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md: protect against crash upon fsync on ro array 

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@infradead.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: NeilBrown <neilb@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: Sebastian Riemer <sebastian.riemer@profitbricks.com>
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Paul Menzel <paulepanter@users.sourceforge.net>
Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
Sebastian Riemer 2013-02-21 13:28:09 +11:00 committed by NeilBrown
parent 19f949f525
commit bbfa57c0f2
1 changed files with 4 additions and 0 deletions
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4
drivers/md/md.c
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@ -307,6 +307,10 @@ static void md_make_request(struct request_queue *q, struct bio *bio)
bio_io_error(bio);
return;
}
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 */
rcu_read_lock();
if (mddev->suspended) {