From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39550) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b2b6a-0005h3-74 for qemu-devel@nongnu.org; Tue, 17 May 2016 05:16:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b2b6U-0007LI-5t for qemu-devel@nongnu.org; Tue, 17 May 2016 05:15:55 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:9001 helo=relay.sw.ru) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b2b6T-0007Km-OL for qemu-devel@nongnu.org; Tue, 17 May 2016 05:15:50 -0400 From: "Denis V. Lunev" Date: Tue, 17 May 2016 12:15:39 +0300 Message-Id: <1463476543-3087-2-git-send-email-den@openvz.org> In-Reply-To: <1463476543-3087-1-git-send-email-den@openvz.org> References: <1463476543-3087-1-git-send-email-den@openvz.org> Subject: [Qemu-devel] [PATCH 1/5] block: split write_zeroes always List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: den@openvz.org, Eric Blake , Kevin Wolf We should split requests even if they are less than write_zeroes_alignment. For example we can have the following request: offset 62k size 4k write_zeroes_alignment 64k The original code sent 1 request covering 2 qcow2 clusters, and resulted in both clusters being allocated. But by splitting the request, we can cater to the case where one of the two clusters can be zeroed as a whole, for only 1 cluster allocated after the operation. Signed-off-by: Denis V. Lunev CC: Eric Blake CC: Kevin Wolf --- block/io.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/block/io.c b/block/io.c index cd6d71a..6a24ea8 100644 --- a/block/io.c +++ b/block/io.c @@ -1172,13 +1172,13 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, /* Align request. Block drivers can expect the "bulk" of the request * to be aligned. */ - if (bs->bl.write_zeroes_alignment - && num > bs->bl.write_zeroes_alignment) { + if (bs->bl.write_zeroes_alignment) { if (sector_num % bs->bl.write_zeroes_alignment != 0) { /* Make a small request up to the first aligned sector. */ num = bs->bl.write_zeroes_alignment; num -= sector_num % bs->bl.write_zeroes_alignment; - } else if ((sector_num + num) % bs->bl.write_zeroes_alignment != 0) { + } else if (num > bs->bl.write_zeroes_alignment && + (sector_num + num) % bs->bl.write_zeroes_alignment != 0) { /* Shorten the request to the last aligned sector. num cannot * underflow because num > bs->bl.write_zeroes_alignment. */ -- 2.1.4