Hi Shaohua,

On Thu, Feb 16, 2017 at 04:27:18PM -0800, Shaohua Li wrote:

On Thu, Feb 16, 2017 at 01:40:18PM -0500, Johannes Weiner wrote:

quoted

On Tue, Feb 14, 2017 at 11:36:09AM -0800, Shaohua Li wrote:

quoted

@@ -1419,11 +1419,18 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
 			VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page),
 				page);
 
-			if (!PageDirty(page) && (flags & TTU_LZFREE)) {
-				/* It's a freeable page by MADV_FREE */
-				dec_mm_counter(mm, MM_ANONPAGES);
-				rp->lazyfreed++;
-				goto discard;
+			if (flags & TTU_LZFREE) {
+				if (!PageDirty(page)) {
+					/* It's a freeable page by MADV_FREE */
+					dec_mm_counter(mm, MM_ANONPAGES);
+					rp->lazyfreed++;
+					goto discard;
+				} else {
+					set_pte_at(mm, address, pvmw.pte, pteval);
+					ret = SWAP_FAIL;
+					page_vma_mapped_walk_done(&pvmw);
+					break;
+				}

I don't understand why we need the TTU_LZFREE bit in general. More on
that below at the callsite.

Sounds useless flag, don't see any reason we shouldn't free the MADV_FREE page
in places other than reclaim. Looks TTU_UNMAP is useless too..

Agree on TTU_UNMAP but for example, THP split doesn't mean free lazyfree pages,
I think.

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