From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45718) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YGAoL-0003GX-M0 for qemu-devel@nongnu.org; Tue, 27 Jan 2015 13:24:26 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YGAoG-0000Xm-Df for qemu-devel@nongnu.org; Tue, 27 Jan 2015 13:24:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49339) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YGAoG-0000Xc-7Q for qemu-devel@nongnu.org; Tue, 27 Jan 2015 13:24:20 -0500 Message-ID: <54C7D7CC.9090604@redhat.com> Date: Tue, 27 Jan 2015 13:24:12 -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> <54C7D19F.20408@redhat.com> <54C7D6A1.6080500@openvz.org> In-Reply-To: <54C7D6A1.6080500@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 13:19, Denis V. Lunev wrote: > On 27/01/15 20:57, Max Reitz wrote: >> 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. >> > > here is a check for fallocate and posix_fallocate in configure script > > # check for fallocate > fallocate=no > cat > $TMPC << EOF > #include > > int main(void) > { > fallocate(0, 0, 0, 0); > return 0; > } > EOF > if compile_prog "" "" ; then > fallocate=yes > fi > ... > # check for posix_fallocate > posix_fallocate=no > cat > $TMPC << EOF > #include > > int main(void) > { > posix_fallocate(0, 0, 0); > return 0; > } > EOF > if compile_prog "" "" ; then > posix_fallocate=yes > fi > ... > if test "$fallocate" = "yes" ; then > echo "CONFIG_FALLOCATE=y" >> $config_host_mak > fi > ... > if test "$posix_fallocate" = "yes" ; then > echo "CONFIG_POSIX_FALLOCATE=y" >> $config_host_mak > fi > > Thus my check looks correct to me. Oh, sorry, I somehow mixed those checks. You're right. Very well then; maybe you want to mention this change in the commit message, though? Max > >>> #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 >> > ok, will do