async_pmem_flush() can allocate a child flush bio from filesystem flush and writeback paths. GFP_ATOMIC is unnecessarily restrictive there and can make the allocation fail under pressure, which then propagates -ENOMEM to the flush caller.
A local virtio-pmem mkfs sanity test hit a flush failure before this change: wipefs: /dev/pmem0: cannot flush modified buffers: Input/output error mkfs.ext4: Input/output error while writing out and closing file system nd_region region0: dbg: nvdimm_flush rc=-5 The debug log showed async_pmem_flush() was entered and nvdimm_flush() returned -EIO. With GFP_NOIO, the same test reached mkfs_rc=0, mount_rc=0, and umount_rc=0. Use GFP_NOIO instead. The path may sleep, but it must not recurse into filesystem I/O reclaim while it is already servicing a flush request. Signed-off-by: Li Chen <[email protected]> --- v3->v4: - New patch. 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; -- 2.52.0
