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Shutemov" To: Vlastimil Babka Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Qian Cai , "Kirill A. Shutemov" , Matthew Wilcox , Mel Gorman , Michal Hocko Subject: Re: [PATCH 1/3] mm, page_owner: fix off-by-one error in __set_page_owner_handle() Message-ID: <20190926090935.ofbyb2sjhi33nfp3@box> References: <20190925143056.25853-1-vbabka@suse.cz> <20190925143056.25853-2-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190925143056.25853-2-vbabka@suse.cz> User-Agent: NeoMutt/20180716 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 Wed, Sep 25, 2019 at 04:30:50PM +0200, Vlastimil Babka wrote: > As noted by Kirill, commit 7e2f2a0cd17c ("mm, page_owner: record page owner for > each subpage") has introduced an off-by-one error in __set_page_owner_handle() > when looking up page_ext for subpages. As a result, the head page page_owner > info is set twice, while for the last tail page, it's not set at all. > > Fix this and also make the code more efficient by advancing the page_ext > pointer we already have, instead of calling lookup_page_ext() for each subpage. > Since the full size of struct page_ext is not known at compile time, we can't > use a simple page_ext++ statement, so introduce a page_ext_next() inline > function for that. > > Reported-by: Kirill A. Shutemov > Fixes: 7e2f2a0cd17c ("mm, page_owner: record page owner for each subpage") > Signed-off-by: Vlastimil Babka Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov