linux-kernel - [PATCH 4.20 28/65] dm: do not allow readahead to limit IO size

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Date:   Fri, 11 Jan 2019 15:15:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.20 28/65] dm: do not allow readahead to limit IO size

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jaegeuk Kim <jaegeuk@...nel.org>

commit c6d6e9b0f6b4201c77f2cea3964dd122697e3543 upstream.

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@...r.kernel.org
Reviewed-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-table.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1927,6 +1927,9 @@ void dm_table_set_restrictions(struct dm
 	 */
 	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)