linux-kernel - [PATCH v7 4/6] mm: pvmw: add support for walking devmap pages

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Message-Id: <20220403053957.10770-5-songmuchun@bytedance.com>
Date:   Sun,  3 Apr 2022 13:39:55 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     dan.j.williams@...el.com, willy@...radead.org, jack@...e.cz,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        apopple@...dia.com, shy828301@...il.com, rcampbell@...dia.com,
        hughd@...gle.com, xiyuyang19@...an.edu.cn,
        kirill.shutemov@...ux.intel.com, zwisler@...nel.org,
        hch@...radead.org
Cc:     linux-fsdevel@...r.kernel.org, nvdimm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        duanxiongchun@...edance.com, smuchun@...il.com,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v7 4/6] mm: pvmw: add support for walking devmap pages

The devmap pages can not use page_vma_mapped_walk() to check if a huge
devmap page is mapped into a vma.  Add support for walking huge devmap
pages so that DAX can use it in the next patch.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/page_vma_mapped.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 1187f9c1ec5b..3da82bf65de8 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -210,16 +210,10 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 		 */
 		pmde = READ_ONCE(*pvmw->pmd);
 
-		if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) {
+		if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
+		    (pmd_present(pmde) && pmd_devmap(pmde))) {
 			pvmw->ptl = pmd_lock(mm, pvmw->pmd);
 			pmde = *pvmw->pmd;
-			if (likely(pmd_trans_huge(pmde))) {
-				if (pvmw->flags & PVMW_MIGRATION)
-					return not_found(pvmw);
-				if (!check_pmd(pmd_pfn(pmde), pvmw))
-					return not_found(pvmw);
-				return true;
-			}
 			if (!pmd_present(pmde)) {
 				swp_entry_t entry;
 
@@ -232,6 +226,13 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 					return not_found(pvmw);
 				return true;
 			}
+			if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
+				if (pvmw->flags & PVMW_MIGRATION)
+					return not_found(pvmw);
+				if (!check_pmd(pmd_pfn(pmde), pvmw))
+					return not_found(pvmw);
+				return true;
+			}
 			/* THP pmd was split under us: handle on pte level */
 			spin_unlock(pvmw->ptl);
 			pvmw->ptl = NULL;
-- 
2.11.0