Re: [PATCH v5] md: protect against crash upon fsync on ro array

[Paul Menzel <pm.debian@googlemail.com>]

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Am Dienstag, den 29.01.2013, 12:19 +0100 schrieb Sebastian Riemer:

[…]

> Any further objection?

Small typo (occurs) in commit message.


Thanks,

Paul


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From adfac4df99edc1a83dced9c732464634d3381a9f Mon Sep 17 00:00:00 2001
From: Sebastian Riemer <sebastian.riemer@profitbricks.com>
Date: Fri, 25 Jan 2013 12:46:59 +0100
Subject: [PATCH v5] 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.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: NeilBrown <neilb@suse.de>
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>
---
 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 3db3d1b..1e634a6 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -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) {
-- 
1.7.1

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