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[209.85.220.73]) by mx.google.com with SMTPS id n9sor49356620pgl.53.2019.08.01.18.53.37 for (Google Transport Security); Thu, 01 Aug 2019 18:53:37 -0700 (PDT) Received-SPF: pass (google.com: domain of 3ojddxqokcm00x6ahuda6bz77z4x.v75416dg-553etv3.7az@flex--henryburns.bounces.google.com designates 209.85.220.73 as permitted sender) client-ip=209.85.220.73; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=ljI7lFF3; spf=pass (google.com: domain of 3ojddxqokcm00x6ahuda6bz77z4x.v75416dg-553etv3.7az@flex--henryburns.bounces.google.com designates 209.85.220.73 as permitted sender) smtp.mailfrom=3oJdDXQoKCM00x6AHuDA6Bz77z4x.v75416DG-553Etv3.7Az@flex--henryburns.bounces.google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=VKzEuSkmyrWV8LhwIH3JFAo5TpB9gh8PzM9j2uJXmIA=; b=ljI7lFF3O1uGnDJgLjRw0nWAvDTSYyuHT002SegNqoGSSb9OLyCXLW4bvQwWX+qe6V V8wJyCYEPbFnkif6rt8y681avtdd4OXMPubBiEaIx1Lnxy6Lk4ro3uR/f0txJInnuZ0M yX2RYvNbUC3w9m+LKYUPbcjYgI+2S4RRgGV7dSs1rDRHmfuvkjs3QRY5Nom+99Lvujqy RVIFe5Kp3hVYnZpoOnuzgjOxx+c/yhMqr7N4KhLSFDHkeelY9Dec413o9Wt3oqVtk2ZU c8kH6QeWOT6aag7/h4j+Lzfi5RMbgcZlAgILtJrvzfZm0aWW409BAvH+WhXeRAiyeeoi zuTA== X-Google-Smtp-Source: APXvYqzcvYNu3kUvzm7uEj+DWVq5JRNiJA6B1G5NwHfF9cgJ8y3vPHN7XgvR2puOfpuYvp6BotAWHMYLYz5iAEeA X-Received: by 2002:a63:f807:: with SMTP id n7mr125813928pgh.119.1564710816388; Thu, 01 Aug 2019 18:53:36 -0700 (PDT) Date: Thu, 1 Aug 2019 18:53:31 -0700 Message-Id: <20190802015332.229322-1-henryburns@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.22.0.770.g0f2c4a37fd-goog Subject: [PATCH 1/2] mm/zsmalloc.c: Migration can leave pages in ZS_EMPTY indefinitely From: Henry Burns To: Minchan Kim , Nitin Gupta Cc: Sergey Senozhatsky , Shakeel Butt , Jonathan Adams , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Henry Burns Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: In zs_page_migrate() we call putback_zspage() after we have finished migrating all pages in this zspage. However, the return value is ignored. If a zs_free() races in between zs_page_isolate() and zs_page_migrate(), freeing the last object in the zspage, putback_zspage() will leave the page in ZS_EMPTY for potentially an unbounded amount of time. To fix this, we need to do the same thing as zs_page_putback() does: schedule free_work to occur. To avoid duplicated code, move the sequence to a new putback_zspage_deferred() function which both zs_page_migrate() and zs_page_putback() call. Signed-off-by: Henry Burns --- mm/zsmalloc.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 1cda3fe0c2d9..efa660a87787 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1901,6 +1901,22 @@ static void dec_zspage_isolation(struct zspage *zspage) zspage->isolated--; } +static void putback_zspage_deferred(struct zs_pool *pool, + struct size_class *class, + struct zspage *zspage) +{ + enum fullness_group fg; + + fg = putback_zspage(class, zspage); + /* + * Due to page_lock, we cannot free zspage immediately + * so let's defer. + */ + if (fg == ZS_EMPTY) + schedule_work(&pool->free_work); + +} + static void replace_sub_page(struct size_class *class, struct zspage *zspage, struct page *newpage, struct page *oldpage) { @@ -2070,7 +2086,7 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage, * the list if @page is final isolated subpage in the zspage. */ if (!is_zspage_isolated(zspage)) - putback_zspage(class, zspage); + putback_zspage_deferred(pool, class, zspage); reset_page(page); put_page(page); @@ -2115,15 +2131,9 @@ static void zs_page_putback(struct page *page) spin_lock(&class->lock); dec_zspage_isolation(zspage); - if (!is_zspage_isolated(zspage)) { - fg = putback_zspage(class, zspage); - /* - * Due to page_lock, we cannot free zspage immediately - * so let's defer. - */ - if (fg == ZS_EMPTY) - schedule_work(&pool->free_work); - } + if (!is_zspage_isolated(zspage)) + putback_zspage_deferred(pool, class, zspage); + spin_unlock(&class->lock); } -- 2.22.0.770.g0f2c4a37fd-goog