FAILED: patch "[PATCH] dm: do not allow readahead to limit IO size" failed to apply to 4.19-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.19-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 <stable@vger.kernel.org>.

thanks,

greg k-h

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

From c6d6e9b0f6b4201c77f2cea3964dd122697e3543 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Tue, 18 Dec 2018 09:25:37 -0800
Subject: [PATCH] dm: do not allow readahead to limit IO size

Update DM to set the bdi's io_pages.  This fixes reads to be capped at
the device's max request size (even if user's read IO exceeds the
established readahead setting).

Fixes: 9491ae4a ("mm: don't cap request size based on read-ahead setting")
Cc: stable@vger.kernel.org
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 844f7d0f2ef8..4b1be754cc41 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1927,6 +1927,9 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	 */
 	if (blk_queue_is_zoned(q))
 		blk_revalidate_disk_zones(t->md->disk);
+
+	/* Allow reads to exceed readahead limits */
+	q->backing_dev_info->io_pages = limits->max_sectors >> (PAGE_SHIFT - 9);
 }
 
 unsigned int dm_table_get_num_targets(struct dm_table *t)