[ 03/82] md: protect against crash upon fsync on ro array

From: Ben Hutchings
Date: Mon Mar 18 2013 - 00:40:35 EST

3.2-stable review patch. If anyone has any objections, please let me know.


From: Sebastian Riemer <sebastian.riemer@xxxxxxxxxxxxxxxx>

commit bbfa57c0f2243a7c31fd248d22e9861a2802cad5 upstream.

If an fsync occurs on a read-only array, we need to send a
completion for the IO and may not increment the active IO count.
Otherwise, we hit a bug trace and can't stop the MD array anymore.

By advice of Christoph Hellwig we return success upon a flush
request but we return -EROFS for other writes.
We detect flush requests by checking if the bio has zero sectors.

This patch is suitable to any -stable kernel to which it applies.

Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Sebastian Riemer <sebastian.riemer@xxxxxxxxxxxxxxxx>
Reported-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Acked-by: Paul Menzel <paulepanter@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
drivers/md/md.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -345,6 +345,10 @@ static void md_make_request(struct reque
+ if (mddev->ro == 1 && unlikely(rw == WRITE)) {
+ bio_endio(bio, bio_sectors(bio) == 0 ? 0 : -EROFS);
+ return;
+ }
smp_rmb(); /* Ensure implications of 'active' are visible */
if (mddev->suspended) {

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/