linux-kernel - [ 30/47] dm mpath: check if scsi_dh module already loaded before trying to load

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Message-Id: <20120518212651.944059391@linuxfoundation.org>
Date:	Fri, 18 May 2012 14:27:19 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Ben Marzinski <bmarzins@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>,
	Alasdair G Kergon <agk@...hat.com>
Subject: [ 30/47] dm mpath: check if scsi_dh module already loaded before trying to load

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

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

From: Mike Snitzer <snitzer@...hat.com>

commit 510193a2d3d2e03ae53b95c0ae4f33cdff02cbf8 upstream.

If the requested scsi_dh module is already loaded then skip
request_module().

Multipath table loads can hang in an unnecessary __request_module.

Reported-by: Ben Marzinski <bmarzins@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Alasdair G Kergon <agk@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -698,8 +698,8 @@ static int parse_hw_handler(struct dm_ar
 		return 0;
 
 	m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
-	request_module("scsi_dh_%s", m->hw_handler_name);
-	if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
+	if (!try_then_request_module(scsi_dh_handler_exist(m->hw_handler_name),
+				     "scsi_dh_%s", m->hw_handler_name)) {
 		ti->error = "unknown hardware handler type";
 		ret = -EINVAL;
 		goto fail;


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