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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1sE8uE-0000000EAgX-0enb; Mon, 03 Jun 2024 14:43:26 +0000 Date: Mon, 3 Jun 2024 15:43:26 +0100 From: Matthew Wilcox To: Lance Yang Cc: akpm@linux-foundation.org, ryan.roberts@arm.com, david@redhat.com, 21cnbao@gmail.com, baolin.wang@linux.alibaba.com, ziy@nvidia.com, fengwei.yin@intel.com, ying.huang@intel.com, libang.li@antgroup.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/1] mm/mlock: implement folio_mlock_step() using folio_pte_batch() Message-ID: References: <20240603140745.83880-1-ioworker0@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240603140745.83880-1-ioworker0@gmail.com> X-Stat-Signature: 1zj5hnuiehxopd43was48fr1rdoqcs3c X-Rspamd-Queue-Id: EB89120006 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1717425818-13732 X-HE-Meta: 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 eYUUnoZI vXarrCsE8YzKziOGzhbd85yyWLA0Rv0A+h4EGAEzNtJ/tl5bbdWDZOp3Qe/1uiJPA9xLK9ivg77EPVKCqXsvPv4YYMiDFCsQ/bF6VigwJpdC/LYZwnRuhjO5qnQJwtoHaMSvKHF6+O1r8L+RrHMc++sU7Jnm8CX1jZ2bAoJ6QH0jysacDdxeRM4wK28JA55peNIQRug+JJLhXwqiZpTrCKwaFXQ== 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: List-Subscribe: List-Unsubscribe: On Mon, Jun 03, 2024 at 10:07:45PM +0800, Lance Yang wrote: > +++ b/mm/mlock.c > @@ -307,26 +307,15 @@ void munlock_folio(struct folio *folio) > static inline unsigned int folio_mlock_step(struct folio *folio, > pte_t *pte, unsigned long addr, unsigned long end) > { > - unsigned int count, i, nr = folio_nr_pages(folio); > - unsigned long pfn = folio_pfn(folio); > + const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; > + unsigned int count = (end - addr) >> PAGE_SHIFT; This is a pre-existing bug, but ... what happens if you're on a 64-bit system and you mlock() a range that is exactly 2^44 bytes? Seems to me that count becomes 0. Why not use an unsigned long here and avoid the problem entirely? folio_pte_batch() also needs to take an unsigned long max_nr in that case, because you aren't restricting it to folio_nr_pages().