From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43915) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YO2Rj-0001rg-34 for qemu-devel@nongnu.org; Wed, 18 Feb 2015 06:05:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YO2Rf-00046T-W8 for qemu-devel@nongnu.org; Wed, 18 Feb 2015 06:05:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38010) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YO2Rf-00046I-MD for qemu-devel@nongnu.org; Wed, 18 Feb 2015 06:05:31 -0500 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id t1IB5UMb028087 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Wed, 18 Feb 2015 06:05:31 -0500 Date: Wed, 18 Feb 2015 12:05:29 +0100 From: Kevin Wolf Message-ID: <20150218110529.GC4996@noname.str.redhat.com> References: <1423600146-7642-1-git-send-email-mreitz@redhat.com> <1423600146-7642-12-git-send-email-mreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1423600146-7642-12-git-send-email-mreitz@redhat.com> Subject: Re: [Qemu-devel] [PATCH v6 11/24] qcow2: refcount_order parameter for qcow2_create2 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz Cc: qemu-devel@nongnu.org, Stefan Hajnoczi Am 10.02.2015 um 21:28 hat Max Reitz geschrieben: > Add a refcount_order parameter to qcow2_create2(), use that value for > the image header and for calculating the size required for > preallocation. > > For now, always pass 4. > > This addition requires changes to the calculation of the file size for > the "full" and "falloc" preallocation modes. That in turn is a nice > opportunity to add a comment about that calculation not necessarily > being exact (and that being intentional). > > Signed-off-by: Max Reitz > Reviewed-by: Eric Blake > Reviewed-by: Stefan Hajnoczi > --- > block/qcow2.c | 46 +++++++++++++++++++++++++++++++++++----------- > 1 file changed, 35 insertions(+), 11 deletions(-) > > diff --git a/block/qcow2.c b/block/qcow2.c > index e563a30..b7c023e 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c > @@ -1783,7 +1783,7 @@ static int preallocate(BlockDriverState *bs) > static int qcow2_create2(const char *filename, int64_t total_size, > const char *backing_file, const char *backing_format, > int flags, size_t cluster_size, PreallocMode prealloc, > - QemuOpts *opts, int version, > + QemuOpts *opts, int version, int refcount_order, > Error **errp) > { > /* Calculate cluster_bits */ > @@ -1816,9 +1816,21 @@ static int qcow2_create2(const char *filename, int64_t total_size, > int ret; > > if (prealloc == PREALLOC_MODE_FULL || prealloc == PREALLOC_MODE_FALLOC) { > + /* Note: The following calculation does not need to be exact; if it is a > + * bit off, either some bytes will be "leaked" (which is fine) or we > + * will need to increase the file size by some bytes (which is fine, > + * too, as long as the bulk is allocated here). Therefore, using > + * floating point arithmetic is fine. */ > int64_t meta_size = 0; > uint64_t nreftablee, nrefblocke, nl1e, nl2e; > int64_t aligned_total_size = align_offset(total_size, cluster_size); > + int refblock_bits, refblock_size; > + /* refcount entry size in bytes */ > + double rces = (1 << refcount_order) / 8.; Not objecting, but we need to be careful with floating point calculations as the floating point state is not saved in coroutine switches. Kevin