On Tue, Aug 11, 2026 at 06:53:05PM +0200, David Hildenbrand (Arm) wrote: > On 8/11/26 18:51, Lorenzo Stoakes (ARM) wrote: > > On Tue, Aug 11, 2026 at 06:44:01PM +0200, David Hildenbrand (Arm) wrote: > >>> > >>> Since copy_vma_and_data() which calls copy_vma() intends to reference the > >>> old VMA after the merge, it must have this pointer updated. > >>> > >>> This kind of self-merge is not possible with a succeeding merge, as the > >>> merge always prefers to expand the preceding VMA if possible. > >>> > >>> copy_vma() accounts for this by explicitly checking to see if a self-merge > >>> occurred and updating the vmap pointer if so. However it incorrect did so > >>> even for a subsequent merge (this is simply a noop so it had no impact). > >> > >> Took me longer than it should to find out that this is no real fix ;) > >> > >>> > >>> So change this to only check for the case which matters - a backwards > >>> merge - and rearrange the parameters to make it clearer we're doing that - > >>> i.e. check new_vma->vm_start < old_vma_start (having already renamed > >>> vma_start to old_vma_start to make it clear this is the previous VMA). > >>> > >>> Also update the existing wall-of-text comment to be a lot clearer. > >>> > >>> While we're here, replace the VM_BUG_ON_VMA() with a VM_WARN_ON_ONCE_VMA() > >>> and update the VMA userland tests accordingly. > >>> > >>> No functional change intended. > >>> > >>> Signed-off-by: Lorenzo Stoakes (ARM) <[email protected]> > >>> --- > >> I skimmed over it, looks correct, but the merging stuff is way over my > >> head to > >> confidentially give a RB tag her :) > > > > Well that's what A-b is for ;) > > Assisted-by? Half-assed-by? > > ;)
A schloppy schplatch I like? ;) > > Acked-by: David Hildenbrand (Arm) <[email protected]> Thanks! > > -- > Cheers, > > David -- Cheers, Lorenzo
