Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <1cbc8768-7a94-530d-f3ba-923038e6ef12@gmail.com>
Date:   Fri, 2 Jun 2023 13:38:44 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.11.0
Content-Language: en-US
From:   "Colin King (gmail)" <colin.i.king@gmail.com>
Subject: re: zswap: do not shrink if cgroup may not zswap
To:     Nhat Pham <nphamcs@gmail.com>, Seth Jennings <sjenning@redhat.com>,
        Dan Streetman <ddstreet@ieee.org>,
        Vitaly Wool <vitaly.wool@konsulko.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Linux-MM <linux-mm@kvack.org>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi,

static analysis with clang scan build has detected an issue in the 
following commit:

commit 6804144bf1cfa3978ad98e625d8a1d2a4b80cbee
Author: Nhat Pham <nphamcs@gmail.com>
Date:   Tue May 30 15:24:40 2023 -0700

     zswap: do not shrink if cgroup may not zswap


The issue is as follows in function zswap_frontswap_store in mm/zswap.c:

         /*
          * XXX: zswap reclaim does not work with cgroups yet. Without a
          * cgroup-aware entry LRU, we will push out entries system-wide 
based on
          * local cgroup limits.
          */
         objcg = get_obj_cgroup_from_page(page);
         if (objcg && !obj_cgroup_may_zswap(objcg))
                 goto reject;

mm/zswap.c:1210:6: warning: variable 'ret' is used uninitialized 
whenever 'if' condition is true [-Wsometimes-uninitialized]

The goto reject path ends up returning ret, however, ret at this point 
has not been initialized, so a garbage return value is being returned
by function zswap_frontswap_store

Colin