linux-kernel - [PATCH] /proc/PID/smaps: Add PMD migration entry parsing

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Message-Id: <20200331085604.1260162-1-ying.huang@intel.com>
Date:   Tue, 31 Mar 2020 16:56:04 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Huang Ying <ying.huang@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Zi Yan <ziy@...dia.com>, Vlastimil Babka <vbabka@...e.cz>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Jérôme Glisse <jglisse@...hat.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>
Subject: [PATCH] /proc/PID/smaps: Add PMD migration entry parsing

From: Huang Ying <ying.huang@...el.com>

Now, when read /proc/PID/smaps, the PMD migration entry in page table is simply
ignored.  To improve the accuracy of /proc/PID/smaps, its parsing and processing
is added.

Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Alexey Dobriyan <adobriyan@...il.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc: "Jérôme Glisse" <jglisse@...hat.com>
Cc: Yang Shi <yang.shi@...ux.alibaba.com>
---
 fs/proc/task_mmu.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8d382d4ec067..b5b3aef8cb3b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -548,8 +548,17 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
 	bool locked = !!(vma->vm_flags & VM_LOCKED);
 	struct page *page;
 
-	/* FOLL_DUMP will return -EFAULT on huge zero page */
-	page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
+	if (pmd_present(*pmd)) {
+		/* FOLL_DUMP will return -EFAULT on huge zero page */
+		page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
+	} else if (unlikely(is_swap_pmd(*pmd))) {
+		swp_entry_t entry = pmd_to_swp_entry(*pmd);
+
+		VM_BUG_ON(!is_migration_entry(entry));
+		page = migration_entry_to_page(entry);
+	} else {
+		return;
+	}
 	if (IS_ERR_OR_NULL(page))
 		return;
 	if (PageAnon(page))
@@ -578,8 +587,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 
 	ptl = pmd_trans_huge_lock(pmd, vma);
 	if (ptl) {
-		if (pmd_present(*pmd))
-			smaps_pmd_entry(pmd, addr, walk);
+		smaps_pmd_entry(pmd, addr, walk);
 		spin_unlock(ptl);
 		goto out;
 	}
-- 
2.25.0