linux-kernel - [255/264] md/raid5: STRIPE_ACTIVE has lock semantics, add barriers

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Message-Id: <20111109213208.240820913@clark.kroah.org>
Date:	Wed, 09 Nov 2011 13:35:02 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Dan Williams <dan.j.williams@...el.com>,
	NeilBrown <neilb@...e.de>
Subject: [255/264] md/raid5: STRIPE_ACTIVE has lock semantics, add barriers

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

------------------

From: Dan Williams <dan.j.williams@...el.com>

commit 257a4b42af7586fab4eaec7f04e6896b86551843 upstream.

All updates that occur under STRIPE_ACTIVE should be globally visible
when STRIPE_ACTIVE clears.  test_and_set_bit() implies a barrier, but
clear_bit() does not.

This is suitable for 3.1-stable.

Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/md/raid5.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3116,7 +3116,7 @@ static void handle_stripe(struct stripe_
 	struct r5dev *pdev, *qdev;
 
 	clear_bit(STRIPE_HANDLE, &sh->state);
-	if (test_and_set_bit(STRIPE_ACTIVE, &sh->state)) {
+	if (test_and_set_bit_lock(STRIPE_ACTIVE, &sh->state)) {
 		/* already being handled, ensure it gets handled
 		 * again when current action finishes */
 		set_bit(STRIPE_HANDLE, &sh->state);
@@ -3381,7 +3381,7 @@ finish:
 
 	return_io(s.return_bi);
 
-	clear_bit(STRIPE_ACTIVE, &sh->state);
+	clear_bit_unlock(STRIPE_ACTIVE, &sh->state);
 }
 
 static void raid5_activate_delayed(raid5_conf_t *conf)


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