linux-kernel - [PATCH 4.2.y-ckt 40/70] rbd: use GFP_NOIO consistently for request allocations

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Message-Id: <1460494375-30070-41-git-send-email-kamal@canonical.com>
Date:	Tue, 12 Apr 2016 13:52:25 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	David Disseldorp <ddiss@...e.de>,
	Ilya Dryomov <idryomov@...il.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 40/70] rbd: use GFP_NOIO consistently for request allocations

4.2.8-ckt8 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: David Disseldorp <ddiss@...e.de>

commit 2224d879c7c0f85c14183ef82eb48bd875ceb599 upstream.

As of 5a60e87603c4c533492c515b7f62578189b03c9c, RBD object request
allocations are made via rbd_obj_request_create() with GFP_NOIO.
However, subsequent OSD request allocations in rbd_osd_req_create*()
use GFP_ATOMIC.

With heavy page cache usage (e.g. OSDs running on same host as krbd
client), rbd_osd_req_create() order-1 GFP_ATOMIC allocations have been
observed to fail, where direct reclaim would have allowed GFP_NOIO
allocations to succeed.

Suggested-by: Vlastimil Babka <vbabka@...e.cz>
Suggested-by: Neil Brown <neilb@...e.com>
Signed-off-by: David Disseldorp <ddiss@...e.de>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/block/rbd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 55f8a6a..5252117 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1955,7 +1955,7 @@ static struct ceph_osd_request *rbd_osd_req_create(
 
 	osdc = &rbd_dev->rbd_client->client->osdc;
 	osd_req = ceph_osdc_alloc_request(osdc, snapc, num_ops, false,
-					  GFP_ATOMIC);
+					  GFP_NOIO);
 	if (!osd_req)
 		return NULL;	/* ENOMEM */
 
@@ -2004,7 +2004,7 @@ rbd_osd_req_create_copyup(struct rbd_obj_request *obj_request)
 	rbd_dev = img_request->rbd_dev;
 	osdc = &rbd_dev->rbd_client->client->osdc;
 	osd_req = ceph_osdc_alloc_request(osdc, snapc, num_osd_ops,
-						false, GFP_ATOMIC);
+						false, GFP_NOIO);
 	if (!osd_req)
 		return NULL;	/* ENOMEM */
 
@@ -2503,7 +2503,7 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 					bio_chain_clone_range(&bio_list,
 								&bio_offset,
 								clone_size,
-								GFP_ATOMIC);
+								GFP_NOIO);
 			if (!obj_request->bio_list)
 				goto out_unwind;
 		} else if (type == OBJ_REQUEST_PAGES) {
-- 
2.7.4