async_pmem_flush() allocates a child bio for the flush with GFP_ATOMIC.
This runs from pmem_submit_bio(), a ->submit_bio callback that executes
in a sleepable context, so there is no atomicity requirement here.
bio_alloc() only guarantees success when __GFP_DIRECT_RECLAIM is set,
because that is what lets it fall back to the mempool reserve. With
GFP_ATOMIC the reclaim bit is absent, so the allocation can fail and
return -ENOMEM whenever the fast paths (percpu cache and slab) are
exhausted, which is common right after boot. A flush is issued from
filesystem writeback and must not fail on a transient allocation
shortage, otherwise the device can appear unmountable:
Buffer I/O error on dev pmem0, logical block 0, lost sync page write
Switch to GFP_NOIO so __GFP_DIRECT_RECLAIM is set and the allocation can
make forward progress. However, bio_alloc() draws from the shared
fs_bio_set, and the incoming bio being flushed may itself have come from
fs_bio_set; allocating a second bio from the same set while submitting
underneath ->submit_bio can deadlock the mempool. Add a driver-private
bio_set for the flush and allocate from it via bio_alloc_bioset(), so
the flush bio has an independent reserve.
With a dedicated mempool-backed bio_set and GFP_NOIO the allocation
cannot fail, so drop the now-redundant NULL check.
Fixes: 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
Suggested-by: Christoph Hellwig <[email protected]>
Signed-off-by: Joseph Qi <[email protected]>
---
drivers/nvdimm/nd_virtio.c | 11 ++++++-----
drivers/nvdimm/virtio_pmem.c | 11 ++++++++++-
drivers/nvdimm/virtio_pmem.h | 4 ++++
3 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
index 4176046627beb..b4bd21edf5c1c 100644
--- a/drivers/nvdimm/nd_virtio.c
+++ b/drivers/nvdimm/nd_virtio.c
@@ -110,17 +110,18 @@ static int virtio_pmem_flush(struct nd_region *nd_region)
/* The asynchronous flush callback function */
int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)
{
+ struct virtio_device *vdev = nd_region->provider_data;
+ struct virtio_pmem *vpmem = vdev->priv;
+
/*
* Create child bio for asynchronous flush and chain with
* parent bio. Otherwise directly call nd_region flush.
*/
if (bio && bio->bi_iter.bi_sector != -1) {
- struct bio *child = bio_alloc(bio->bi_bdev, 0,
- REQ_OP_WRITE | REQ_PREFLUSH,
- GFP_ATOMIC);
+ struct bio *child = bio_alloc_bioset(bio->bi_bdev, 0,
+ REQ_OP_WRITE | REQ_PREFLUSH, GFP_NOIO,
+ &vpmem->flush_bio_set);
- if (!child)
- return -ENOMEM;
bio_clone_blkg_association(child, bio);
child->bi_iter.bi_sector = -1;
bio_chain(child, bio);
diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
index 77b1966619059..136179506b478 100644
--- a/drivers/nvdimm/virtio_pmem.c
+++ b/drivers/nvdimm/virtio_pmem.c
@@ -65,12 +65,17 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
}
mutex_init(&vpmem->flush_lock);
+ err = bioset_init(&vpmem->flush_bio_set, BIO_POOL_SIZE, 0, 0);
+ if (err) {
+ dev_err(&vdev->dev, "failed to initialize flush bio_set\n");
+ goto out_err;
+ }
vpmem->vdev = vdev;
vdev->priv = vpmem;
err = init_vq(vpmem);
if (err) {
dev_err(&vdev->dev, "failed to initialize virtio pmem vq's\n");
- goto out_err;
+ goto out_bioset;
}
if (virtio_has_feature(vdev, VIRTIO_PMEM_F_SHMEM_REGION)) {
@@ -131,6 +136,8 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
nvdimm_bus_unregister(vpmem->nvdimm_bus);
out_vq:
vdev->config->del_vqs(vdev);
+out_bioset:
+ bioset_exit(&vpmem->flush_bio_set);
out_err:
return err;
}
@@ -138,10 +145,12 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
static void virtio_pmem_remove(struct virtio_device *vdev)
{
struct nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev);
+ struct virtio_pmem *vpmem = vdev->priv;
nvdimm_bus_unregister(nvdimm_bus);
vdev->config->del_vqs(vdev);
virtio_reset_device(vdev);
+ bioset_exit(&vpmem->flush_bio_set);
}
static int virtio_pmem_freeze(struct virtio_device *vdev)
diff --git a/drivers/nvdimm/virtio_pmem.h b/drivers/nvdimm/virtio_pmem.h
index f72cf17f9518f..4ff2076f75047 100644
--- a/drivers/nvdimm/virtio_pmem.h
+++ b/drivers/nvdimm/virtio_pmem.h
@@ -15,6 +15,7 @@
#include <linux/libnvdimm.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
+#include <linux/bio.h>
struct virtio_pmem_request {
struct virtio_pmem_req req;
@@ -39,6 +40,9 @@ struct virtio_pmem {
/* Serialize flush requests to the device. */
struct mutex flush_lock;
+ /* bio_set for allocating flush child bios */
+ struct bio_set flush_bio_set;
+
/* nvdimm bus registers virtio pmem device */
struct nvdimm_bus *nvdimm_bus;
struct nvdimm_bus_descriptor nd_desc;
--
2.39.3
