Re: [Qemu-devel] [PATCH v2 1/5] qcow2: Add corrupt bit

[Max Reitz]

Am 29.08.2013 10:23, schrieb Kevin Wolf:
> Am 28.08.2013 um 16:55 hat Max Reitz geschrieben:
> > This adds an incompatible bit indicating corruption to qcow2. Any image
> > with this bit set may not be written to unless for repairing (and
> > subsequently clearing the bit if the repair has been successful).
> >
> > Signed-off-by: Max Reitz <address@hidden>
> > ---
> >   block/qcow2.c              | 45 +++++++++++++++++++++++++++++++++++++++++++++
> >   block/qcow2.h              |  7 ++++++-
> >   docs/specs/qcow2.txt       |  7 ++++++-
> >   tests/qemu-iotests/031.out | 12 ++++++------
> >   tests/qemu-iotests/036.out |  2 +-
> >   5 files changed, 64 insertions(+), 9 deletions(-)
> > @@ -402,6 +433,15 @@ static int qcow2_open(BlockDriverState *bs, QDict 
> > *options, int flags)
> >           goto fail;
> >       }
> >   
> > +    if (s->incompatible_features & QCOW2_INCOMPAT_CORRUPT) {
> > +        /* Corrupt images may not be written to unless they are being repaired
> > +         */
> > +        if ((flags & BDRV_O_RDWR) && !(flags & BDRV_O_CHECK)) {
> > +            ret = -EACCES;
> Perhaps a (q)error_report() call would be appropriate so that the user
> isn't confused with only the "Permission denied" message
Seems reasonable.
> (should it be
> EPERM rather than EACCES, too? Or maybe EROFS?)
I chose the value based on the following:
$ touch foo
$ chmod -w foo
$ echo 'bar' > foo
zsh: permission denied: foo
(which is EACCES)

EROFS sounds nice, but I wouldn't go for it since it's the image that's 
read-only and not the underlying FS (which I think EROFS is for…?)


Max