[PATCH] block: skip the split micro-optimization for devices with chunk size

From: Christoph Hellwig <hch@lst.de>
To: axboe@kernel.dk
Cc: linux-block@vger.kernel.org
Subject: [PATCH] block: skip the split micro-optimization for devices with chunk size
Date: Mon,  4 Nov 2019 16:06:17 -0800	[thread overview]
Message-ID: <20191105000617.26923-1-hch@lst.de> (raw)

If the devices sets a chunk size we might have to split I/O that is
smaller than a page size if it crosses the chunk boundary.  Skip the
micro-optimization for small I/Os in that case.

Fixes: b072e20f0084 ("block: merge invalidate_partitions into rescan_partitions")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-merge.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 06eb38357b41..f22cb6251d06 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -317,7 +317,8 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio,
 		 * are cloned, but compared to the performance impact of cloned
 		 * bios themselves the loop below doesn't matter anyway.
 		 */
-		if ((*bio)->bi_vcnt == 1 &&
+		if (!q->limits.chunk_sectors &&
+		    (*bio)->bi_vcnt == 1 &&
 		    (*bio)->bi_io_vec[0].bv_len <= PAGE_SIZE) {
 			*nr_segs = 1;
 			break;
-- 
2.20.1

