linux-kernel - [PATCH v3 15/15] md/raid5: Increase restriction on max segments per request

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Date:   Thu, 16 Jun 2022 13:19:45 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        Song Liu <song@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Guoqing Jiang <guoqing.jiang@...ux.dev>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <Martin.Oliveira@...eticom.com>,
        David Sloan <David.Sloan@...eticom.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v3 15/15] md/raid5: Increase restriction on max segments per request

The block layer defaults the maximum segments to 128, which means
requests tend to get split around the 512KB depending on how many
pages can be merged. There's no such restriction in the raid5 code
so increase the limit to USHRT_MAX so that larger requests can be
sent as one.

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
---
 drivers/md/raid5.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e48c16bfe657..5723a497108a 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -8005,6 +8005,9 @@ static int raid5_run(struct mddev *mddev)
 		 */
 		blk_queue_max_hw_sectors(mddev->queue,
 			RAID5_MAX_REQ_STRIPES << RAID5_STRIPE_SHIFT(conf));
+
+		/* No restrictions on the number of segments in the request */
+		blk_queue_max_segments(mddev->queue, USHRT_MAX);
 	}
 
 	if (log_init(conf, journal_dev, raid5_has_ppl(conf)))
-- 
2.30.2