nilfs2: do not write dirty data after degenerating to read-only

commit 28a65b49eb53e172d23567005465019658bfdb4d upstream.

According to syzbot's report, mark_buffer_dirty() called from
nilfs_segctor_do_construct() outputs a warning with some patterns after
nilfs2 detects metadata corruption and degrades to read-only mode.

After such read-only degeneration, page cache data may be cleared through
nilfs_clear_dirty_page() which may also clear the uptodate flag for their
buffer heads.  However, even after the degeneration, log writes are still
performed by unmount processing etc., which causes mark_buffer_dirty() to
be called for buffer heads without the "uptodate" flag and causes the
warning.

Since any writes should not be done to a read-only file system in the
first place, this fixes the warning in mark_buffer_dirty() by letting
nilfs_segctor_do_construct() abort early if in read-only mode.

This also changes the retry check of nilfs_segctor_write_out() to avoid
unnecessary log write retries if it detects -EROFS that
nilfs_segctor_do_construct() returned.

Link: https://lkml.kernel.org/r/20230427011526.13457-1-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+2af3bc9585be7f23f290@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=2af3bc9585be7f23f290
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index b23ed9a35e5e47c65b4b8ba0d6237239e2244597..3091d1a3eddeaec68a65bf92fd8cc881b1d6bee6 100644 (file)
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -2039,6 +2039,9 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
        struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
        int err;
 
+       if (sb_rdonly(sci->sc_super))
+               return -EROFS;
+
        nilfs_sc_cstage_set(sci, NILFS_ST_INIT);
        sci->sc_cno = nilfs->ns_cno;
 
@@ -2724,7 +2727,7 @@ static void nilfs_segctor_write_out(struct nilfs_sc_info *sci)
 
                flush_work(&sci->sc_iput_work);
 
-       } while (ret && retrycount-- > 0);
+       } while (ret && ret != -EROFS && retrycount-- > 0);
 }
 
 /**