From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 17 Jan 2022 18:08:55 +0100 From: Greg Kurz Message-ID: <20220117180855.6353fc05@bahia> In-Reply-To: <20220113153249.710216-1-sebastian.hasler@stuvus.uni-stuttgart.de> References: <20220113153249.710216-1-sebastian.hasler@stuvus.uni-stuttgart.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Virtio-fs] [PATCH v2] virtiofsd: Do not support blocking flock List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Sebastian Hasler Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org On Thu, 13 Jan 2022 16:32:49 +0100 Sebastian Hasler wrote: > With the current implementation, blocking flock can lead to > deadlock. Thus, it's better to return EOPNOTSUPP if a user attempts > to perform a blocking flock request. > > Signed-off-by: Sebastian Hasler > --- Reviewed-by: Greg Kurz > tools/virtiofsd/passthrough_ll.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 64b5b4fbb1..faa62278c5 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -2442,6 +2442,15 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi, > int res; > (void)ino; > > + if (!(op & LOCK_NB)) { > + /* > + * Blocking flock can deadlock as there is only one thread > + * serving the queue. > + */ > + fuse_reply_err(req, EOPNOTSUPP); > + return; > + } > + > res = flock(lo_fi_fd(req, fi), op); > > fuse_reply_err(req, res == -1 ? errno : 0);