Messages in this thread | | | Date | Fri, 20 Jun 2008 07:58:20 +0100 | From | "Jan Beulich" <> | Subject | Re: [PATCH] i386: fix vmalloc_sync_all() for Xen |
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>I think it would be better to separately test whether the vmalloc >mapping is present in the init_mm and skip the syncing loop in that >case, rather than this somewhat convoluted logic to overload the test in >vmalloc_sync_one.
That's what the x86-64 code does. When I wrote this originally, I tried to keep the pre-existing logic as much as possible, so I split out vmalloc_sync_one() by mostly moving existing code. I certainly agree that this has room for cleaning up (and then possibly including unification with x86-64).
>>>> This is a replacement of the BUG_ON() that an earlier patch from you >>>> removed: Failure of vmalloc_sync_one() must happen on the first >>>> entry or never, and this is what is being checked for here. >>>> >>>> >>> Could you add a comment? >>> >> >> Sure, though there was none originally, and the intention seemed >> quite clear to me. > >Well, looks to me like vmalloc_sync_one can only return NULL iff the >vmalloc mapping is absent in init_mm, so that's going to be invariant
Correct.
>with respect to any other pgd you pass in. So I don't think the BUG_ON >will ever fire, and it's unclear what actual logical property it's >testing for.
My point of adding the BUG_ON() is that in vmalloc_sync_all() it is not clear that vmalloc_sync_one() can fail only due to init_mm's page table not being appropriately populated. So yes, this BUG_ON() is not expected to ever fire - but isn't that a property of all BUG_ON()'s?
Jan
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