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From: Naoya Horiguchi To: Miaohe Lin Cc: akpm@linux-foundation.org, naoya.horiguchi@nec.com, shy828301@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] mm: memory-failure: fix potential unexpected return value from unpoison_memory() Message-ID: <20230719234851.GA1583723@ik1-406-35019.vs.sakura.ne.jp> References: <20230715031729.2420338-1-linmiaohe@huawei.com> <20230715031729.2420338-3-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230715031729.2420338-3-linmiaohe@huawei.com> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3D8824000C X-Stat-Signature: shohxzt1f7hu8c5t5ubsktpwnucwbeon X-HE-Tag: 1689810540-355681 X-HE-Meta: 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 3kgUlmy8 jTYmWqPIYHgwWnKUKzqbMj3SbYLKT5GLaLNIE+HuO45+5hvRWOB5gncrPCk/MgIZIc4Qe4eTsz9sHA+J1gNpYyiOQmsbIUaY+L+WCF/PiRt3i319wnqWUPnDjAA== 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 Sat, Jul 15, 2023 at 11:17:27AM +0800, Miaohe Lin wrote: > If unpoison_memory() fails to clear page hwpoisoned flag, return value > ret is expected to be -EBUSY. But when get_hwpoison_page() returns 1 > and fails to clear page hwpoisoned flag due to races, return value will > be unexpected 1 leading to users being confused. Thank you for fixing this. > > Fixes: bf181c582588 ("mm/hwpoison: fix unpoison_memory()") > Signed-off-by: Miaohe Lin > --- > mm/memory-failure.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 9ab97016877e..ac074f82f5b3 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -2546,11 +2546,11 @@ int unpoison_memory(unsigned long pfn) > unpoison_pr_info("Unpoison: failed to grab page %#lx\n", > pfn, &unpoison_rs); > } else { > + ret = -EBUSY; It seems be a code smell to me that the variable "ret" is used not only to save the return value of unpoison_memory(), but also to save the return value from get_hwpoison_page(). So I think that it might be better to use another auto-variable solely to save the return value of get_hwpoison_page. Then ret has the initial value -EBUSY at this point and no need to reinitialize it. Thanks, Naoya Horiguchi > if (PageHuge(p)) { > huge = true; > count = folio_free_raw_hwp(folio, false); > if (count == 0) { > - ret = -EBUSY; > folio_put(folio); > goto unlock_mutex; > } > -- > 2.33.0 > > >