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Re: [Qemu-devel] [Qemu-block] [PATCH v2 02/16] block-backend: Add blk_re
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [Qemu-block] [PATCH v2 02/16] block-backend: Add blk_request_perm |
Date: |
Wed, 24 May 2017 10:16:48 +0800 |
User-agent: |
Mutt/1.8.0 (2017-02-23) |
On Thu, 05/11 15:32, Stefan Hajnoczi wrote:
> On Wed, Apr 19, 2017 at 05:43:42PM +0800, Fam Zheng wrote:
> > This function tries to request, if not granted yet, for the given
> > permissions.
> >
> > Signed-off-by: Fam Zheng <address@hidden>
> > ---
> > block/block-backend.c | 12 ++++++++++++
> > include/sysemu/block-backend.h | 1 +
> > 2 files changed, 13 insertions(+)
> >
> > diff --git a/block/block-backend.c b/block/block-backend.c
> > index 7405024..6bdd9ce 100644
> > --- a/block/block-backend.c
> > +++ b/block/block-backend.c
> > @@ -629,6 +629,18 @@ void blk_resume_after_migration(Error **errp)
> > }
> > }
> >
> > +int blk_request_perm(BlockBackend *blk, uint64_t perm, Error **errp)
> > +{
> > + uint64_t blk_perm, shared_perm;
> > +
> > + blk_get_perm(blk, &blk_perm, &shared_perm);
> > + if ((blk_perm & perm) == perm) {
> > + return 0;
> > + }
> > + blk_perm |= perm;
> > + return blk_set_perm(blk, blk_perm, shared_perm, errp);
> > +}
>
> I'm slightly confused about why this function is needed. blk_set_perm()
> doesn't do quite the right thing?
Sorry for the late reply!
I think blk_set_perm() always calls bs->drv->bdrv_check_perm() even when the
required perm bits are already acquired.
Fam