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[109.81.31.43]) by smtp.gmail.com with UTF8SMTPSA id 4fb4d7f45d1cf-62fa5f1389fsm10310583a12.27.2025.09.23.00.29.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Sep 2025 00:29:13 -0700 (PDT) Date: Tue, 23 Sep 2025 09:29:12 +0200 From: Michal Hocko To: Wei Yang Cc: akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, david@redhat.com, anshuman.khandual@arm.com, linux-mm@kvack.org, Oscar Salvador Subject: Re: [PATCH] mm/page_alloc: fix alignment for alloc_contig_pages_noprof() Message-ID: References: <20250923001943.2479-1-richard.weiyang@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250923001943.2479-1-richard.weiyang@gmail.com> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: CC4FC14000E X-Stat-Signature: ysxrhdiy9yuigqe41oyeu4fg9ohrmekj X-Rspam-User: X-HE-Tag: 1758612555-457239 X-HE-Meta: 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 O8v++qzo 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 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 Tue 23-09-25 00:19:43, Wei Yang wrote: > Commit 5e27a2df03b8 ("mm/page_alloc: add alloc_contig_pages()") > introduced generic method for alloc_contig_pages(). But the alignment > calculation seems wrong. > > Since ALIGN() only accept power of two value, while nr_pages could be > any positive one, the result is not defined. > > Use roundup() to calculate the correct alignment. What is the problem you are trying to fix here? The ALIGN is certainly not well defined for nr_pages that is not power of two but does any caller of alloc_contig_pages assumes any specific alignment, especially when nr_pages is not power of two? > Fixes: 5e27a2df03b8 ("mm/page_alloc: add alloc_contig_pages()") > Signed-off-by: Wei Yang > Cc: Anshuman Khandual > Cc: Oscar Salvador > Cc: Brendan Jackman > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Suren Baghdasaryan > Cc: Vlastimil Babka > Cc: Wei Yang > Cc: Zi Yan > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index a1bcc1e003c7..a17a6014e3db 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7095,7 +7095,7 @@ struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask, > gfp_zone(gfp_mask), nodemask) { > spin_lock_irqsave(&zone->lock, flags); > > - pfn = ALIGN(zone->zone_start_pfn, nr_pages); > + pfn = roundup(zone->zone_start_pfn, nr_pages); > while (zone_spans_last_pfn(zone, pfn, nr_pages)) { > if (pfn_range_valid_contig(pfn, nr_pages)) { > /* > -- > 2.34.1 -- Michal Hocko SUSE Labs