linux-kernel - [PATCH 16/18] block: use memcpy_from_bvec in __blk_queue

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Message-Id: <20210615132456.753241-17-hch@lst.de>
Date:   Tue, 15 Jun 2021 15:24:54 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jens Axboe <axboe@...nel.dk>, Thomas Gleixner <tglx@...utronix.de>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Geoff Levand <geoff@...radead.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Dongsheng Yang <dongsheng.yang@...ystack.cn>,
        Mike Snitzer <snitzer@...hat.com>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Ira Weiny <ira.weiny@...el.com>, dm-devel@...hat.com,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        ceph-devel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: [PATCH 16/18] block: use memcpy_from_bvec in __blk_queue_bounce

Rewrite the actual bounce buffering loop in __blk_queue_bounce to that
the memcpy_to_bvec helper can be used to perform the data copies.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 block/bounce.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/block/bounce.c b/block/bounce.c
index 7e9e666c04dc..05fc7148489d 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -239,24 +239,19 @@ void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
 	 * because the 'bio' is single-page bvec.
 	 */
 	for (i = 0, to = bio->bi_io_vec; i < bio->bi_vcnt; to++, i++) {
-		struct page *page = to->bv_page;
+		struct page *bounce_page;
 
-		if (!PageHighMem(page))
+		if (!PageHighMem(to->bv_page))
 			continue;
 
-		to->bv_page = mempool_alloc(&page_pool, GFP_NOIO);
-		inc_zone_page_state(to->bv_page, NR_BOUNCE);
+		bounce_page = mempool_alloc(&page_pool, GFP_NOIO);
+		inc_zone_page_state(bounce_page, NR_BOUNCE);
 
 		if (rw == WRITE) {
-			char *vto, *vfrom;
-
-			flush_dcache_page(page);
-
-			vto = page_address(to->bv_page) + to->bv_offset;
-			vfrom = kmap_atomic(page) + to->bv_offset;
-			memcpy(vto, vfrom, to->bv_len);
-			kunmap_atomic(vfrom);
+			flush_dcache_page(to->bv_page);
+			memcpy_from_bvec(page_address(bounce_page), to);
 		}
+		to->bv_page = bounce_page;
 	}
 
 	trace_block_bio_bounce(*bio_orig);
-- 
2.30.2