Actually, Sebastian already sent an equivalent patch in <510AC77A.2000702@xxxxxxxxxxxxxxxx>. And he did test it. Here's his patch with the upstream reference added. Ben. -- Ben Hutchings Humans are not rational beings; they are rationalising beings.
From: Sebastian Riemer <sebastian.riemer@xxxxxxxxxxxxxxxx>
Date: Thu, 21 Feb 2013 13:28:09 +1100
Subject: md: protect against crash upon fsync on ro array
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.
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>
---
drivers/md/md.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 98262e5..4ef75e9 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -299,6 +299,10 @@ static int md_make_request(struct request_queue *q, struct bio *bio)
bio_io_error(bio);
return 0;
}
+ if (mddev->ro == 1 && unlikely(rw == WRITE)) {
+ bio_endio(bio, bio_sectors(bio) == 0 ? 0 : -EROFS);
+ return 0;
+ }
smp_rmb(); /* Ensure implications of 'active' are visible */
rcu_read_lock();
if (mddev->suspended) {
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