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[2003:cb:c708:f100:8096:9368:ba52:a341]) by smtp.gmail.com with ESMTPSA id p6-20020a05600c204600b003973d0a78casm2062244wmg.38.2022.05.31.06.02.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 31 May 2022 06:02:26 -0700 (PDT) Message-ID: <768fbb44-90c3-1f88-73a0-8765b2233226@redhat.com> Date: Tue, 31 May 2022 15:02:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH 3/3] mm/swapfile: fix possible data races of inuse_pages To: Miaohe Lin , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220527092626.31883-1-linmiaohe@huawei.com> <20220527092626.31883-4-linmiaohe@huawei.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20220527092626.31883-4-linmiaohe@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 378B6160046 X-Stat-Signature: kotzfk1kp3kkeack16tdxg5crfxtxba7 Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=cJy2m8Mf; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf08.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1654002129-358081 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 27.05.22 11:26, Miaohe Lin wrote: > si->inuse_pages could still be accessed concurrently now. The plain reads > outside si->lock critical section, i.e. swap_show and si_swapinfo, which > results in data races. But these should be ok because they're just used > for showing swap info. > > Signed-off-by: Miaohe Lin > --- > mm/swapfile.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index e033a53a99df..29d7ca9eaa3c 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -2649,7 +2649,7 @@ static int swap_show(struct seq_file *swap, void *v) > } > > bytes = si->pages << (PAGE_SHIFT - 10); > - inuse = si->inuse_pages << (PAGE_SHIFT - 10); > + inuse = READ_ONCE(si->inuse_pages) << (PAGE_SHIFT - 10); > > file = si->swap_file; > len = seq_file_path(swap, file, " \t\n\\"); > @@ -3268,7 +3268,7 @@ void si_swapinfo(struct sysinfo *val) > struct swap_info_struct *si = swap_info[type]; > > if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) > - nr_to_be_unused += si->inuse_pages; > + nr_to_be_unused += READ_ONCE(si->inuse_pages); > } > val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused; > val->totalswap = total_swap_pages + nr_to_be_unused; AFAIKT, this makes sense Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb