diff options
| author | Li Chen <me@linux.beauty> | 2026-02-03 10:13:51 +0800 |
|---|---|---|
| committer | Ira Weiny <ira.weiny@intel.com> | 2026-02-04 13:16:40 -0600 |
| commit | a9ba6733c7f1096c4506bf4e34a546e07242df74 (patch) | |
| tree | 9d7500cd61654a2fa187d8f540e150561c10d078 | |
| parent | 9c0fc1d37f531fd33abc9b3a009b818ff1bddc22 (diff) | |
nvdimm: virtio_pmem: serialize flush requests
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
- 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 <me@linux.beauty>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20260203021353.121091-1-me@linux.beauty
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
| -rw-r--r-- | drivers/nvdimm/nd_virtio.c | 3 | ||||
| -rw-r--r-- | drivers/nvdimm/virtio_pmem.c | 1 | ||||
| -rw-r--r-- | drivers/nvdimm/virtio_pmem.h | 4 |
3 files changed, 7 insertions, 1 deletions
diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c index c3f07be4aa22..af82385be7c6 100644 --- a/drivers/nvdimm/nd_virtio.c +++ b/drivers/nvdimm/nd_virtio.c @@ -44,6 +44,8 @@ static int virtio_pmem_flush(struct nd_region *nd_region) unsigned long flags; int err, err1; + guard(mutex)(&vpmem->flush_lock); + /* * Don't bother to submit the request to the device if the device is * not activated. @@ -53,7 +55,6 @@ static int virtio_pmem_flush(struct nd_region *nd_region) return -EIO; } - might_sleep(); req_data = kmalloc(sizeof(*req_data), GFP_KERNEL); if (!req_data) return -ENOMEM; diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c index 2396d19ce549..77b196661905 100644 --- a/drivers/nvdimm/virtio_pmem.c +++ b/drivers/nvdimm/virtio_pmem.c @@ -64,6 +64,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev) goto out_err; } + mutex_init(&vpmem->flush_lock); vpmem->vdev = vdev; vdev->priv = vpmem; err = init_vq(vpmem); diff --git a/drivers/nvdimm/virtio_pmem.h b/drivers/nvdimm/virtio_pmem.h index 0dddefe594c4..f72cf17f9518 100644 --- a/drivers/nvdimm/virtio_pmem.h +++ b/drivers/nvdimm/virtio_pmem.h @@ -13,6 +13,7 @@ #include <linux/module.h> #include <uapi/linux/virtio_pmem.h> #include <linux/libnvdimm.h> +#include <linux/mutex.h> #include <linux/spinlock.h> struct virtio_pmem_request { @@ -35,6 +36,9 @@ struct virtio_pmem { /* Virtio pmem request queue */ struct virtqueue *req_vq; + /* Serialize flush requests to the device. */ + struct mutex flush_lock; + /* nvdimm bus registers virtio pmem device */ struct nvdimm_bus *nvdimm_bus; struct nvdimm_bus_descriptor nd_desc; |