Unverified Commit 0e764b9d authored by David Howells's avatar David Howells Committed by Christian Brauner
Browse files

netfs: Fix the handling of stream->front by removing it 



The netfs_io_stream::front member is meant to point to the subrequest
currently being collected on a stream, but it isn't actually used this way
by direct write (which mostly ignores it).  However, there's a tracepoint
which looks at it.  Further, stream->front is actually redundant with
stream->subrequests.next.

Fix the potential problem in the direct code by just removing the member
and using stream->subrequests.next instead, thereby also simplifying the
code.

Fixes: a0b4c7a4 ("netfs: Fix unbuffered/DIO writes to dispatch subrequests in strict sequence")
Reported-by: default avatarPaulo Alcantara <pc@manguebit.org>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/4158599.1774426817@warthog.procyon.org.uk


Reviewed-by: default avatarPaulo Alcantara (Red Hat) <pc@manguebit.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent f621324d

fs/netfs/buffered_read.c

+1 −2
Original line number Diff line number Diff line
@@ -171,9 +171,8 @@ static void netfs_queue_read(struct netfs_io_request *rreq, 
	spin_lock(&rreq->lock);

	list_add_tail(&subreq->rreq_link, &stream->subrequests);

	if (list_is_first(&subreq->rreq_link, &stream->subrequests)) {

		stream->front = subreq;

		if (!stream->active) {

			stream->collected_to = stream->front->start;

			stream->collected_to = subreq->start;

			/* Store list pointers before active flag */

			smp_store_release(&stream->active, true);

		}

fs/netfs/direct_read.c

+1 −2
Original line number Diff line number Diff line
@@ -71,9 +71,8 @@ static int netfs_dispatch_unbuffered_reads(struct netfs_io_request *rreq) 
		spin_lock(&rreq->lock);

		list_add_tail(&subreq->rreq_link, &stream->subrequests);

		if (list_is_first(&subreq->rreq_link, &stream->subrequests)) {

			stream->front = subreq;

			if (!stream->active) {

				stream->collected_to = stream->front->start;

				stream->collected_to = subreq->start;

				/* Store list pointers before active flag */

				smp_store_release(&stream->active, true);

			}

fs/netfs/direct_write.c

+0 −1
Original line number Diff line number Diff line
@@ -111,7 +111,6 @@ static int netfs_unbuffered_write(struct netfs_io_request *wreq) 
			netfs_prepare_write(wreq, stream, wreq->start + wreq->transferred);

			subreq = stream->construct;

			stream->construct = NULL;

			stream->front = NULL;

		}



		/* Check if (re-)preparation failed. */

fs/netfs/read_collect.c

+2 −2
Original line number Diff line number Diff line
@@ -205,7 +205,8 @@ static void netfs_collect_read_results(struct netfs_io_request *rreq) 
	 * in progress.  The issuer thread may be adding stuff to the tail

	 * whilst we're doing this.

	 */

	front = READ_ONCE(stream->front);

	front = list_first_entry_or_null(&stream->subrequests,

					 struct netfs_io_subrequest, rreq_link);

	while (front) {

		size_t transferred;
@@ -301,7 +302,6 @@ static void netfs_collect_read_results(struct netfs_io_request *rreq) 
		list_del_init(&front->rreq_link);

		front = list_first_entry_or_null(&stream->subrequests,

						 struct netfs_io_subrequest, rreq_link);

		stream->front = front;

		spin_unlock(&rreq->lock);

		netfs_put_subrequest(remove,

				     notes & ABANDON_SREQ ?

fs/netfs/read_single.c

+0 −1
Original line number Diff line number Diff line
@@ -107,7 +107,6 @@ static int netfs_single_dispatch_read(struct netfs_io_request *rreq) 
	spin_lock(&rreq->lock);

	list_add_tail(&subreq->rreq_link, &stream->subrequests);

	trace_netfs_sreq(subreq, netfs_sreq_trace_added);

	stream->front = subreq;

	/* Store list pointers before active flag */

	smp_store_release(&stream->active, true);

	spin_unlock(&rreq->lock);