| Message ID | 20170419094356.19826-3-famz@redhat.com |
|---|---|
| State | New |
| Headers | show |
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 <famz@redhat.com> > --- > 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?
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 <famz@redhat.com> > > --- > > 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
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); +} + static int blk_do_attach_dev(BlockBackend *blk, void *dev) { if (blk->dev) { diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h index 7462228..537f92f 100644 --- a/include/sysemu/block-backend.h +++ b/include/sysemu/block-backend.h @@ -116,6 +116,7 @@ bool bdrv_is_root_node(BlockDriverState *bs); int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm, Error **errp); void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm); +int blk_request_perm(BlockBackend *blk, uint64_t perm, Error **errp); void blk_set_allow_write_beyond_eof(BlockBackend *blk, bool allow); void blk_iostatus_enable(BlockBackend *blk);
This function tries to request, if not granted yet, for the given permissions. Signed-off-by: Fam Zheng <famz@redhat.com> --- block/block-backend.c | 12 ++++++++++++ include/sysemu/block-backend.h | 1 + 2 files changed, 13 insertions(+)