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由 Hugh Dickins 提交于
I've hit the "address >= vma->vm_end" check in do_page_add_anon_rmap() just once. The stack showed khugepaged allocation trying to compact pages: the call to page_add_anon_rmap() coming from remove_migration_pte(). That path holds anon_vma lock, but does not hold mmap_sem: it can therefore race with a split_vma(), and in commit 5f70b962 "mmap: avoid unnecessary anon_vma lock" we just took away the anon_vma lock protection when adjusting vma->vm_end. I don't think that particular BUG_ON ever caught anything interesting, so better replace it by a comment, than reinstate the anon_vma locking. Signed-off-by: NHugh Dickins <hughd@google.com> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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