linux-kernel - [PATCH 07/11] mm: page_vma_mapped_walk(): add a level of indentation

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Message-ID: <efde211-f3e2-fe54-977-ef481419e7f3@google.com>
Date:   Wed, 9 Jun 2021 23:46:30 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
        Peter Xu <peterx@...hat.com>, Will Deacon <will@...nel.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 07/11] mm: page_vma_mapped_walk(): add a level of
 indentation

page_vma_mapped_walk() cleanup: add a level of indentation to much of
the body, making no functional change in this commit, but reducing the
later diff when this is all converted to a loop.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
Cc: <stable@...r.kernel.org>
---
 mm/page_vma_mapped.c | 109 +++++++++++++++++++++++----------------------
 1 file changed, 56 insertions(+), 53 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 0fe6e558d336..0840079ef7d2 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -173,65 +173,68 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 	if (pvmw->pte)
 		goto next_pte;
 restart:
-	pgd = pgd_offset(mm, pvmw->address);
-	if (!pgd_present(*pgd))
-		return false;
-	p4d = p4d_offset(pgd, pvmw->address);
-	if (!p4d_present(*p4d))
-		return false;
-	pud = pud_offset(p4d, pvmw->address);
-	if (!pud_present(*pud))
-		return false;
-
-	pvmw->pmd = pmd_offset(pud, pvmw->address);
-	/*
-	 * Make sure the pmd value isn't cached in a register by the
-	 * compiler and used as a stale value after we've observed a
-	 * subsequent update.
-	 */
-	pmde = pmd_read_atomic(pvmw->pmd);
-	barrier();
-
-	if (pmd_trans_huge(pmde) || is_pmd_migration_entry(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 (pmd_page(pmde) != page)
-				return not_found(pvmw);
-			return true;
-		}
-		if (!pmd_present(pmde)) {
-			swp_entry_t entry;
+	{
+		pgd = pgd_offset(mm, pvmw->address);
+		if (!pgd_present(*pgd))
+			return false;
+		p4d = p4d_offset(pgd, pvmw->address);
+		if (!p4d_present(*p4d))
+			return false;
+		pud = pud_offset(p4d, pvmw->address);
+		if (!pud_present(*pud))
+			return false;
 
-			if (!thp_migration_supported() ||
-			    !(pvmw->flags & PVMW_MIGRATION))
-				return not_found(pvmw);
-			entry = pmd_to_swp_entry(pmde);
-			if (!is_migration_entry(entry) ||
-			    migration_entry_to_page(entry) != page)
-				return not_found(pvmw);
-			return true;
-		}
-		/* THP pmd was split under us: handle on pte level */
-		spin_unlock(pvmw->ptl);
-		pvmw->ptl = NULL;
-	} else if (!pmd_present(pmde)) {
+		pvmw->pmd = pmd_offset(pud, pvmw->address);
 		/*
-		 * If PVMW_SYNC, take and drop THP pmd lock so that we
-		 * cannot return prematurely, while zap_huge_pmd() has
-		 * cleared *pmd but not decremented compound_mapcount().
+		 * Make sure the pmd value isn't cached in a register by the
+		 * compiler and used as a stale value after we've observed a
+		 * subsequent update.
 		 */
-		if ((pvmw->flags & PVMW_SYNC) && PageTransCompound(page)) {
-			spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
+		pmde = pmd_read_atomic(pvmw->pmd);
+		barrier();
+
+		if (pmd_trans_huge(pmde) || is_pmd_migration_entry(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 (pmd_page(pmde) != page)
+					return not_found(pvmw);
+				return true;
+			}
+			if (!pmd_present(pmde)) {
+				swp_entry_t entry;
 
-			spin_unlock(ptl);
+				if (!thp_migration_supported() ||
+				    !(pvmw->flags & PVMW_MIGRATION))
+					return not_found(pvmw);
+				entry = pmd_to_swp_entry(pmde);
+				if (!is_migration_entry(entry) ||
+				    migration_entry_to_page(entry) != page)
+					return not_found(pvmw);
+				return true;
+			}
+			/* THP pmd was split under us: handle on pte level */
+			spin_unlock(pvmw->ptl);
+			pvmw->ptl = NULL;
+		} else if (!pmd_present(pmde)) {
+			/*
+			 * If PVMW_SYNC, take and drop THP pmd lock so that we
+			 * cannot return prematurely, while zap_huge_pmd() has
+			 * cleared *pmd but not decremented compound_mapcount().
+			 */
+			if ((pvmw->flags & PVMW_SYNC) &&
+			    PageTransCompound(page)) {
+				spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
+
+				spin_unlock(ptl);
+			}
+			return false;
 		}
-		return false;
+		if (!map_pte(pvmw))
+			goto next_pte;
 	}
-	if (!map_pte(pvmw))
-		goto next_pte;
 	while (1) {
 		unsigned long end;
 
-- 
2.26.2