From 8cfd339b3d402f913fe520a4f35f30152fb4fb80 Mon Sep 17 00:00:00 2001 From: Thomas Huth Date: Tue, 14 Sep 2021 14:32:14 +0200 Subject: [PATCH 1/2] tools/virtiofsd: Add fstatfs64 syscall to the seccomp allowlist The virtiofsd currently crashes on s390x when doing something like this in the guest: mkdir -p /mnt/myfs mount -t virtiofs myfs /mnt/myfs touch /mnt/myfs/foo.txt stat -f /mnt/myfs/foo.txt The problem is that the fstatfs64 syscall is called in this case from the virtiofsd. We have to put it on the seccomp allowlist to avoid that the daemon gets killed in this case. Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2001728 Suggested-by: Vivek Goyal Signed-off-by: Thomas Huth Message-Id: <20210914123214.181885-1-thuth@redhat.com> Reviewed-by: Vivek Goyal Reviewed-by: Sergio Lopez Reviewed-by: Stefan Hajnoczi Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/passthrough_seccomp.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/virtiofsd/passthrough_seccomp.c b/tools/virtiofsd/passthrough_seccomp.c index f49ed94b5e..a3ce9f898d 100644 --- a/tools/virtiofsd/passthrough_seccomp.c +++ b/tools/virtiofsd/passthrough_seccomp.c @@ -51,6 +51,7 @@ static const int syscall_allowlist[] = { SCMP_SYS(fsetxattr), SCMP_SYS(fstat), SCMP_SYS(fstatfs), + SCMP_SYS(fstatfs64), SCMP_SYS(fsync), SCMP_SYS(ftruncate), SCMP_SYS(futex), From 046d91c83caac29e2ba26c63fd7d685a57463f6d Mon Sep 17 00:00:00 2001 From: Sergio Lopez Date: Tue, 24 Aug 2021 15:11:58 +0200 Subject: [PATCH 2/2] virtiofsd: Reverse req_list before processing it With the thread pool disabled, we add the requests in the queue to a GList, processing by iterating over there afterwards. For adding them, we're using "g_list_prepend()", which is more efficient but causes the requests to be processed in reverse order, breaking the read-ahead and request-merging optimizations in the host for sequential operations. According to the documentation, if you need to process the request in-order, using "g_list_prepend()" and then reversing the list with "g_list_reverse()" is more efficient than using "g_list_append()", so let's do it that way. Testing on a spinning disk (to boost the increase of read-ahead and request-merging) shows a 4x improvement on sequential write fio test: Test: fio --directory=/mnt/virtio-fs --filename=fio-file1 --runtime=20 --iodepth=16 --size=4G --direct=1 --blocksize=4K --ioengine libaio --rw write --name seqwrite-libaio Without "g_list_reverse()": ... Jobs: 1 (f=1): [W(1)][100.0%][w=22.4MiB/s][w=5735 IOPS][eta 00m:00s] seqwrite-libaio: (groupid=0, jobs=1): err= 0: pid=710: Tue Aug 24 12:58:16 2021 write: IOPS=5709, BW=22.3MiB/s (23.4MB/s)(446MiB/20002msec); 0 zone resets ... With "g_list_reverse()": ... Jobs: 1 (f=1): [W(1)][100.0%][w=84.0MiB/s][w=21.5k IOPS][eta 00m:00s] seqwrite-libaio: (groupid=0, jobs=1): err= 0: pid=716: Tue Aug 24 13:00:15 2021 write: IOPS=21.3k, BW=83.1MiB/s (87.2MB/s)(1663MiB/20001msec); 0 zone resets ... Signed-off-by: Sergio Lopez Message-Id: <20210824131158.39970-1-slp@redhat.com> Reviewed-by: Vivek Goyal Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/fuse_virtio.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c index fc2564a603..8f4fd165b9 100644 --- a/tools/virtiofsd/fuse_virtio.c +++ b/tools/virtiofsd/fuse_virtio.c @@ -716,6 +716,7 @@ static void *fv_queue_thread(void *opaque) /* Process all the requests. */ if (!se->thread_pool_size && req_list != NULL) { + req_list = g_list_reverse(req_list); g_list_foreach(req_list, fv_queue_worker, qi); g_list_free(req_list); req_list = NULL;