From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60553) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bNjzE-0001R4-Ql for qemu-devel@nongnu.org; Thu, 14 Jul 2016 12:59:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bNjzB-0001vH-LS for qemu-devel@nongnu.org; Thu, 14 Jul 2016 12:59:44 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:11431 helo=relay.sw.ru) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bNjzB-0001ux-8W for qemu-devel@nongnu.org; Thu, 14 Jul 2016 12:59:41 -0400 From: Vladimir Sementsov-Ogievskiy Date: Thu, 14 Jul 2016 19:59:25 +0300 Message-Id: <1468515565-81313-1-git-send-email-vsementsov@virtuozzo.com> Subject: [Qemu-devel] [PATCH v2] qcow2: do not allocate extra memory List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: mreitz@redhat.com, kwolf@redhat.com, stefanha@redhat.com, eblake@redhat.com, den@openvz.org, Vladimir Sementsov-Ogievskiy There are no needs to allocate more than one cluster, as we set avail_out for deflate to one cluster. Zlib docs (http://www.zlib.net/manual.html) says: "deflate compresses as much data as possible, and stops when the input buffer becomes empty or the output buffer becomes full." So, deflate will not write more than avail_out to output buffer. If there is no enough space in output buffer for compressed data (it may be larger than input data) deflate just returns Z_OK. (if all data is compressed and written to output buffer deflate returns Z_STREAM_END). Signed-off-by: Vladimir Sementsov-Ogievskiy --- v2: improve commit message block/qcow.c | 2 +- block/qcow2.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/block/qcow.c b/block/qcow.c index ac849bd..d8826f3 100644 --- a/block/qcow.c +++ b/block/qcow.c @@ -983,7 +983,7 @@ static int qcow_write_compressed(BlockDriverState *bs, int64_t sector_num, return ret; } - out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); + out_buf = g_malloc(s->cluster_size); /* best compression, small window, no zlib header */ memset(&strm, 0, sizeof(strm)); diff --git a/block/qcow2.c b/block/qcow2.c index a5ea19b..b1c90ae 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2612,7 +2612,7 @@ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num, return ret; } - out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128); + out_buf = g_malloc(s->cluster_size); /* best compression, small window, no zlib header */ memset(&strm, 0, sizeof(strm)); -- 1.8.3.1