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b=j9SFDCsSMmfi42b8AcdC18Tc4VNQIi3JT8PZ7mPnoDTT3poW00uK/SRcwEOod44Jy 8E5sR6Hl7ZWELgifoEQxGMMNi4NDkSZK1vj10ZH/F0lagG3djQAyAJ5UTBE1COBbm7 w9pGxCbQGjgLkEqWVN1oR02IlplgaeYDh/aIKRQbB8vKOgH5sEK3zdOlrbLuzhuhOU CJEr2eUqmlGowzt9mWhNbrCUivY2yV1T1zl8/WLLMKYAHfI+Wgpx6/XRPmte5QrUoe A62uNy3SlKZw2pEYpRDBjitoVgUT6ZND1TtimAuemUzynfmP/9yVi2BqsI9F5pkrmE 7OFRVgFeJezVA== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 23, 2020 at 03:30:04PM -0700, Ralph Campbell wrote: > When migrating the special zero page, migrate_vma_pages() calls > mmu_notifier_invalidate_range_start() before replacing the zero page > PFN in the CPU page tables. This is unnecessary since the range was > invalidated in migrate_vma_setup() and the page table entry is checked > to be sure it hasn't changed between migrate_vma_setup() and > migrate_vma_pages(). Therefore, remove the redundant invalidation. I don't follow this logic, the purpose of the invalidation is also to clear out anything that may be mirroring this VA, and "the page hasn't changed" doesn't seem to rule out that case? I'm also not sure I follow where the zero page came from? Jason