On 05/04/2017 02:30 PM, John Snow wrote: > Or, rather, force the open of a backing image if one was specified > for creation. Using a similar -unsafe option as rebase, allow qemu-img > to ignore the backing file validation if possible. > > It may not always be possible, as in the existing case of if a filesize
s/of if/when/ > for the new image was not specified. > > This is accomplished by shifting around the conditionals in > bdrv_img_create, such that a backing file is always opened unless we > provide BDRV_O_NO_BACKING. qemu-img is adjusted to pass this new flag > when -u is provided to create. > > Sorry for the heinous looking diffstat, but it's mostly whitespace. > Indeed, reviewing under 'git diff -b' proved fruitful. > Inspired by: https://bugzilla.redhat.com/show_bug.cgi?id=1213786 > > Signed-off-by: John Snow <js...@redhat.com> > --- > block.c | 75 > +++++++++++++++++++++++----------------------- > qemu-img-cmds.hx | 4 +-- Conflicts with the documentation patch for [-b backing_file] (already on PULL request: https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg05816.html so you'll have to rebase, but it shouldn't be too difficult. > qemu-img.c | 15 ++++++---- > tests/qemu-iotests/082 | 4 +-- > tests/qemu-iotests/082.out | 4 +-- > 5 files changed, 54 insertions(+), 48 deletions(-) > > diff --git a/block.c b/block.c > index 5db266b..da28052 100644 > --- a/block.c > +++ b/block.c > @@ -4280,38 +4280,38 @@ void bdrv_img_create(const char *filename, const char > *fmt, > // The size for the image must always be specified, with one exception: > // If we are using a backing file, we can obtain the size from there > size = qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 0); > - if (size == -1) { Wait. How does this even work? qemu_opt_get_size() returns an unsigned value, either what was specified by the option, or else the default parameter (which we passed as 0), so how can size ever be -1? It might make sense if we had called: size = qemu_opt_get_size(opts, BLOCK_OPT_SIZE, -1); with the intent of allowing an explicit size of 0. But I'm lost as to how this code ever worked pre-patch... > + > + if (size == -1) { ...which therefore carries over to the state of things post-patch. /me goes and reads code What? if (desc && desc->def_value_str) { parse_option_size(name, desc->def_value_str, &ret, &error_abort); return ret; Oh - so THAT's how: qemu_opt_get_size_helper() ignores the 'defval' input and instead returns a DIFFERENT default associated with the QemuOpts. UGLY. But not your fault. > +++ b/qemu-img.c > @@ -145,9 +145,10 @@ static void QEMU_NORETURN help(void) > " 'snapshot_id_or_name' is deprecated, use 'snapshot_param'\n" > " instead\n" > " '-c' indicates that target image must be compressed (qcow > format only)\n" > - " '-u' enables unsafe rebasing. It is assumed that old and new > backing file\n" > - " match exactly. The image doesn't need a working backing > file before\n" > - " rebasing in this case (useful for renaming the backing > file)\n" > + " '-u' allows unsafe backing chains. For rebasing, it is assumed > that old and new \n" > + " backing file match exactly. The image doesn't need a > working backing file \n" > + " before rebasing in this case (useful for renaming the > backing file)\n" > + " For image creation, allow creating without attempting to > open the file.\n" maybe s/to open the file/to open the backing file/ > +++ b/tests/qemu-iotests/082 > @@ -85,8 +85,8 @@ run_qemu_img create -f $IMGFMT -o cluster_size=4k -o help > "$TEST_IMG" $size > run_qemu_img create -f $IMGFMT -o cluster_size=4k -o \? "$TEST_IMG" $size > > # Looks like a help option, but is part of the backing file name > -run_qemu_img create -f $IMGFMT -o backing_file="$TEST_IMG",,help "$TEST_IMG" > $size > -run_qemu_img create -f $IMGFMT -o backing_file="$TEST_IMG",,\? "$TEST_IMG" > $size > +run_qemu_img create -f $IMGFMT -u -o backing_file="$TEST_IMG",,help > "$TEST_IMG" $size > +run_qemu_img create -f $IMGFMT -u -o backing_file="$TEST_IMG",,\? > "$TEST_IMG" $size Nice test of the new usage. I like where it's headed. It will need a v2 to rebase and fix the things I pointed out, but I'm looking forward to it. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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