Re: [PATCH] md: don't account io stat for split bio

On Mon, May 10, 2021 at 9:39 PM Christoph Hellwig [off-list ref] wrote:

On Tue, May 11, 2021 at 10:13:41AM +0800, Guoqing Jiang wrote:

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Song and Artur, what are your opinion?

In the initial version of the io accounting patch the bio was cloned instead
of just overriding bi_end_io and bi_private. Would this be the right approach?

https://lore.kernel.org/linux-raid/20200601161256.27718-1-artur.paszkiewicz@intel.com/ (local)

Maybe we can have different approach for different personality layers.

1. raid1 and raid10 can do the accounting in their own layer since they
already
?????? clone bio here.
2. make the initial version handles other personality such as raid0 and
raid5
?????? in the md layer.

Also a sysfs node which can enable/disable the accounting could be helpful.

Yes.  Also if the original bi_end_io is restore before completing the
bio you can still override it.

Do you mean we can somehow avoid cloning the bio?

Thanks,
Song