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? ;) Acked-by: David Hildenbrand (Arm) <[email protected]> -- Cheers, David
