From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54447) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dUZCZ-0005B7-RR for qemu-devel@nongnu.org; Mon, 10 Jul 2017 09:58:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dUZCY-0000IJ-IF for qemu-devel@nongnu.org; Mon, 10 Jul 2017 09:58:15 -0400 Date: Mon, 10 Jul 2017 14:58:03 +0100 From: "Daniel P. Berrange" Message-ID: <20170710135803.GE6770@redhat.com> Reply-To: "Daniel P. Berrange" References: <1498733831-15254-1-git-send-email-pl@kamp.de> <1498733831-15254-6-git-send-email-pl@kamp.de> <20170710132546.GG5772@noname.redhat.com> <20170710133459.GI5772@noname.redhat.com> <20170710134436.GB6770@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH V2 5/8] block/qcow2: read and write the compress format extension List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: Kevin Wolf , qemu-block@nongnu.org, qemu-devel@nongnu.org, lersek@redhat.com, den@openvz.org, mreitz@redhat.com, eblake@redhat.com On Mon, Jul 10, 2017 at 03:46:21PM +0200, Peter Lieven wrote: > Am 10.07.2017 um 15:44 schrieb Daniel P. Berrange: > > On Mon, Jul 10, 2017 at 03:34:59PM +0200, Kevin Wolf wrote: > > > Am 10.07.2017 um 15:29 hat Peter Lieven geschrieben: > > > > Am 10.07.2017 um 15:25 schrieb Kevin Wolf: > > > > > Am 29.06.2017 um 12:57 hat Peter Lieven geschrieben: > > > > > > we now read the extension on open and write it on update, but > > > > > > do not yet use it. > > > > > > > > > > > > Signed-off-by: Peter Lieven > > > > > > --- > > > > > > block/qcow2.c | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++-------- > > > > > > block/qcow2.h | 23 +++++++++++--- > > > > > > 2 files changed, 104 insertions(+), 19 deletions(-) > > > > > > > > > > > > diff --git a/block/qcow2.c b/block/qcow2.c > > > > > > index 308121a..39a8afc 100644 > > > > > > --- a/block/qcow2.c > > > > > > +++ b/block/qcow2.c > > > > > > @@ -63,6 +63,7 @@ typedef struct { > > > > > > #define QCOW2_EXT_MAGIC_END 0 > > > > > > #define QCOW2_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA > > > > > > #define QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857 > > > > > > +#define QCOW2_EXT_MAGIC_COMPRESS_FORMAT 0xC03183A3 > > > > > > static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename) > > > > > > { > > > > > > @@ -76,6 +77,26 @@ static int qcow2_probe(const uint8_t *buf, int buf_size, const char *filename) > > > > > > return 0; > > > > > > } > > > > > > +static int qcow2_compress_format_from_name(char *fmt) > > > > > > +{ > > > > > > + if (!fmt || !fmt[0]) { > > > > > > + return QCOW2_COMPRESS_ZLIB_COMPAT; > > > > > > + } else if (g_str_equal(fmt, "zlib")) { > > > > > > + return QCOW2_COMPRESS_ZLIB; > > > > > > + } else { > > > > > > + return -EINVAL; > > > > > > + } > > > > > > +} > > > > > It might make sense to allow specifying the old compression format in > > > > > the compression header. But I'm not so sure about using the empty string > > > > > rather than a proper name for it, and even less about not documenting > > > > > it. > > > > The old format is used if and only if the compression header is absent. > > > > It makes no sense to write a header and use the old format. The old > > > > settings are suboptimal and old versions can't open a qcow2 with a > > > > compression header anyway. > > > Your code allows an empty string in the header extension. If you don't > > > want it there, you need to reject it. > > This is a good reason to use the QAPI schema to parse the create options > > instead of doing it using qemu_opts - the QAPI schema will generate correct > > code to parse & validate enum values > > Can you then please advise where to add the schematas and which functions > to use for parsing it? You wrote that it is a bit hackish at the moment as not > everything is available in qcow2_create path. I just sent an (untested) example for patch 3 that should help. If you still have problems let me know. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|