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From:   Andrew Yang <andrew.yang@mediatek.com>
To:     Minchan Kim <minchan@kernel.org>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
CC:     <wsd_upstream@mediatek.com>, <casper.li@mediatek.com>,
        Andrew Yang <andrew.yang@mediatek.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>
Subject: [PATCH] zsmalloc: Fix races between modifications of fullness and isolated
Date:   Fri, 21 Jul 2023 14:37:01 +0800
Message-ID: <20230721063705.11455-1-andrew.yang@mediatek.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Since fullness and isolated share the same unsigned int,
modifications of them should be protected by the same lock.

Signed-off-by: Andrew Yang <andrew.yang@mediatek.com>
Fixes: c4549b871102 ("zsmalloc: remove zspage isolation for migration")
---
 mm/zsmalloc.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 32f5bc4074df..b96230402a8d 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1777,6 +1777,7 @@ static void replace_sub_page(struct size_class *class, struct zspage *zspage,
 
 static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
 {
+	struct zs_pool *pool;
 	struct zspage *zspage;
 
 	/*
@@ -1786,9 +1787,10 @@ static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
 	VM_BUG_ON_PAGE(PageIsolated(page), page);
 
 	zspage = get_zspage(page);
-	migrate_write_lock(zspage);
+	pool = zspage->pool;
+	spin_lock(&pool->lock);
 	inc_zspage_isolation(zspage);
-	migrate_write_unlock(zspage);
+	spin_unlock(&pool->lock);
 
 	return true;
 }
@@ -1858,8 +1860,8 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
 	 * Since we complete the data copy and set up new zspage structure,
 	 * it's okay to release the pool's lock.
 	 */
-	spin_unlock(&pool->lock);
 	dec_zspage_isolation(zspage);
+	spin_unlock(&pool->lock);
 	migrate_write_unlock(zspage);
 
 	get_page(newpage);
@@ -1876,14 +1878,16 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
 
 static void zs_page_putback(struct page *page)
 {
+	struct zs_pool *pool;
 	struct zspage *zspage;
 
 	VM_BUG_ON_PAGE(!PageIsolated(page), page);
 
 	zspage = get_zspage(page);
-	migrate_write_lock(zspage);
+	pool = zspage->pool;
+	spin_lock(&pool->lock);
 	dec_zspage_isolation(zspage);
-	migrate_write_unlock(zspage);
+	spin_unlock(&pool->lock);
 }
 
 static const struct movable_operations zsmalloc_mops = {
-- 
2.18.0