linux-kernel - [PATCH v2 49/61] mm/ksm: Use maple tree iterators instead of vma linked list

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Message-ID: <20210817154651.1570984-50-Liam.Howlett@oracle.com>
Date:   Tue, 17 Aug 2021 15:47:31 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>,
        Liam Howlett <liam.howlett@...cle.com>
Subject: [PATCH v2 49/61] mm/ksm: Use maple tree iterators instead of vma
 linked list

From: "Liam R. Howlett" <Liam.Howlett@...cle.com>

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/ksm.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 08092e6f0b73..1e2218a81bfc 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -975,11 +975,14 @@ static int unmerge_and_remove_all_rmap_items(void)
 						struct mm_slot, mm_list);
 	spin_unlock(&ksm_mmlist_lock);
 
-	for (mm_slot = ksm_scan.mm_slot;
-			mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) {
+	for (mm_slot = ksm_scan.mm_slot; mm_slot != &ksm_mm_head;
+	     mm_slot = ksm_scan.mm_slot) {
+		MA_STATE(mas, &mm_slot->mm->mm_mt, 0, 0);
+
 		mm = mm_slot->mm;
 		mmap_read_lock(mm);
-		for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		rcu_read_lock();
+		mas_for_each(&mas, vma, ULONG_MAX) {
 			if (ksm_test_exit(mm))
 				break;
 			if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
@@ -991,6 +994,7 @@ static int unmerge_and_remove_all_rmap_items(void)
 		}
 
 		remove_trailing_rmap_items(&mm_slot->rmap_list);
+		rcu_read_unlock();
 		mmap_read_unlock(mm);
 
 		spin_lock(&ksm_mmlist_lock);
@@ -1014,6 +1018,7 @@ static int unmerge_and_remove_all_rmap_items(void)
 	return 0;
 
 error:
+	rcu_read_unlock();
 	mmap_read_unlock(mm);
 	spin_lock(&ksm_mmlist_lock);
 	ksm_scan.mm_slot = &ksm_mm_head;
@@ -2228,6 +2233,7 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
 	struct vm_area_struct *vma;
 	struct rmap_item *rmap_item;
 	int nid;
+	MA_STATE(mas, NULL, 0, 0);
 
 	if (list_empty(&ksm_mm_head.mm_list))
 		return NULL;
@@ -2285,13 +2291,15 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
 	}
 
 	mm = slot->mm;
+	mas.tree = &mm->mm_mt;
+
 	mmap_read_lock(mm);
+	rcu_read_lock();
 	if (ksm_test_exit(mm))
-		vma = NULL;
-	else
-		vma = find_vma(mm, ksm_scan.address);
+		goto no_vmas;
 
-	for (; vma; vma = vma->vm_next) {
+	mas_set(&mas, ksm_scan.address);
+	mas_for_each(&mas, vma, ULONG_MAX) {
 		if (!(vma->vm_flags & VM_MERGEABLE))
 			continue;
 		if (ksm_scan.address < vma->vm_start)
@@ -2319,6 +2327,7 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
 					ksm_scan.address += PAGE_SIZE;
 				} else
 					put_page(*page);
+				rcu_read_unlock();
 				mmap_read_unlock(mm);
 				return rmap_item;
 			}
@@ -2329,6 +2338,7 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
 	}
 
 	if (ksm_test_exit(mm)) {
+no_vmas:
 		ksm_scan.address = 0;
 		ksm_scan.rmap_list = &slot->rmap_list;
 	}
@@ -2357,9 +2367,11 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
 
 		free_mm_slot(slot);
 		clear_bit(MMF_VM_MERGEABLE, &mm->flags);
+		rcu_read_unlock();
 		mmap_read_unlock(mm);
 		mmdrop(mm);
 	} else {
+		rcu_read_unlock();
 		mmap_read_unlock(mm);
 		/*
 		 * mmap_read_unlock(mm) first because after
-- 
2.30.2