linux-kernel - [PATCH 3.16 122/217] USB: uas: Reduce can_queue to MAX

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Message-ID: <lsq.1461711741.995978802@decadent.org.uk>
Date:	Wed, 27 Apr 2016 01:02:21 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	"Hans de Goede" <hdegoede@...hat.com>
Subject: [PATCH 3.16 122/217] USB: uas: Reduce can_queue to MAX_CMNDS

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Hans de Goede <hdegoede@...hat.com>

commit 55ff8cfbc4e12a7d2187df523938cc671fbebdd1 upstream.

The uas driver can never queue more then MAX_CMNDS (- 1) tags and tags
are shared between luns, so there is no need to claim that we can_queue
some random large number.

Not claiming that we can_queue 65536 commands, fixes the uas driver
failing to initialize while allocating the tag map with a "Page allocation
failure (order 7)" error on systems which have been running for a while
and thus have fragmented memory.

Reported-and-tested-by: Yves-Alexis Perez <corsac@...sac.net>
Signed-off-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: add definition of MAX_CMNDS from upstream commit
 5e61aede477e ("uas: Do not use scsi_host_find_tag")]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/storage/uas.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/storage/uas.c
+++ b/drivers/usb/storage/uas.c
@@ -30,6 +30,8 @@
 #include "uas-detect.h"
 #include "scsiglue.h"
 
+#define MAX_CMNDS 256
+
 /*
  * The r00-r01c specs define this version of the SENSE IU data structure.
  * It's still in use by several different firmware releases.
@@ -991,7 +993,7 @@ static struct scsi_host_template uas_hos
 	.eh_abort_handler = uas_eh_abort_handler,
 	.eh_device_reset_handler = uas_eh_device_reset_handler,
 	.eh_bus_reset_handler = uas_eh_bus_reset_handler,
-	.can_queue = 65536,	/* Is there a limit on the _host_ ? */
+	.can_queue = MAX_CMNDS,
 	.this_id = -1,
 	.sg_tablesize = SG_NONE,
 	.cmd_per_lun = 1,	/* until we override it */
@@ -1057,7 +1059,7 @@ static int uas_configure_endpoints(struc
 		devinfo->use_streams = 0;
 	} else {
 		devinfo->qdepth = usb_alloc_streams(devinfo->intf, eps + 1,
-						    3, 256, GFP_NOIO);
+						    3, MAX_CMNDS, GFP_NOIO);
 		if (devinfo->qdepth < 0)
 			return devinfo->qdepth;
 		devinfo->use_streams = 1;