linux-kernel - [PATCH v2 10/51] dm: limit the max bio size as BIO_MAX_PAGES * PAGE

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Date:   Mon, 26 Jun 2017 20:09:53 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...com>, Christoph Hellwig <hch@...radead.org>,
        Huang Ying <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Ming Lei <ming.lei@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH v2 10/51] dm: limit the max bio size as BIO_MAX_PAGES * PAGE_SIZE

For BIO based DM, some targets aren't ready for dealing with
bigger incoming bio than 1Mbyte, such as crypt target.

Cc: Mike Snitzer <snitzer@...hat.com>
Cc:dm-devel@...hat.com
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 drivers/md/dm.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 96bd13e581cd..49583c623cdd 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -921,7 +921,16 @@ int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
 		return -EINVAL;
 	}
 
-	ti->max_io_len = (uint32_t) len;
+	/*
+	 * BIO based queue uses its own splitting. When multipage bvecs
+	 * is switched on, size of the incoming bio may be too big to
+	 * be handled in some targets, such as crypt.
+	 *
+	 * When these targets are ready for the big bio, we can remove
+	 * the limit.
+	 */
+	ti->max_io_len = min_t(uint32_t, len,
+			       (BIO_MAX_PAGES * PAGE_SIZE));
 
 	return 0;
 }
-- 
2.9.4