From: Hou Tao <houtao1@xxxxxxxxxx>
The following warning was reported when doing fsync on a pmem device:
------------[ cut here ]------------
WARNING: CPU: 2 PID: 384 at block/blk-core.c:751 submit_bio_noacct+0x340/0x520
Modules linked in:
CPU: 2 PID: 384 Comm: mkfs.xfs Not tainted 6.4.0-rc7+ #154
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
RIP: 0010:submit_bio_noacct+0x340/0x520
......
Call Trace:
<TASK>
? asm_exc_invalid_op+0x1b/0x20
? submit_bio_noacct+0x340/0x520
? submit_bio_noacct+0xd5/0x520
submit_bio+0x37/0x60
async_pmem_flush+0x79/0xa0
nvdimm_flush+0x17/0x40
pmem_submit_bio+0x370/0x390
__submit_bio+0xbc/0x190
submit_bio_noacct_nocheck+0x14d/0x370
submit_bio_noacct+0x1ef/0x520
submit_bio+0x55/0x60
submit_bio_wait+0x5a/0xc0
blkdev_issue_flush+0x44/0x60
The root cause is that submit_bio_noacct() needs bio_op() is either
WRITE or ZONE_APPEND for flush bio and async_pmem_flush() doesn't assign
REQ_OP_WRITE when allocating flush bio.
The reason for allocating a new flush bio is to execute the flush
command asynchrously and doesn't want to block the original submit_bio()
invocation. However the original submit_bio() will be blocked anyway,
because the nested submit_bio() for the flush bio just places the flush
bio in current->bio_list and the original submit_bio() only returns
after submitting all bio in bio_list.
So just removing the allocation of new flush bio and do synchronous
flush directly.
Fixes: b4a6bb3a67aa ("block: add a sanity check for non-write flush/fua bios")
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
Hi Jens & Dan,
I found Pankaj was working on the optimization of virtio-pmem flush bio
[0], but considering the last status update was 1/12/2022, so could you
please pick the patch up for v6.7 and we can do the flush optimization
later ?
[0]: https://lore.kernel.org/lkml/20220111161937.56272-1-pankaj.gupta.linux@xxxxxxxxx/T/
drivers/nvdimm/nd_virtio.c | 16 ----------------
1 file changed, 16 deletions(-)
diff --git a/drivers/nvdimm/nd_virtio.c b/drivers/nvdimm/nd_virtio.c
index c6a648fd8744..a7d510f446e0 100644
--- a/drivers/nvdimm/nd_virtio.c
+++ b/drivers/nvdimm/nd_virtio.c
@@ -100,22 +100,6 @@ 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)
{
- /*
- * 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_PREFLUSH,
- GFP_ATOMIC);
-
- if (!child)
- return -ENOMEM;
- bio_clone_blkg_association(child, bio);
- child->bi_iter.bi_sector = -1;
- bio_chain(child, bio);
- submit_bio(child);
- return 0;
- }
if (virtio_pmem_flush(nd_region))
return -EIO;
--
2.29.2
