[PATCH] ubifs: drop false positive assertion

[PATCH] ubifs: drop false positive assertion

[Sascha Hauer]

The following sequence triggers

	ubifs_assert(c, c->lst.taken_empty_lebs > 0);

at the end of ubifs_remount_fs():

mount -t ubifs /dev/ubi0_0 /mnt
echo 1 > /sys/kernel/debug/ubifs/ubi0_0/ro_error
umount /mnt
mount -t ubifs -o ro /dev/ubix_y /mnt
mount -o remount,ro /mnt

The resulting

UBIFS assert failed in ubifs_remount_fs at 1878 (pid 161)

is a false positive. In the case above c->lst.taken_empty_lebs has
never been changed from its initial zero value. This will only happen
when the deferred recovery is done.

Fix this by doing the assertion only when recovery has been done
already.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 fs/ubifs/super.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 23e7042666a7..617197e35749 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1912,7 +1912,9 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
 		mutex_unlock(&c->bu_mutex);
 	}
 
-	ubifs_assert(c, c->lst.taken_empty_lebs > 0);
+	if (!c->need_recovery)
+		ubifs_assert(c, c->lst.taken_empty_lebs > 0);
+
 	return 0;
 }
 
-- 
2.18.0

Re: [PATCH] ubifs: drop false positive assertion

[Richard Weinberger]

Sascha,

Am Mittwoch, 12. September 2018, 14:51:38 CEST schrieb Sascha Hauer:
> The following sequence triggers
> 
> 	ubifs_assert(c, c->lst.taken_empty_lebs > 0);
> 
> at the end of ubifs_remount_fs():
> 
> mount -t ubifs /dev/ubi0_0 /mnt
> echo 1 > /sys/kernel/debug/ubifs/ubi0_0/ro_error
> umount /mnt
> mount -t ubifs -o ro /dev/ubix_y /mnt
> mount -o remount,ro /mnt

Ahh, ok. You have a unclean mount and then a read-only mount.
Therefore UBIFs is still not clean but cannot do anything about that.

> The resulting
> 
> UBIFS assert failed in ubifs_remount_fs at 1878 (pid 161)
> 
> is a false positive. In the case above c->lst.taken_empty_lebs has
> never been changed from its initial zero value. This will only happen
> when th> e deferred recovery is done.
> 
> Fix this by doing the assertion only when recovery has been done
> already.

Makes sense!

Thanks,
//richard