Re: [PATCH] nilfs2: fix missing continue after -ENOENT in nilfs_ioctl_mark_blocks_dirty()

[Junjie Cao]

Hi Ryusuke,

On Sat, 21 Mar 2026 at 02:32:05 +0900, Ryusuke Konishi wrote:
> Since this implementation interacts with userland GC, I will check
> whether this is a simple missing 'continue' statement or if it was
> intentional.

Both downstream paths have asserted on (ret == -ENOENT) since the
original commit 7942b919f732 -- initially as BUG_ON, later softened
to WARN_ON by 1f5abe7e7dbc.  If -ENOENT were meant to reach those
paths, asserting on it would be contradictory.

The original code appears to rely on the dead-block check
(bd_blocknr != bd_oblocknr) to implicitly skip the -ENOENT case,
which breaks when bd_oblocknr is also 0.

This same fix also resolves a related syzbot report that hits the
same root cause through the level-0 path (nilfs_mdt_get_block)
rather than nilfs_bmap_mark.  I applied the patch on top of
current master (bbeb83d3182a) and tested it locally against that
report's C reproducer in QEMU -- the warning no longer triggers.

  https://syzkaller.appspot.com/bug?extid=466a45fcfb0562f5b9a0

For that related report, when the patch is picked up:

  Reported-by: syzbot+466a45fcfb0562f5b9a0@xxxxxxxxxxxxxxxxxxxxxxxxx
  Closes: https://syzkaller.appspot.com/bug?extid=466a45fcfb0562f5b9a0
  Tested-by: Junjie Cao <junjie.cao@xxxxxxxxx>