linux-kernel - [PATCH v5 2/3] nvme-tcp: check page by sendpage_ok() before calling kernel

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Message-Id: <20200816071518.6964-2-colyli@suse.de>
Date:   Sun, 16 Aug 2020 15:15:16 +0800
From:   Coly Li <colyli@...e.de>
To:     linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org
Cc:     netdev@...r.kernel.org, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, Coly Li <colyli@...e.de>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        Christoph Hellwig <hch@....de>, Hannes Reinecke <hare@...e.de>,
        Jan Kara <jack@...e.com>, Jens Axboe <axboe@...nel.dk>,
        Mikhail Skorzhinskii <mskorzhinskiy@...arflare.com>,
        Philipp Reisner <philipp.reisner@...bit.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Vlastimil Babka <vbabka@...e.com>
Subject: [PATCH v5 2/3] nvme-tcp: check page by sendpage_ok() before calling kernel_sendpage()

Currently nvme_tcp_try_send_data() doesn't use kernel_sendpage() to
send slab pages. But for pages allocated by __get_free_pages() without
__GFP_COMP, which also have refcount as 0, they are still sent by
kernel_sendpage() to remote end, this is problematic.

The new introduced helper sendpage_ok() checks both PageSlab tag and
page_count counter, and returns true if the checking page is OK to be
sent by kernel_sendpage().

This patch fixes the page checking issue of nvme_tcp_try_send_data()
with sendpage_ok(). If sendpage_ok() returns true, send this page by
kernel_sendpage(), otherwise use sock_no_sendpage to handle this page.

Signed-off-by: Coly Li <colyli@...e.de>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@....com>
Cc: Christoph Hellwig <hch@....de>
Cc: Hannes Reinecke <hare@...e.de>
Cc: Jan Kara <jack@...e.com>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Mikhail Skorzhinskii <mskorzhinskiy@...arflare.com>
Cc: Philipp Reisner <philipp.reisner@...bit.com>
Cc: Sagi Grimberg <sagi@...mberg.me>
Cc: Vlastimil Babka <vbabka@...e.com>
Cc: stable@...r.kernel.org
---
Changelog:
v4, change sendpage_ok() as an inline helper, and post it as
    separate patch.
v3, introduce a more common sendpage_ok()
v2, fix typo in patch subject
v1, the initial version.
 drivers/nvme/host/tcp.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 62fbaecdc960..902fe742762b 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -912,12 +912,11 @@ static int nvme_tcp_try_send_data(struct nvme_tcp_request *req)
 		else
 			flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
 
-		/* can't zcopy slab pages */
-		if (unlikely(PageSlab(page))) {
-			ret = sock_no_sendpage(queue->sock, page, offset, len,
+		if (sendpage_ok(page)) {
+			ret = kernel_sendpage(queue->sock, page, offset, len,
 					flags);
 		} else {
-			ret = kernel_sendpage(queue->sock, page, offset, len,
+			ret = sock_no_sendpage(queue->sock, page, offset, len,
 					flags);
 		}
 		if (ret <= 0)
-- 
2.26.2