[PATCH v7 2/6] nvme-tcp: check page by sendpage_ok() before calling kernel_sendpage()

[Coly Li]

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 <col...@suse.de>
Cc: Chaitanya Kulkarni <chaitanya...@wdc.com>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Hannes Reinecke <ha...@suse.de>
Cc: Jan Kara <ja...@suse.com>
Cc: Jens Axboe <ax...@kernel.dk>
Cc: Mikhail Skorzhinskii <mskorz...@solarflare.com>
Cc: Philipp Reisner <philipp...@linbit.com>
Cc: Sagi Grimberg <sa...@grimberg.me>
Cc: Vlastimil Babka <vba...@suse.com>
Cc: sta...@vger.kernel.org
---
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