| Message ID | 1467273706-5732-1-git-send-email-xiecl.fnst@cn.fujitsu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 06/30 16:01, Changlong Xie wrote: > Otherwise, we could never trigger assert(!bitmap->successor) > > Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com> > --- > block/dirty-bitmap.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c > index 4902ca5..e9df5ac 100644 > --- a/block/dirty-bitmap.c > +++ b/block/dirty-bitmap.c > @@ -131,7 +131,6 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs, > if (bdrv_dirty_bitmap_frozen(bitmap)) { > error_setg(errp, "Cannot create a successor for a bitmap that is " > "currently frozen"); > - return -1; > } > assert(!bitmap->successor); This is wrong. Then we will always trigger assert for a frozen bitmap. Fam
On 06/30/2016 04:25 PM, Fam Zheng wrote: > On Thu, 06/30 16:01, Changlong Xie wrote: >> Otherwise, we could never trigger assert(!bitmap->successor) >> >> Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com> >> --- >> block/dirty-bitmap.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c >> index 4902ca5..e9df5ac 100644 >> --- a/block/dirty-bitmap.c >> +++ b/block/dirty-bitmap.c >> @@ -131,7 +131,6 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs, >> if (bdrv_dirty_bitmap_frozen(bitmap)) { >> error_setg(errp, "Cannot create a successor for a bitmap that is " >> "currently frozen"); >> - return -1; >> } >> assert(!bitmap->successor); > > This is wrong. Then we will always trigger assert for a frozen bitmap. > IMO, when it's a frozen bitmap, we will always return -1. So "assert(!bitmap->successor)" is useless here, am i right? > Fam > > >
On Thu, Jun 30, 2016 at 04:45:52PM +0800, Changlong Xie wrote: > On 06/30/2016 04:25 PM, Fam Zheng wrote: > >On Thu, 06/30 16:01, Changlong Xie wrote: > >>Otherwise, we could never trigger assert(!bitmap->successor) > >> > >>Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com> > >>--- > >> block/dirty-bitmap.c | 1 - > >> 1 file changed, 1 deletion(-) > >> > >>diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c > >>index 4902ca5..e9df5ac 100644 > >>--- a/block/dirty-bitmap.c > >>+++ b/block/dirty-bitmap.c > >>@@ -131,7 +131,6 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs, > >> if (bdrv_dirty_bitmap_frozen(bitmap)) { > >> error_setg(errp, "Cannot create a successor for a bitmap that is " > >> "currently frozen"); > >>- return -1; > >> } > >> assert(!bitmap->successor); > > > >This is wrong. Then we will always trigger assert for a frozen bitmap. > > > > IMO, when it's a frozen bitmap, we will always return -1. So > "assert(!bitmap->successor)" is useless here, am i right? > I don't see a path where the assert could trigger, so I would agree that the assert itself, while harmless, is not necessary (although it could be argued it is in place in case the code above it changes in a way that does not check bitmap->successor). That doesn't mean we want to try and trigger an assert, however! :) The error return is the proper error handling -- we don't expect that asserts should ever be encountered QEMU, if one happens that is a sign of a bug. Jeff
On 06/30/2016 10:00 AM, Jeff Cody wrote: > On Thu, Jun 30, 2016 at 04:45:52PM +0800, Changlong Xie wrote: >> On 06/30/2016 04:25 PM, Fam Zheng wrote: >>> On Thu, 06/30 16:01, Changlong Xie wrote: >>>> Otherwise, we could never trigger assert(!bitmap->successor) >>>> >>>> Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com> >>>> --- >>>> block/dirty-bitmap.c | 1 - >>>> 1 file changed, 1 deletion(-) >>>> >>>> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c >>>> index 4902ca5..e9df5ac 100644 >>>> --- a/block/dirty-bitmap.c >>>> +++ b/block/dirty-bitmap.c >>>> @@ -131,7 +131,6 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs, >>>> if (bdrv_dirty_bitmap_frozen(bitmap)) { >>>> error_setg(errp, "Cannot create a successor for a bitmap that is " >>>> "currently frozen"); >>>> - return -1; >>>> } >>>> assert(!bitmap->successor); >>> >>> This is wrong. Then we will always trigger assert for a frozen bitmap. >>> >> >> IMO, when it's a frozen bitmap, we will always return -1. So >> "assert(!bitmap->successor)" is useless here, am i right? >> > > I don't see a path where the assert could trigger, so I would agree that the > assert itself, while harmless, is not necessary (although it could be argued > it is in place in case the code above it changes in a way that does not > check bitmap->successor). > > That doesn't mean we want to try and trigger an assert, however! :) The > error return is the proper error handling -- we don't expect that asserts > should ever be encountered QEMU, if one happens that is a sign of a bug. > > Jeff > The assert was indeed added to ensure that if the valid states of the bitmap later expanded or changed, that the status checkers (e.g. bdrv_dirty_bitmap_frozen()) were changed to match.
On 07/01/2016 02:18 AM, John Snow wrote: > > > On 06/30/2016 10:00 AM, Jeff Cody wrote: >> On Thu, Jun 30, 2016 at 04:45:52PM +0800, Changlong Xie wrote: >>> On 06/30/2016 04:25 PM, Fam Zheng wrote: >>>> On Thu, 06/30 16:01, Changlong Xie wrote: >>>>> Otherwise, we could never trigger assert(!bitmap->successor) >>>>> >>>>> Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com> >>>>> --- >>>>> block/dirty-bitmap.c | 1 - >>>>> 1 file changed, 1 deletion(-) >>>>> >>>>> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c >>>>> index 4902ca5..e9df5ac 100644 >>>>> --- a/block/dirty-bitmap.c >>>>> +++ b/block/dirty-bitmap.c >>>>> @@ -131,7 +131,6 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs, >>>>> if (bdrv_dirty_bitmap_frozen(bitmap)) { >>>>> error_setg(errp, "Cannot create a successor for a bitmap that is " >>>>> "currently frozen"); >>>>> - return -1; >>>>> } >>>>> assert(!bitmap->successor); >>>> >>>> This is wrong. Then we will always trigger assert for a frozen bitmap. >>>> >>> >>> IMO, when it's a frozen bitmap, we will always return -1. So >>> "assert(!bitmap->successor)" is useless here, am i right? >>> >> >> I don't see a path where the assert could trigger, so I would agree that the >> assert itself, while harmless, is not necessary (although it could be argued >> it is in place in case the code above it changes in a way that does not >> check bitmap->successor). Agree >> >> That doesn't mean we want to try and trigger an assert, however! :) The >> error return is the proper error handling -- we don't expect that asserts >> should ever be encountered QEMU, if one happens that is a sign of a bug. >> Got it >> Jeff >> > > The assert was indeed added to ensure that if the valid states of the > bitmap later expanded or changed, that the status checkers (e.g. > bdrv_dirty_bitmap_frozen()) were changed to match. > Thanks for all explanations. Although my brain always forces to think it's a redundant execution path, but since it's harmless, let's keep it. > > . >
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c index 4902ca5..e9df5ac 100644 --- a/block/dirty-bitmap.c +++ b/block/dirty-bitmap.c @@ -131,7 +131,6 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs, if (bdrv_dirty_bitmap_frozen(bitmap)) { error_setg(errp, "Cannot create a successor for a bitmap that is " "currently frozen"); - return -1; } assert(!bitmap->successor);
Otherwise, we could never trigger assert(!bitmap->successor) Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com> --- block/dirty-bitmap.c | 1 - 1 file changed, 1 deletion(-)