linux-kernel - [PATCH v2 07/32] mm/page_vma_mapped: reformat map

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Message-ID: <bf723f59-e3fc-6839-1cc3-c0631ee248bc@google.com>
Date:   Thu, 8 Jun 2023 18:14:12 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Yang Shi <shy828301@...il.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Peter Xu <peterx@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Steven Price <steven.price@....com>,
        SeongJae Park <sj@...nel.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Huang Ying <ying.huang@...el.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Zack Rusin <zackr@...are.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Minchan Kim <minchan@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Song Liu <song@...nel.org>,
        Thomas Hellstrom <thomas.hellstrom@...ux.intel.com>,
        Ryan Roberts <ryan.roberts@....com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v2 07/32] mm/page_vma_mapped: reformat map_pte() with less
 indentation

No functional change here, but adjust the format of map_pte() so that the
following commit will be easier to read: separate out the PVMW_SYNC case
first, and remove two levels of indentation from the ZONE_DEVICE case.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 mm/page_vma_mapped.c | 65 +++++++++++++++++++++++---------------------
 1 file changed, 34 insertions(+), 31 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 007dc7456f0e..947dc7491815 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -15,38 +15,41 @@ static inline bool not_found(struct page_vma_mapped_walk *pvmw)
 
 static bool map_pte(struct page_vma_mapped_walk *pvmw)
 {
-	pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
-	if (!(pvmw->flags & PVMW_SYNC)) {
-		if (pvmw->flags & PVMW_MIGRATION) {
-			if (!is_swap_pte(*pvmw->pte))
-				return false;
-		} else {
-			/*
-			 * We get here when we are trying to unmap a private
-			 * device page from the process address space. Such
-			 * page is not CPU accessible and thus is mapped as
-			 * a special swap entry, nonetheless it still does
-			 * count as a valid regular mapping for the page (and
-			 * is accounted as such in page maps count).
-			 *
-			 * So handle this special case as if it was a normal
-			 * page mapping ie lock CPU page table and returns
-			 * true.
-			 *
-			 * For more details on device private memory see HMM
-			 * (include/linux/hmm.h or mm/hmm.c).
-			 */
-			if (is_swap_pte(*pvmw->pte)) {
-				swp_entry_t entry;
+	if (pvmw->flags & PVMW_SYNC) {
+		/* Use the stricter lookup */
+		pvmw->pte = pte_offset_map_lock(pvmw->vma->vm_mm, pvmw->pmd,
+						pvmw->address, &pvmw->ptl);
+		return true;
+	}
 
-				/* Handle un-addressable ZONE_DEVICE memory */
-				entry = pte_to_swp_entry(*pvmw->pte);
-				if (!is_device_private_entry(entry) &&
-				    !is_device_exclusive_entry(entry))
-					return false;
-			} else if (!pte_present(*pvmw->pte))
-				return false;
-		}
+	pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address);
+	if (pvmw->flags & PVMW_MIGRATION) {
+		if (!is_swap_pte(*pvmw->pte))
+			return false;
+	} else if (is_swap_pte(*pvmw->pte)) {
+		swp_entry_t entry;
+		/*
+		 * Handle un-addressable ZONE_DEVICE memory.
+		 *
+		 * We get here when we are trying to unmap a private
+		 * device page from the process address space. Such
+		 * page is not CPU accessible and thus is mapped as
+		 * a special swap entry, nonetheless it still does
+		 * count as a valid regular mapping for the page
+		 * (and is accounted as such in page maps count).
+		 *
+		 * So handle this special case as if it was a normal
+		 * page mapping ie lock CPU page table and return true.
+		 *
+		 * For more details on device private memory see HMM
+		 * (include/linux/hmm.h or mm/hmm.c).
+		 */
+		entry = pte_to_swp_entry(*pvmw->pte);
+		if (!is_device_private_entry(entry) &&
+		    !is_device_exclusive_entry(entry))
+			return false;
+	} else if (!pte_present(*pvmw->pte)) {
+		return false;
 	}
 	pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
 	spin_lock(pvmw->ptl);
-- 
2.35.3