mm: simplify try_to_unmap_one() (caed0f48) · Commits · 戴 / test

SWAP_MLOCK mean "We marked the page as PG_MLOCK, please move it to unevictable-lru". So, following code is easy confusable. if (vma->vm_flags & VM_LOCKED) { ret = SWAP_MLOCK; goto out_unmap; } Plus, if the VMA doesn't have VM_LOCKED, We don't need to check the needed of calling mlock_vma_page(). Also, add some commentary to try_to_unmap_one(). Acked-by:

Hugh Dickins <hugh.dickins@tiscali.co.uk> Signed-off-by:

KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/rmap.c

+22 −13

Original line number	Diff line number	Diff line
		@@ -789,10 +789,9 @@ int try_to_unmap_one(struct page page, struct vm_area_struct vma,
		* skipped over this mm) then we should reactivate it.
		*/
		if (!(flags & TTU_IGNORE_MLOCK)) {
		if (vma->vm_flags & VM_LOCKED) {
		ret = SWAP_MLOCK;
		goto out_unmap;
		}
		if (vma->vm_flags & VM_LOCKED)
		goto out_mlock;

		if (TTU_ACTION(flags) == TTU_MUNLOCK)
		goto out_unmap;
		}
		@@ -865,9 +864,21 @@ int try_to_unmap_one(struct page page, struct vm_area_struct vma,

		out_unmap:
		pte_unmap_unlock(pte, ptl);
		out:
		return ret;

		out_mlock:
		pte_unmap_unlock(pte, ptl);

		if (ret == SWAP_MLOCK) {
		ret = SWAP_AGAIN;

		/*
		* We need mmap_sem locking, Otherwise VM_LOCKED check makes
		* unstable result and race. Plus, We can't wait here because
		* we now hold anon_vma->lock or mapping->i_mmap_lock.
		* if trylock failed, the page remain in evictable lru and later
		* vmscan could retry to move the page to unevictable lru if the
		* page is actually mlocked.
		*/
		if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
		if (vma->vm_flags & VM_LOCKED) {
		mlock_vma_page(page);
		@@ -875,8 +886,6 @@ out_unmap:
		}
		up_read(&vma->vm_mm->mmap_sem);
		}
		}
		out:
		return ret;
		}

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