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@redhat.com 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@vger.kernel.org # 5.0+, requires custom backport due to 5.9 changes Reported-by: Ming Lei ming.lei@redhat.com Signed-off-by: Mike Snitzer snitzer@redhat.com
What is the git id of this patch in Linus's tree?
thanks,
greg k-h