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
Use GFP_NOIO instead. It keeps __GFP_DIRECT_RECLAIM so the mempool and
rescuer machinery guarantee forward progress, while avoiding recursion
back into the filesystem and block layer during writeback.
Fixes: 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
Signed-off-by: Joseph Qi <[email protected]>
---
drivers/nvdimm/nd_virtio.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
index 4176046627beb..081370aac6317 100644
--- a/drivers/nvdimm/nd_virtio.c
+++ b/drivers/nvdimm/nd_virtio.c
@@ -117,7 +117,7 @@ int async_pmem_flush(struct nd_region *nd_region, struct
bio *bio)
if (bio && bio->bi_iter.bi_sector != -1) {
struct bio *child = bio_alloc(bio->bi_bdev, 0,
REQ_OP_WRITE | REQ_PREFLUSH,
- GFP_ATOMIC);
+ GFP_NOIO);
if (!child)
return -ENOMEM;
--
2.39.3
