On Mon, Sep 28, 2020 at 11:29:41AM -0400, Mike Snitzer wrote:
> This backport applies (with mild offset) to both v5.4.67 and v5.8.11:
>
> >From ee1dfad5325ff1cfb2239e564cd411b3bfe8667a Mon Sep 17 00:00:00 2001
> From: Mike Snitzer <snitzer@xxxxxxxxxx>
> Date: Mon, 14 Sep 2020 13:04:19 -0400
> Subject: [PATCH] dm: fix bio splitting and its bio completion order for regular IO
>
> dm_queue_split() is removed because __split_and_process_bio() _must_
> handle splitting bios to ensure proper bio submission and completion
> ordering as a bio is split.
>
> Otherwise, multiple recursive calls to ->submit_bio will cause multiple
> split bios to be allocated from the same ->bio_split mempool at the same
> time. This would result in deadlock in low memory conditions because no
> progress could be made (only one bio is available in ->bio_split
> mempool).
>
> This fix has been verified to still fix the loss of performance, due
> to excess splitting, that commit 120c9257f5f1 provided.
>
> Fixes: 120c9257f5f1 ("Revert "dm: always call blk_queue_split() in dm_process_bio()"")
> Cc: stable@xxxxxxxxxxxxxxx # 5.0+, requires custom backport due to 5.9 changes
> Reported-by: Ming Lei <ming.lei@xxxxxxxxxx>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
What is the git id of this patch in Linus's tree?
thanks,
greg k-h
