From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57513) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y85s2-0002hP-7m for qemu-devel@nongnu.org; Mon, 05 Jan 2015 06:30:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y85ry-0001Bz-3i for qemu-devel@nongnu.org; Mon, 05 Jan 2015 06:30:50 -0500 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:41545 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y85rx-0001Bn-QH for qemu-devel@nongnu.org; Mon, 05 Jan 2015 06:30:46 -0500 From: Peter Lieven Date: Mon, 5 Jan 2015 12:29:49 +0100 Message-Id: <1420457389-16332-1-git-send-email-pl@kamp.de> Subject: [Qemu-devel] [PATCH] block: limited request size in write zeroes unsupported path List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, famz@redhat.com, Peter Lieven , mreitz@redhat.com, stefanha@redhat.com, den@openvz.org If bs->bl.max_write_zeroes is large and we end up in the unsupported path we might allocate a lot of memory for the iovector and/or even generate an oversized requests. Fix this by limiting the request by the minimum of the reported maximum transfer size or 16MB (32768 sectors). Reported-by: Denis V. Lunev Signed-off-by: Peter Lieven --- block.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index a612594..8009478 100644 --- a/block.c +++ b/block.c @@ -3203,6 +3203,9 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, if (ret == -ENOTSUP) { /* Fall back to bounce buffer if write zeroes is unsupported */ + int max_xfer_len = MIN_NON_ZERO(bs->bl.max_transfer_length, + MAX_WRITE_ZEROES_DEFAULT); + num = MIN(num, max_xfer_len); iov.iov_len = num * BDRV_SECTOR_SIZE; if (iov.iov_base == NULL) { iov.iov_base = qemu_try_blockalign(bs, num * BDRV_SECTOR_SIZE); @@ -3219,7 +3222,7 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs, /* Keep bounce buffer around if it is big enough for all * all future requests. */ - if (num < max_write_zeroes) { + if (num < max_xfer_len) { qemu_vfree(iov.iov_base); iov.iov_base = NULL; } -- 1.7.9.5