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Tue, 14 Sep 2021 13:09:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id KhKJDBafQGGJRAAAMHmgww (envelope-from ); Tue, 14 Sep 2021 13:09:42 +0000 Message-ID: <6d27e47b-66da-4a51-fa16-056e3ab2eedf@suse.cz> Date: Tue, 14 Sep 2021 15:09:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [PATCH v3] mm/page_isolation: guard against possible putback unisolated page Content-Language: en-US To: Miaohe Lin , akpm@linux-foundation.org Cc: david@redhat.com, jhubbard@nvidia.com, iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210914114508.23725-1-linmiaohe@huawei.com> From: Vlastimil Babka In-Reply-To: <20210914114508.23725-1-linmiaohe@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 7358D801A89F X-Stat-Signature: e3w7ri8sgjnoxerjz7zp18566jizr967 Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=mn6W7skU; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=1XRMyWMK; spf=pass (imf06.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-HE-Tag: 1631624983-592692 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 9/14/21 13:45, Miaohe Lin wrote: > Isolating a free page in an isolated pageblock is expected to always work > as watermarks don't apply here. But if __isolate_free_page() failed, due > to condition changes, the page will be left on the free list. And the page > will be put back to free list again via __putback_isolated_page(). This may > trigger VM_BUG_ON_PAGE() on page->flags checking in __free_one_page() if > PageReported is set. Or we will corrupt the free list because list_add() > will be called for pages already on another list. Add a VM_WARN_ON() to > complain about this change. > > Signed-off-by: Miaohe Lin Acked-by: Vlastimil Babka > --- > v1->v2: > Add VM_WARN_ON to catch unexpected isolating failure. > v2->v3: > Change the patch description+subject and remove Fixes. > --- > mm/page_isolation.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index f93cc63d8fa1..f67c4c70f17f 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -94,8 +94,13 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) > buddy = page + (buddy_pfn - pfn); > > if (!is_migrate_isolate_page(buddy)) { > - __isolate_free_page(page, order); > - isolated_page = true; > + isolated_page = !!__isolate_free_page(page, order); > + /* > + * Isolating a free page in an isolated pageblock > + * is expected to always work as watermarks don't > + * apply here. > + */ > + VM_WARN_ON(!isolated_page); > } > } > } >