From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34249) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YGAOn-0005XX-WF for qemu-devel@nongnu.org; Tue, 27 Jan 2015 12:58:03 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YGAOk-0006dx-Ew for qemu-devel@nongnu.org; Tue, 27 Jan 2015 12:58:01 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35032) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YGAOk-0006dh-8c for qemu-devel@nongnu.org; Tue, 27 Jan 2015 12:57:58 -0500 Message-ID: <54C7D19F.20408@redhat.com> Date: Tue, 27 Jan 2015 12:57:51 -0500 From: Max Reitz MIME-Version: 1.0 References: <1422366699-17473-1-git-send-email-den@openvz.org> <1422366699-17473-7-git-send-email-den@openvz.org> In-Reply-To: <1422366699-17473-7-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 6/7] block/raw-posix: call plain fallocate 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: > There is a possibility that we are extending our image and thus writing > zeroes beyond the end of the file. In this case we do not need to care > about the hole to make sure that there is no data in the file under > this offset (pre-condition to fallocate(0) to work). We could simply call > fallocate(0). > > This improves the performance of writing zeroes even on really old > platforms which do not have even FALLOC_FL_PUNCH_HOLE. > > Signed-off-by: Denis V. Lunev > CC: Kevin Wolf > CC: Stefan Hajnoczi > CC: Peter Lieven > CC: Fam Zheng > --- > block/raw-posix.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/block/raw-posix.c b/block/raw-posix.c > index c039bef..fa05239 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 > -#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) || defined(CONFIG_FALLOCATE_ZERO_RANGE) > +#ifdef CONFIG_FALLOCATE This change doesn't seem right; CONFIG_FALLOCATE is set if posix_fallocate() is available, not for the Linux-specific fallocate() from linux/falloc.h. > #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) || defined(CONFIG_FALLOCATE_ZERO_RANGE) > +#ifdef CONFIG_FALLOCATE Same here. > static int do_fallocate(int fd, int mode, off_t offset, off_t len) > { > do { > @@ -981,6 +981,12 @@ static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb) > } > #endif > > +#ifdef CONFIG_FALLOCATE > + if (aiocb->aio_offset >= aiocb->bs->total_sectors << BDRV_SECTOR_BITS) { > + return do_fallocate(s->fd, 0, aiocb->aio_offset, aiocb->aio_nbytes); > + } > +#endif > + This seems fine though, but as I've asked in patch 5: Do we want to have a "has_fallocate"? Other than that, this is the first usage of bs->total_sectors in this file; raw_co_get_block_status() does a similar check, but it uses bdrv_getlength() instead. If bs->total_sectors is correct, bdrv_getlength() will actually do nothing but return bs->total_sectors * BDRV_SECTOR_SIZE; it will only do more (that is, update bs->total_sectors) if it is not correct to use bs->total_sectors (and I feel like it may not be correct because BlockDriver.has_variable_length is true). Max > s->has_write_zeroes = false; > return ret; > }