From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40720) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y86rU-0007yt-Gn for qemu-devel@nongnu.org; Mon, 05 Jan 2015 07:34:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y86rQ-0005yd-3J for qemu-devel@nongnu.org; Mon, 05 Jan 2015 07:34:20 -0500 Received: from relay.parallels.com ([195.214.232.42]:57909) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y86rP-0005yS-SU for qemu-devel@nongnu.org; Mon, 05 Jan 2015 07:34:16 -0500 Message-ID: <54AA84BF.2010808@parallels.com> Date: Mon, 5 Jan 2015 15:34:07 +0300 From: "Denis V. Lunev" MIME-Version: 1.0 References: <1420457389-16332-1-git-send-email-pl@kamp.de> In-Reply-To: <1420457389-16332-1-git-send-email-pl@kamp.de> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [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: Peter Lieven , qemu-devel@nongnu.org Cc: kwolf@redhat.com, den@openvz.org, famz@redhat.com, stefanha@redhat.com, mreitz@redhat.com On 05/01/15 14:29, Peter Lieven wrote: > 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; > } > Reviewed-by: Denis V. Lunev Though pls consider my patch v3, it avoids allocation of 16 Mb here and uses only 1 Mb of memory.