| Message ID | 20170627192458.15519-20-eblake@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Jun 27, 2017 at 02:24:57PM -0500, Eric Blake wrote: >bdrv_is_allocated_above() was relying on intermediate->total_sectors, >which is a field that can have stale contents depending on the value >of intermediate->has_variable_length. An audit shows that we are safe >(we were first calling through bdrv_co_get_block_status() which in >turn calls bdrv_nb_sectors() and therefore just refreshed the current >length), but it's nicer to favor our accessor functions to avoid having >to repeat such an audit, even if it means refresh_total_sectors() is >called more frequently. > >Suggested-by: John Snow <jsnow@redhat.com> >Signed-off-by: Eric Blake <eblake@redhat.com> > >--- >v2: new patch >--- > block/io.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > >diff --git a/block/io.c b/block/io.c >index 0545180..5bbf153 100644 >--- a/block/io.c >+++ b/block/io.c >@@ -1924,6 +1924,7 @@ int bdrv_is_allocated_above(BlockDriverState *top, > intermediate = top; > while (intermediate && intermediate != base) { > int64_t pnum_inter; >+ int64_t size_inter; > int psectors_inter; > > ret = bdrv_is_allocated(intermediate, sector_num * BDRV_SECTOR_SIZE, >@@ -1941,13 +1942,14 @@ int bdrv_is_allocated_above(BlockDriverState *top, > > /* > * [sector_num, nb_sectors] is unallocated on top but intermediate >- * might have >- * >- * [sector_num+x, nr_sectors] allocated. >+ * might have [sector_num+x, nb_sectors-x] allocated. > */ >+ size_inter = bdrv_nb_sectors(intermediate); >+ if (size_inter < 0) { >+ return size_inter; >+ } > if (n > psectors_inter && >- (intermediate == top || >- sector_num + psectors_inter < intermediate->total_sectors)) { >+ (intermediate == top || sector_num + psectors_inter < size_inter)) { > n = psectors_inter; > } > >-- >2.9.4 Reviewed-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
On Tue, Jun 27, 2017 at 02:24:57PM -0500, Eric Blake wrote: > bdrv_is_allocated_above() was relying on intermediate->total_sectors, > which is a field that can have stale contents depending on the value > of intermediate->has_variable_length. An audit shows that we are safe > (we were first calling through bdrv_co_get_block_status() which in > turn calls bdrv_nb_sectors() and therefore just refreshed the current > length), but it's nicer to favor our accessor functions to avoid having > to repeat such an audit, even if it means refresh_total_sectors() is > called more frequently. > > Suggested-by: John Snow <jsnow@redhat.com> > Signed-off-by: Eric Blake <eblake@redhat.com> > Reviewed-by: Jeff Cody <jcody@redhat.com> > --- > v2: new patch > --- > block/io.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/block/io.c b/block/io.c > index 0545180..5bbf153 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1924,6 +1924,7 @@ int bdrv_is_allocated_above(BlockDriverState *top, > intermediate = top; > while (intermediate && intermediate != base) { > int64_t pnum_inter; > + int64_t size_inter; > int psectors_inter; > > ret = bdrv_is_allocated(intermediate, sector_num * BDRV_SECTOR_SIZE, > @@ -1941,13 +1942,14 @@ int bdrv_is_allocated_above(BlockDriverState *top, > > /* > * [sector_num, nb_sectors] is unallocated on top but intermediate > - * might have > - * > - * [sector_num+x, nr_sectors] allocated. > + * might have [sector_num+x, nb_sectors-x] allocated. > */ > + size_inter = bdrv_nb_sectors(intermediate); > + if (size_inter < 0) { > + return size_inter; > + } > if (n > psectors_inter && > - (intermediate == top || > - sector_num + psectors_inter < intermediate->total_sectors)) { > + (intermediate == top || sector_num + psectors_inter < size_inter)) { > n = psectors_inter; > } > > -- > 2.9.4 > >
diff --git a/block/io.c b/block/io.c index 0545180..5bbf153 100644 --- a/block/io.c +++ b/block/io.c @@ -1924,6 +1924,7 @@ int bdrv_is_allocated_above(BlockDriverState *top, intermediate = top; while (intermediate && intermediate != base) { int64_t pnum_inter; + int64_t size_inter; int psectors_inter; ret = bdrv_is_allocated(intermediate, sector_num * BDRV_SECTOR_SIZE, @@ -1941,13 +1942,14 @@ int bdrv_is_allocated_above(BlockDriverState *top, /* * [sector_num, nb_sectors] is unallocated on top but intermediate - * might have - * - * [sector_num+x, nr_sectors] allocated. + * might have [sector_num+x, nb_sectors-x] allocated. */ + size_inter = bdrv_nb_sectors(intermediate); + if (size_inter < 0) { + return size_inter; + } if (n > psectors_inter && - (intermediate == top || - sector_num + psectors_inter < intermediate->total_sectors)) { + (intermediate == top || sector_num + psectors_inter < size_inter)) { n = psectors_inter; }
bdrv_is_allocated_above() was relying on intermediate->total_sectors, which is a field that can have stale contents depending on the value of intermediate->has_variable_length. An audit shows that we are safe (we were first calling through bdrv_co_get_block_status() which in turn calls bdrv_nb_sectors() and therefore just refreshed the current length), but it's nicer to favor our accessor functions to avoid having to repeat such an audit, even if it means refresh_total_sectors() is called more frequently. Suggested-by: John Snow <jsnow@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com> --- v2: new patch --- block/io.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)