From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35938) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7kSZ-00039K-47 for qemu-devel@nongnu.org; Wed, 14 Mar 2012 05:25:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S7kSF-0006sE-0d for qemu-devel@nongnu.org; Wed, 14 Mar 2012 05:25:30 -0400 Received: from mail-lb0-f173.google.com ([209.85.217.173]:46225) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7kSE-0006rX-Mb for qemu-devel@nongnu.org; Wed, 14 Mar 2012 05:25:10 -0400 Received: by lbon3 with SMTP id n3so732218lbo.4 for ; Wed, 14 Mar 2012 02:25:08 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1331655771-10868-1-git-send-email-mjt@msgid.tls.msk.ru> References: <1331655521-5986-1-git-send-email-mjt@msgid.tls.msk.ru> <1331655771-10868-1-git-send-email-mjt@msgid.tls.msk.ru> Date: Wed, 14 Mar 2012 09:25:08 +0000 Message-ID: From: Stefan Hajnoczi Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH (trivial)] no need to use bdrv_pread() in format guessing code when we can use bdrv_read() directly List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Tokarev Cc: qemu-devel@nongnu.org On Tue, Mar 13, 2012 at 4:22 PM, Michael Tokarev wrote: > [Sorry - sent the wrong patch, should have been > BDRV_SECTOR_SIZE, not BDRV_BLOCK_SIZE....] > > block.c:find_image_format() calls bdrv_pread() to read first 2048 > bytes from the device to guess its format. =A0This function can use > bdrv_read() directly since the the read is done on sector boundary. > > Signed-off-by: Michael Tokarev > --- > =A0block.c | =A0 =A02 +- > =A01 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/block.c b/block.c > index b88ee90..b3af1f6 100644 > --- a/block.c > +++ b/block.c > @@ -469,7 +469,7 @@ static int find_image_format(const char *filename, Bl= ockDriver **pdrv) > =A0 =A0 =A0 =A0 return ret; > =A0 =A0 } > > - =A0 =A0ret =3D bdrv_pread(bs, 0, buf, sizeof(buf)); > + =A0 =A0ret =3D bdrv_read(bs, 0, buf, sizeof(buf) / BDRV_SECTOR_SIZE); Why do this? The code is nicer to read without the sector division and there's no real difference at execution time. Stefan