From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=48294 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1ObH4r-0005vb-45 for qemu-devel@nongnu.org; Tue, 20 Jul 2010 13:58:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1ObH4p-0001UB-UE for qemu-devel@nongnu.org; Tue, 20 Jul 2010 13:58:01 -0400 Received: from mail-gw0-f45.google.com ([74.125.83.45]:48789) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1ObH4p-0001U6-Ra for qemu-devel@nongnu.org; Tue, 20 Jul 2010 13:57:59 -0400 Received: by gwj21 with SMTP id 21so3047224gwj.4 for ; Tue, 20 Jul 2010 10:57:59 -0700 (PDT) Message-ID: <4C45E3A3.6020708@codemonkey.ws> Date: Tue, 20 Jul 2010 12:57:55 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] Disable O_DIRECT for physical CDROM/DVD drives References: <1279639056-20465-1-git-send-email-Jes.Sorensen@redhat.com> <78CCC2B7-3124-4B24-9A96-771B8A6D4C27@claunia.com> In-Reply-To: <78CCC2B7-3124-4B24-9A96-771B8A6D4C27@claunia.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Natalia Portillo Cc: Jes.Sorensen@redhat.com, qemu-devel@nongnu.org On 07/20/2010 11:45 AM, Natalia Portillo wrote: > El 20/07/2010, a las 16:17, Jes.Sorensen@redhat.com escribió: > > >> From: Jes Sorensen >> >> O_DIRECT (cache=none) requires sector alignment, however the physical >> sector size of CDROM/DVD drives is 2048, as opposed to most disk >> devices which use 512. QEMU is hard coding 512 all over the place, so >> allowing O_DIRECT for CDROM/DVD devices does not work. >> > What about if the device is a 4096 byte/sector hard disk, a 512 byte/sector CD-ROM (IRIX ones), a 2048 byte/sector magnetooptical? > BlockDriverStates need to handle non-aligned reads/writes. As I mentioned earlier, we need cdrom_pread/cdrom_pwrite functions that do RMWs as necessary. Regards, Anthony Liguori > We should get rid of that hard codes and use real values. > > >> Signed-off-by: Jes Sorensen >> --- >> block/raw-posix.c | 5 +++++ >> 1 files changed, 5 insertions(+), 0 deletions(-) >> >> diff --git a/block/raw-posix.c b/block/raw-posix.c >> index 291699f..0ea79b6 100644 >> --- a/block/raw-posix.c >> +++ b/block/raw-posix.c >> @@ -1139,6 +1139,11 @@ static int cdrom_open(BlockDriverState *bs, const char *filename, int flags) >> BDRVRawState *s = bs->opaque; >> >> s->type = FTYPE_CD; >> + if (flags& BDRV_O_NOCACHE) { >> + fprintf(stderr, "Disabling unsupported O_DIRECT (cache=none) for " >> + "CDROM/DVD device (%s)\n", filename); >> + flags&= ~BDRV_O_NOCACHE; >> + } >> >> /* open will not fail even if no CD is inserted, so add O_NONBLOCK */ >> return raw_open_common(bs, filename, flags, O_NONBLOCK); >> -- >> 1.7.1.1 >> >> >> > >