FAILED: patch "[PATCH] dm raid: fix discard limits for raid1 and raid10" failed to apply to 5.9-stable tree

The patch below does not apply to the 5.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e0910c8e4f87bb9f767e61a778b0d9271c4dc512 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <[email protected]>
Date: Thu, 24 Sep 2020 13:14:52 -0400
Subject: [PATCH] dm raid: fix discard limits for raid1 and raid10

Block core warned that discard_granularity was 0 for dm-raid with personality of raid1. Reason is that raid_io_hints() was incorrectly special-casing raid1 rather than raid0.

But since commit 29efc390b9462 ("md/md0: optimize raid0 discard handling") even raid0 properly handles large discards.

Fix raid_io_hints() by removing discard limits settings for raid1. Also, fix limits for raid10 by properly stacking underlying limits as done in blk_stack_limits().

Depends-on: 29efc390b9462 ("md/md0: optimize raid0 discard handling")

index 56b723d012ac..dc8568ab96f2 100644
@@ -3730,12 +3730,14 @@ static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits)
 	blk_limits_io_opt(limits, chunk_size_bytes * mddev_data_stripes(rs));
 
 	/*
-	 * RAID1 and RAID10 personalities require bio splitting,
-	 * RAID0/4/5/6 don't and process large discard bios properly.
+	 * RAID10 personality requires bio splitting,
+	 * RAID0/1/4/5/6 don't and process large discard bios properly.
 	 */
-	if (rs_is_raid1(rs) || rs_is_raid10(rs)) {
-		limits->discard_granularity = chunk_size_bytes;
-		limits->max_discard_sectors = rs->md.chunk_sectors;
+	if (rs_is_raid10(rs)) {
+		limits->discard_granularity = max(chunk_size_bytes,
+						  limits->discard_granularity);
+		limits->max_discard_sectors = min_not_zero(rs->md.chunk_sectors,
+							   limits->max_discard_sectors);
 	}
 }