Destructive writes to a block device on which nilfs2 is mounted can
cause a kernel bug in the folio/page writeback start routine or
writeback end routine (__folio_start_writeback in the log below):
kernel BUG at mm/page-writeback.c:3070!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
...
RIP: 0010:__folio_start_writeback+0xbaa/0x10e0
Code: 25 ff 0f 00 00 0f 84 18 01 00 00 e8 40 ca c6 ff e9 17 f6 ff ff
e8 36 ca c6 ff 4c 89 f7 48 c7 c6 80 c0 12 84 e8 e7 b3 0f 00 90 <0f>
0b e8 1f ca c6 ff 4c 89 f7 48 c7 c6 a0 c6 12 84 e8 d0 b3 0f 00
...
Call Trace:
<TASK>
nilfs_segctor_do_construct+0x4654/0x69d0 [nilfs2]
nilfs_segctor_construct+0x181/0x6b0 [nilfs2]
nilfs_segctor_thread+0x548/0x11c0 [nilfs2]
kthread+0x2f0/0x390
ret_from_fork+0x4b/0x80
ret_from_fork_asm+0x1a/0x30
</TASK>
This is because when the log writer starts a writeback for segment
summary blocks or a super root block that use the backing device's
page cache, it does not wait for the ongoing folio/page writeback,
resulting in an inconsistent writeback state.
Fix this issue by waiting for ongoing writebacks when putting
folios/pages on the backing device into writeback state.
Signed-off-by: Ryusuke Konishi <[email protected]>
Fixes: 9ff05123e3bf ("nilfs2: segment constructor")
Tested-by: Ryusuke Konishi <[email protected]>
Cc: [email protected]
---
Andrew, please apply this as a bug fix.
This fixes a kernel bug that is reproducible in some destructive testing.
Thanks,
Ryusuke Konishi
fs/nilfs2/segment.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 60d4f59f7665..6ea81f1d5094 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1652,6 +1652,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci)
if (bh->b_folio != bd_folio) {
if (bd_folio) {
folio_lock(bd_folio);
+ folio_wait_writeback(bd_folio);
folio_clear_dirty_for_io(bd_folio);
folio_start_writeback(bd_folio);
folio_unlock(bd_folio);
@@ -1665,6 +1666,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci)
if (bh == segbuf->sb_super_root) {
if (bh->b_folio != bd_folio) {
folio_lock(bd_folio);
+ folio_wait_writeback(bd_folio);
folio_clear_dirty_for_io(bd_folio);
folio_start_writeback(bd_folio);
folio_unlock(bd_folio);
@@ -1681,6 +1683,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci)
}
if (bd_folio) {
folio_lock(bd_folio);
+ folio_wait_writeback(bd_folio);
folio_clear_dirty_for_io(bd_folio);
folio_start_writeback(bd_folio);
folio_unlock(bd_folio);
--
2.34.1