Thread (104 messages) 104 messages, 13 authors, 2023-12-05

Re: [PATCH 21/21] nvme: Support atomic writes

From: John Garry <john.g.garry@oracle.com>
Date: 2023-11-10 08:45:18
Also in: linux-block, linux-fsdevel, linux-nvme, linux-xfs, lkml

On 10/11/2023 06:29, Christoph Hellwig wrote:
Yes.
quoted
As for splitting, it is not permitted for atomic writes and only a single
bio is permitted to be created per write. Are more integrity checks
required?
I'm more worried about the problem where we accidentally add a split.
The whole bio merge/split path is convoluted and we had plenty of
bugs in the past by not looking at all the correct flags or opcodes.
Yes, this is always a concern.

Some thoughts on things which could be done:
- For no merging, ensure request length is a power-of-2 when enqueuing 
to block driver. This is simple but not watertight.
- Create a per-bio checksum when the bio is created for the atomic write 
and ensure integrity when queuing to the block driver
- a new block layer datapath which ensures no merging or splitting, but 
this seems a bit OTT

BTW, on topic of splitting, that NVMe virt boundary is a pain and I hope 
that we could ignore/avoid it for atomic writes.

Thanks,
John
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help