Li Chen wrote: > Under heavy concurrent flush traffic, virtio-pmem can overflow its request > virtqueue (req_vq): virtqueue_add_sgs() starts returning -ENOSPC and the > driver logs "no free slots in the virtqueue". Shortly after that the > device enters VIRTIO_CONFIG_S_NEEDS_RESET and flush requests fail with > "virtio pmem device needs a reset". > > Serialize virtio_pmem_flush() with a per-device mutex so only one flush > request is in-flight at a time. This prevents req_vq descriptor overflow > under high concurrency. > > Reproducer (guest with virtio-pmem): > - mkfs.ext4 -F /dev/pmem0 > - mount -t ext4 -o dax,noatime /dev/pmem0 /mnt/bench > - fio: ioengine=io_uring rw=randwrite bs=4k iodepth=64 numjobs=64 > direct=1 fsync=1 runtime=30s time_based=1
I don't see this error. <file> 13:28:50 > cat foo.fio # test http://lore.kernel.org/[email protected] [global] filename=/mnt/bench/foo ioengine=io_uring size=1G bs=4K iodepth=64 numjobs=64 direct=1 fsync=1 runtime=30s time_based=1 [rand-write] rw=randwrite </file> It's possible I'm doing something wrong. Can you share your qemu cmdline or more details on the bug yall see. > - dmesg: "no free slots in the virtqueue" > "virtio pmem device needs a reset" > > Fixes: 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver") > Signed-off-by: Li Chen <[email protected]> > --- > drivers/nvdimm/nd_virtio.c | 15 +++++++++++---- > drivers/nvdimm/virtio_pmem.c | 1 + > drivers/nvdimm/virtio_pmem.h | 4 ++++ > 3 files changed, 16 insertions(+), 4 deletions(-) > > diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c > index c3f07be4aa22..827a17fe7c71 100644 > --- a/drivers/nvdimm/nd_virtio.c > +++ b/drivers/nvdimm/nd_virtio.c > @@ -44,19 +44,24 @@ static int virtio_pmem_flush(struct nd_region *nd_region) > unsigned long flags; > int err, err1; > > + might_sleep(); > + mutex_lock(&vpmem->flush_lock); Assuming this does fix a bug I'd rather use guard here. guard(mutex)(&vpmem->flush_lock); Then skip all the gotos and out_unlock stuff. Also, does this affect performance at all? Ira > + > /* > * Don't bother to submit the request to the device if the device is > * not activated. > */ > if (vdev->config->get_status(vdev) & VIRTIO_CONFIG_S_NEEDS_RESET) { > dev_info(&vdev->dev, "virtio pmem device needs a reset\n"); > - return -EIO; > + err = -EIO; > + goto out_unlock; > } > > - might_sleep(); > req_data = kmalloc(sizeof(*req_data), GFP_KERNEL); > - if (!req_data) > - return -ENOMEM; > + if (!req_data) { > + err = -ENOMEM; > + goto out_unlock; > + } > > req_data->done = false; > init_waitqueue_head(&req_data->host_acked); > @@ -103,6 +108,8 @@ static int virtio_pmem_flush(struct nd_region *nd_region) > } > > kfree(req_data); > +out_unlock: > + mutex_unlock(&vpmem->flush_lock); > return err; > }; [snip]
