commit a4ca369ca221bb7e06c725792ac107f0e48e82e7 upstream.

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.

Link: https://lkml.kernel.org/r/20240530141556.4411-1-konishi.ryusuke@gmail.com Fixes: 9ff05123e3bf ("nilfs2: segment constructor") Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Tested-by: Ryusuke Konishi konishi.ryusuke@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org --- Please apply this patch to the stable trees indicated by the subject prefix instead of the patch that failed.

This patch is tailored to account for page/folio conversion and can be applied to v6.7 and earlier.

Also, all the builds and tests I did on each stable tree passed.

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 2d74fb229799..5783efafbabd 100644 --- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -1694,6 +1694,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci) if (bh->b_page != bd_page) { if (bd_page) { lock_page(bd_page); + wait_on_page_writeback(bd_page); clear_page_dirty_for_io(bd_page); set_page_writeback(bd_page); unlock_page(bd_page); @@ -1707,6 +1708,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci) if (bh == segbuf->sb_super_root) { if (bh->b_page != bd_page) { lock_page(bd_page); + wait_on_page_writeback(bd_page); clear_page_dirty_for_io(bd_page); set_page_writeback(bd_page); unlock_page(bd_page); @@ -1723,6 +1725,7 @@ static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci) } if (bd_page) { lock_page(bd_page); + wait_on_page_writeback(bd_page); clear_page_dirty_for_io(bd_page); set_page_writeback(bd_page); unlock_page(bd_page);