From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55400) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YG9xt-0008IZ-B5 for qemu-devel@nongnu.org; Tue, 27 Jan 2015 12:30:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YG9xs-0003YB-C3 for qemu-devel@nongnu.org; Tue, 27 Jan 2015 12:30:13 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56196) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YG9xs-0003Y5-5q for qemu-devel@nongnu.org; Tue, 27 Jan 2015 12:30:12 -0500 Message-ID: <54C7CB19.4010904@redhat.com> Date: Tue, 27 Jan 2015 12:30:01 -0500 From: Max Reitz MIME-Version: 1.0 References: <1422366699-17473-1-git-send-email-den@openvz.org> <1422366699-17473-5-git-send-email-den@openvz.org> In-Reply-To: <1422366699-17473-5-git-send-email-den@openvz.org> Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/7] block: use fallocate(FALLOC_FL_ZERO_RANGE) in handle_aiocb_write_zeroes List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Denis V. Lunev" Cc: Kevin Wolf , Peter Lieven , Fam Zheng , qemu-devel@nongnu.org, Stefan Hajnoczi On 2015-01-27 at 08:51, Denis V. Lunev wrote: > This efficiently writes zeroes on Linux if the kernel is capable enough. > FALLOC_FL_ZERO_RANGE correctly handles all cases, including and not > including file expansion. > > Signed-off-by: Denis V. Lunev > CC: Kevin Wolf > CC: Stefan Hajnoczi > CC: Peter Lieven > CC: Fam Zheng > --- > block/raw-posix.c | 16 ++++++++++++++-- > configure | 19 +++++++++++++++++++ > 2 files changed, 33 insertions(+), 2 deletions(-) Okay, now the "ret" in handle_aiocb_write_zeroes() is necessary, so please disregard my statement about removing it in patch 3. > diff --git a/block/raw-posix.c b/block/raw-posix.c > index 24e1fab..3c35b2f 100644 > --- a/block/raw-posix.c > +++ b/block/raw-posix.c > @@ -60,7 +60,7 @@ > #define FS_NOCOW_FL 0x00800000 /* Do not cow file */ > #endif > #endif > -#ifdef CONFIG_FALLOCATE_PUNCH_HOLE > +#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) || defined(CONFIG_FALLOCATE_ZERO_RANGE) > #include > #endif > #if defined (__FreeBSD__) || defined(__FreeBSD_kernel__) > @@ -902,7 +902,7 @@ static int translate_err(int err) > return err; > } > > -#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) > +#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) || defined(CONFIG_FALLOCATE_ZERO_RANGE) > static int do_fallocate(int fd, int mode, off_t offset, off_t len) > { > do { > @@ -955,6 +955,18 @@ static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb) > } > #endif > > +#ifdef CONFIG_FALLOCATE_ZERO_RANGE > + if (s->has_write_zeroes) { > + ret = do_fallocate(s->fd, FALLOC_FL_ZERO_RANGE, > + aiocb->aio_offset, aiocb->aio_nbytes); > + if (ret == 0 || ret != -ENOTSUP) { > + return ret; > + } > + s->has_write_zeroes = false; > + return ret; > + } First, you probably want to simply fall through here; right now, you are immediately failing with -ENOTSUP on the first call, but falling through on the second call. After this patch, it doesn't make a difference, but after the next one, it might. Second, while using s->has_write_zeroes here seems correct to me, I personally don't like sharing it with handle_aiocb_write_zeroes_block(); and if you do introduce a new flag like "has_zero_range", please don't make it a bit field (I will give you an R-b regardless of whether you make it a bit field or not, I just won't like it). Feel free to keep has_write_zeroes, though, while it doesn't look good to me it certainly is correct from a technical perspective. Max