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Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: Steve French cc: dhowells@redhat.com, Paulo Alcantara , linux-cifs@vger.kernel.org, netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] netfs: Fix hang due to missing case in final DIO read result collection Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-ID: <583791.1750073757.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Mon, 16 Jun 2025 12:35:57 +0100 Message-ID: <583792.1750073757@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" When doing a DIO read, if the subrequests we issue fail and cause the request PAUSE flag to be set to put a pause on subrequest generation, we may complete collection of the subrequests (possibly discarding them) prior to the ALL_QUEUED flags being set. In such a case, netfs_read_collection() doesn't see ALL_QUEUED being set after netfs_collect_read_results() returns and will just return to the app (the collector can be seen unpausing the generator in the trace log). The subrequest generator can then set ALL_QUEUED and the app thread reaches netfs_wait_for_request(). This causes netfs_collect_in_app() to be called to see if we're done yet, but there's missing case here. netfs_collect_in_app() will see that a thread is active and set inactive to false, but won't see any subrequests in the read stream, and so won't set need_collect to true. The function will then just return 0, indicating that the caller should just sleep until further activity (which won't be forthcoming) occurs. Fix this by making netfs_collect_in_app() check to see if an active thread is complete - i.e. that ALL_QUEUED is set and the subrequests list is empty - and to skip the sleep return path. The collector will then be called which will clear the request IN_PROGRESS flag, allowing the app to progress. Fixes: 2b1424cd131c ("netfs: Fix wait/wake to be consistent about the waitq= ueue used") Reported-by: Steve French Signed-off-by: David Howells cc: Paulo Alcantara cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org --- diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c index 43b67a28a8fa..1966dfba285e 100644 --- a/fs/netfs/misc.c +++ b/fs/netfs/misc.c @@ -381,7 +381,7 @@ void netfs_wait_for_in_progress_stream(struct netfs_io_= request *rreq, static int netfs_collect_in_app(struct netfs_io_request *rreq, bool (*collector)(struct netfs_io_request *rreq)) { - bool need_collect =3D false, inactive =3D true; + bool need_collect =3D false, inactive =3D true, done =3D true; =20 for (int i =3D 0; i < NR_IO_STREAMS; i++) { struct netfs_io_subrequest *subreq; @@ -400,9 +400,11 @@ static int netfs_collect_in_app(struct netfs_io_reques= t *rreq, need_collect =3D true; break; } + if (subreq || test_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags)) + done =3D false; } =20 - if (!need_collect && !inactive) + if (!need_collect && !inactive && !done) return 0; /* Sleep */ =20 __set_current_state(TASK_RUNNING);