[Devel] [PATCH hci-8.1 1/2] fs/fuse kio: don't spin on an empty iter in do_sockio_sendmsg()

From: Liu Kui <kui.liu@virtuozzo.com>
To: Konstantin Khorenko <khorenko@virtuozzo.com>
Cc: azaitsev@virtuozzo.com, devel@openvz.org,
	Liu Kui <kui.liu@virtuozzo.com>
Subject: [Devel] [PATCH hci-8.1 1/2] fs/fuse kio: don't spin on an empty iter in do_sockio_sendmsg()
Date: Thu, 01 Oct 2026 11:23:41 +0800	[thread overview]
Message-ID: <20261001-sockio-sendmsg-empty-iter-v1-1-b876f4fbb9c7@virtuozzo.com> (raw)
In-Reply-To: <20261001-sockio-sendmsg-empty-iter-v1-0-b876f4fbb9c7@virtuozzo.com>

If msg->get_iter() ever returns an empty iterator, do_sockio_sendmsg()
spins forever. Restore the old do_send_one_seg() behavior: warn and
fail the msg.

https://virtuozzo.atlassian.net/browse/VSTOR-142167

Fixes: 32b44dc7ba67 ("fs/fuse kio: refactor transmit path in pcs_sockio_send()")
Signed-off-by: Liu Kui <kui.liu@virtuozzo.com>
---
 fs/fuse/kio/pcs/pcs_sock_io.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/fuse/kio/pcs/pcs_sock_io.c b/fs/fuse/kio/pcs/pcs_sock_io.c
index 2da6d51c898b..b4a2ceeb331c 100644
--- a/fs/fuse/kio/pcs/pcs_sock_io.c
+++ b/fs/fuse/kio/pcs/pcs_sock_io.c
@@ -307,6 +307,11 @@ static int do_sockio_sendmsg(struct pcs_sockio *sio, struct pcs_msg *msg)
 		if (!iov_iter_count(it)) {
 			/* Current iter is exhausted, init new one */
 			msg->get_iter(msg, sio->write_offset, it, WRITE);
+			/* An empty iter here would spin this loop forever */
+			if (WARN_ON(!iov_iter_count(it))) {
+				clear_and_wake_up_bit(PCS_MSG_BUSY, &msg->flags);
+				return -PCS_ERR_NET_ABORT;
+			}
 		}
 
 		BUG_ON(iov_iter_count(it) > left);

-- 
Git-155)

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