linux-kernel - [PATCH 02/18] mg_disk: fix queue hang / infinite retry on !fs requests

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Date:	Fri,  8 May 2009 11:54:00 +0900
From:	Tejun Heo <tj@...nel.org>
To:	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-ide@...r.kernel.org, rusty@...tcorp.com.au,
	James.Bottomley@...senPartnership.com, mike.miller@...com,
	donari75@...il.com, paul.clements@...eleye.com, tim@...erelk.net,
	Geert.Uytterhoeven@...ycom.com, davem@...emloft.net,
	Laurent@...vier.info, jgarzik@...ox.com, jeremy@...source.com,
	grant.likely@...retlab.ca, adrian@...en.demon.co.uk,
	sfr@...b.auug.org.au, bzolnier@...il.com, petkovbb@...glemail.com,
	sshtylyov@...mvista.com, oakad@...oo.com, drzeus@...eus.cx,
	dwmw2@...radead.org, Markus.Lidel@...dowconnect.com,
	wein@...ibm.com, schwidefsky@...ibm.com, zaitcev@...hat.com,
	fujita.tomonori@....ntt.co.jp, axboe@...nel.dk
Cc:	Tejun Heo <tj@...nel.org>
Subject: [PATCH 02/18] mg_disk: fix queue hang / infinite retry on !fs requests

Both request functions in mg_disk simply return when they encounter a
!fs request, which means the request will never be cleared from the
queue causing queue hang and indefinite retry of the request.  Fix it.

While at it, flatten condition checks and add unlikely to !fs tests.

[ Impact: fix possible queue hang / infinite retry of !fs requests ]

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: unsik Kim <donari75@...il.com>
---
 drivers/block/mg_disk.c |   24 +++++++++++++-----------
 1 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/block/mg_disk.c b/drivers/block/mg_disk.c
index 826c349..be32388 100644
--- a/drivers/block/mg_disk.c
+++ b/drivers/block/mg_disk.c
@@ -672,16 +672,16 @@ static void mg_request_poll(struct request_queue *q)
 
 	while ((req = elv_next_request(q)) != NULL) {
 		host = req->rq_disk->private_data;
-		if (blk_fs_request(req)) {
-			switch (rq_data_dir(req)) {
-			case READ:
-				mg_read(req);
-				break;
-			case WRITE:
-				mg_write(req);
-				break;
-			}
+
+		if (unlikely(!blk_fs_request(req))) {
+			__blk_end_request_cur(req, -EIO);
+			continue;
 		}
+
+		if (rq_data_dir(req) == READ)
+			mg_read(req);
+		else
+			mg_write(req);
 	}
 }
 
@@ -766,8 +766,10 @@ static void mg_request(struct request_queue *q)
 			continue;
 		}
 
-		if (!blk_fs_request(req))
-			return;
+		if (unlikely(!blk_fs_request(req))) {
+			__blk_end_request_cur(req, -EIO);
+			continue;
+		}
 
 		if (!mg_issue_req(req, host, sect_num, sect_cnt))
 			return;
-- 
1.6.0.2

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