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b=qzMBJqJ/CkX22YMjxInR8KPOs1WydZlWfE3u04qA4qRQGBtS9ORp5ykmHbbMD+FT5 iRvB+omVod31Eh1004YiGlNXtSQmilLRUmjU7eyEhHFDNmJ1jmKH80omHTUeAiC3TM UpKmMIMRnqb5VHDNcLDlFJ0l0gqZoA6Qg5B6EmoAlWFNq3txMOKX35KeyaIj1Ff0MC Mkc45NpQ7TeXi9npg5eZhMbVpxDBDhF4LQLwaYG7ICwptEIo6zG7H+sgI0v0+QFzjp E13QV27r4xwT4/IX0t2efZo5zUTPOcPKoeKFdrtAoAHqOvC7DFkQdDDm2vKet1EFmG dlLyBt/5fqwbQ== Date: Tue, 10 Mar 2026 07:56:54 +0000 From: "Lorenzo Stoakes (Oracle)" To: Dev Jain Cc: akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, david@kernel.org, hughd@google.com, chrisl@kernel.org, kasong@tencent.com, weixugc@google.com, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, pfalcato@suse.de, baolin.wang@linux.alibaba.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, baohua@kernel.org, youngjun.park@lge.com, ziy@nvidia.com, kas@kernel.org, willy@infradead.org, yuzhao@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com Subject: Re: [PATCH 1/9] mm/rmap: make nr_pages signed in try_to_unmap_one Message-ID: <21801fb7-0f42-4ad3-8b85-2ac6013b8aa5@lucifer.local> References: <20260310073013.4069309-1-dev.jain@arm.com> <20260310073013.4069309-2-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260310073013.4069309-2-dev.jain@arm.com> X-Rspam-User: X-Stat-Signature: 3atryd6ncscxc3yhraaqnc6h5if9pg5n X-Rspamd-Queue-Id: 2399B1C0002 X-Rspamd-Server: rspam03 X-HE-Tag: 1773129426-191759 X-HE-Meta: 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 N67EylNA FGvOa8qW1AR6xuS0Os4we87uKCUI9r26Kcjce5qT7HC2ML/jBMb7lgPP1VukCQNv9Idb08N/WuMmy5aCwln3LzbcJ0sGDA1PBj+RiHvRNf7v65QReiGxjkDtPXIxOZdJWxKQdo3DfPX37bZX99OTOwJkTTjM+5exbym6Nk/z/xNuzMM6EPEGOZnh4QyTMQ27KpV2kBQ/I/a7ElFZuCGipmrd1ecuPAwYTeHgQC+f1BlfJlhJcgejhNAex+EhEmi+I4saJn6TMKvAHlLTA1u30uhRvlxac2MhRZSqEQhFIYRF0rPcPFNdyrV4MWj/TF/REqsdv Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 10, 2026 at 01:00:05PM +0530, Dev Jain wrote: > Currently, nr_pages is defined as unsigned long. We use nr_pages to > manipulate mm rss counters for lazyfree folios as follows: > > add_mm_counter(mm, MM_ANONPAGES, -nr_pages); > > Suppose nr_pages = 3. -nr_pages underflows and becomes ULONG_MAX - 2. Then, > since add_mm_counter() uses this -nr_pages as a long, ULONG_MAX - 2 does > not fit into the positive range of long, and is converted to -3. Eventually > all of this works out, but for keeping things simple, declare nr_pages as > a signed variable. > > Signed-off-by: Dev Jain > --- > mm/rmap.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/rmap.c b/mm/rmap.c > index 6398d7eef393f..087c9f5b884fe 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1979,9 +1979,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > struct page *subpage; > struct mmu_notifier_range range; > enum ttu_flags flags = (enum ttu_flags)(long)arg; > - unsigned long nr_pages = 1, end_addr; > + unsigned long end_addr; > unsigned long pfn; > unsigned long hsz = 0; > + long nr_pages = 1; This is a non-issue that makes the code confusing, so let's not? The convention throughout the kernel is nr_pages generally is unsigned because you can't have negative nr_pages. > int ptes = 0; > > /* > -- > 2.34.1 >