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[PATCH v1 0/1] virtio-block: switch to blk_get_max_hw_transfer
From: |
Or Ozeri |
Subject: |
[PATCH v1 0/1] virtio-block: switch to blk_get_max_hw_transfer |
Date: |
Thu, 9 Dec 2021 03:28:14 -0600 |
Since moving to qemu 6.1.0 we've been seeing disk failures inside a qemu guest
VM.
This happened when using if=virtio on a host /dev/nbdX device.
Binary searching on qemu commit history, I found these errors start on this
commit:
Commit 18473467
file-posix: try BLKSECTGET on block devices too, do not round to power of 2
The above commit switched posix block device limits (including host /dev/nbdX
devices)
to query limits from /sys/dev/block/..., instead of using predefined limits.
The scsi-generic driver was changed to use the queried limits,
whereas the virtio-blk driver was only the queried max_iov,
but still using the predefined max_transfer, which is unlimited in qemu.
For NBD devices, max_iov is unlimited by the kernel nbd driver.
As as consequence, the virtio-blk merged requests over the limit of our host
/dev/nbdX device,
which apparently caused the guest disk errors.
The solution that worked for me was to change the virtio-blk driver to use the
max_transfer
limit queried from the posix host device (given by blk_get_max_hw_transfer).
Or Ozeri (1):
virtio-block: switch to blk_get_max_hw_transfer
hw/block/virtio-blk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--
2.25.1
- [PATCH v1 0/1] virtio-block: switch to blk_get_max_hw_transfer,
Or Ozeri <=