, these backing device buffers are
left in an inconsistent state where their uptodate flag and the dirty
flag of the containing page/folio are cleared, but the buffer's dirty
flag remains as stale garbage.

Particularly when the block size is smaller than the page size, if other
buffers on the same page/folio become dirty, this buffer unexpectedly
becomes a target for writeback again.  As a result, if the block is
later reused for other data or metadata, that contents risks being
corrupted.

Fix this issue by calling clear_buffer_dirty() for the backing device
buffers when aborting log writes in nilfs_abort_logs().

Fixes: 68142cb628f7 ("nilfs2: do not call inode_attach_wb() directly")
Cc: stable@vger.kernel.org
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
---
Hi Viacheslav,

Please apply this bug fix.

This fixes an omitted clear of the dirty flag on backing device buffers,
which could cause an abnormal buffer state and potential block
overwriting data corruption.

Thanks,
Ryusuke Konishi

 fs/nilfs2/segment.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 829573cb6131..2f0e59847d02 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1829,6 +1829,7 @@ static void nilfs_abort_logs(struct list_head *logs, int err)
 	list_for_each_entry(segbuf, logs, sb_list) {
 		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
 				    b_assoc_buffers) {
+			clear_buffer_dirty(bh);
 			clear_buffer_uptodate(bh);
 			if (bh->b_folio != bd_folio) {
 				if (bd_folio)
@@ -1840,6 +1841,7 @@ static void nilfs_abort_logs(struct list_head *logs, int err)
 		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
 				    b_assoc_buffers) {
 			if (bh == segbuf->sb_super_root) {
+				clear_buffer_dirty(bh);
 				clear_buffer_uptodate(bh);
 				if (bh->b_folio != bd_folio) {
 					folio_end_writeback(bd_folio);
-- 
2.53.0