On Wed, Jan 22, 2014 at 09:54:26AM +0800, Fam Zheng wrote:
> On Tue, 01/21 11:31, Jeff Cody wrote:
> > If the top image to commit is the active layer, and also larger than
> > the base image, then an I/O error will likely be returned during
> > block-commit.
> >
> > For instance, if we have a base image with a virtual size 10G, and a
> > active layer image of size 20G, then committing the snapshot via
> > 'block-commit' will likely fail.
> >
> > This will automatically attempt to resize the base image, if the
> > active layer image to be committed is larger.
> >
> > Signed-off-by: Jeff Cody <jc...@redhat.com>
> > ---
> > block/mirror.c | 36 ++++++++++++++++++++++++++++++++++++
> > 1 file changed, 36 insertions(+)
> >
> > diff --git a/block/mirror.c b/block/mirror.c
> > index 2932bab..528b61a 100644
> > --- a/block/mirror.c
> > +++ b/block/mirror.c
> > @@ -630,11 +630,47 @@ void commit_active_start(BlockDriverState *bs,
> > BlockDriverState *base,
> > BlockDriverCompletionFunc *cb,
> > void *opaque, Error **errp)
> > {
> > + int64_t length, base_length;
> > + int orig_base_flags;
> > +
> > + orig_base_flags = bdrv_get_flags(base);
> > +
> > if (bdrv_reopen(base, bs->open_flags, errp)) {
> > return;
> > }
> > +
> > + length = bdrv_getlength(bs);
> > + base_length = bdrv_getlength(base);
> > +
> > + if (length < 0 || base_length < 0) {
>
> I prefer to add an error to errp here, at least tell which bdrv_getlength
> failed helps.
>
OK, I can do that.
> > + goto error_restore_flags;
> > + }
> > +
> > + if (length > base_length) {
> > + if (bdrv_truncate(base, length) < 0) {
> > + error_setg(errp, "Top image %s is larger than base image %s,
> > and "
> > + "resize of base image failed.",
> > + bs->filename, base->filename);
> > + goto error_restore_flags;
> > + }
> > + } else if (length < 0) {
> > + goto error_restore_flags;
> > + }
> > +
> > +
> > bdrv_ref(base);
> > mirror_start_job(bs, base, speed, 0, 0,
> > on_error, on_error, cb, opaque, errp,
> > &commit_active_job_driver, false, base);
> > + if (error_is_set(errp)) {
> > + goto error_restore_flags;
> > + }
> > +
> > + return;
> > +
> > +error_restore_flags:
> > + /* ignore error and errp for bdrv_reopen, because we want to propagate
> > + * the original error */
> > + bdrv_reopen(base, orig_base_flags, NULL);
>
> Well, I hope this never fail. (But if it does, should we do anything else than
> ignoring it?)
>
Me too :) There isn't a lot we can do but ignore it; the original
error that lead us here is most likely more important and informative
than the reopen error, so I don't think it makes sense to override
errp. And failing to restore the original flags is likely not
catastrophic (but symptomatic).
>
> > + return;
> > }
> > --
> > 1.8.3.1
> >
