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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ltl8ImxL; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B2304606A321; Thu, 12 Nov 2026 08:54:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ltl8ImxL Received: by smtp.kernel.org (Postfix) with ESMTPSA id 960071F00A07; Thu, 12 Nov 2026 08:54:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794473650; bh=ePkuZsGQpV9jd5TnZXMBz49Rl2IFx60CuIIApPV/Lyo=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ltl8ImxLoafNcK4EpGTLoPNj5qUQQrLzABRGpWQsvGY1mDdlI6VDdtd1H+ts2pVCP UNaUiMIS/ZiSZgav9R3+NQ1QnEtCSbRGPylnH7/84HLfeIRwjHIFRibRbkph5z7FuR 7nHX/Ao5Rs/JC/8dPC/017P7gQXwZynLSf4GRDiI2bAe6oL1Zq8t0B2mPfTMDBP2M7 gH//ZjoWG10PI/DHwgsfFRMxTon52cjOWoiBXQdqw9hNFA1pWXkrjzv9VatUuAq+Xg 3nEhT64qFWQwD2QU2V5srpExAnV6DtqecgNhn9pIH/DIfY8s/uIrpk9pkJzL18YYwC RJoqAbZOaCdWA== Message-ID: Date: Thu, 12 Nov 2026 09:49:11 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/3] mm: gup: allow long-term pins of CMA-allocated HugeTLB folios To: Qi Zheng , Muchun Song Cc: osalvador@suse.de, akpm@linux-foundation.org, azpijr@gmail.com, Lance Yang , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Qi Zheng References: <503c9f6d869e3206c6fd591de962c3d619b73825.1794379433.git.zhengqi.arch@bytedance.com> <80FED512-77D2-4D49-BAE5-745CE1F711CA@linux.dev> <1116fd15-a927-4f6e-a0ab-084bc36a90aa@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 11/12/26 07:13, Qi Zheng wrote: > > > On 11/11/26 3:42 PM, Muchun Song wrote: >> >> >>> >>> From: Qi Zheng >>> >>> Long-term pinning treats explicitly CMA-allocated HugeTLB folios as >>> unpinnable, causing unnecessary migration or pinning failures. >>> >>> These folios already own their CMA bitmap ranges, and memory blocks >> >> Commit message needs updating to bitmap as well. > > Will do. > >> >>> overlapping CMA areas cannot be offlined. Allow HugeTLB folios with >>> HPG_cma to be pinned directly, including in ZONE_MOVABLE. >>> >>> Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages >>> using cma") >>> Cc: stable@vger.kernel.org >>> Suggested-by: Muchun Song >>> Signed-off-by: Qi Zheng >>> Acked-by: Muchun Song >>> Reviewed-by: Oscar Salvador >>> Reviewed-by: Jose A. Perez de Azpillaga >>> --- >>> include/linux/mm.h | 29 +---------------------------- >>> mm/gup.c           | 31 +++++++++++++++++++++++++++++++ >>> 2 files changed, 32 insertions(+), 28 deletions(-) >>> >>> diff --git a/include/linux/mm.h b/include/linux/mm.h >>> index b0da9be413098..47d1d96bfc7fd 100644 >>> --- a/include/linux/mm.h >>> +++ b/include/linux/mm.h >>> @@ -2954,35 +2954,8 @@ static inline bool is_zero_folio(const struct folio >>> *folio) >>>     return is_zero_page(&folio->page); >>> } >>> >>> -/* MIGRATE_CMA and ZONE_MOVABLE do not allow pin folios */ >>> #ifdef CONFIG_MIGRATION >>> -static inline bool folio_is_longterm_pinnable(struct folio *folio) >> >> I think David prefer to move this function first, then fix it in a separate >> patch, >> right? > > Hi David, is this what you mean? If so, I will split it into two patches > for the v5. Let's try something that is more future-directed: cma should deal with cma details. In the future we might implement something reasonable there. diff --git a/include/linux/cma.h b/include/linux/cma.h index 8555d38a97b1a..d829fd0355bae 100644 --- a/include/linux/cma.h +++ b/include/linux/cma.h @@ -21,6 +21,9 @@ #define CMA_MIN_ALIGNMENT_BYTES (PAGE_SIZE * CMA_MIN_ALIGNMENT_PAGES) struct cma; +struct folio; + +bool cma_folio_is_longterm_pinnable(struct folio *folio); extern unsigned long totalcma_pages; extern phys_addr_t cma_get_base(const struct cma *cma); diff --git a/include/linux/mm.h b/include/linux/mm.h index 6af3b7008f1ad..5392e225cab9b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3,6 +3,7 @@ #define _LINUX_MM_H #include +#include #include #include #include @@ -2975,7 +2976,10 @@ static inline bool is_zero_folio(const struct folio *folio) return is_zero_page(&folio->page); } -/* MIGRATE_CMA and ZONE_MOVABLE do not allow pin folios */ +/* + * MIGRATE_CMA and ZONE_MOVABLE folios cannot normally be long-term pinned. + * CMA may allow pinning folios explicitly allocated from its areas. + */ #ifdef CONFIG_MIGRATION static inline bool folio_is_longterm_pinnable(struct folio *folio) { @@ -2983,7 +2987,7 @@ static inline bool folio_is_longterm_pinnable(struct folio *folio) int mt = folio_migratetype(folio); if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE) - return false; + return cma_folio_is_longterm_pinnable(folio); #endif /* The zero page can be "pinned" but gets special handling. */ if (is_zero_folio(folio)) diff --git a/mm/cma.c b/mm/cma.c index 9ec1d1fd5dff5..b3bf0014a90f5 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -38,6 +39,16 @@ struct cma cma_areas[MAX_CMA_AREAS]; unsigned int cma_area_count; +bool cma_folio_is_longterm_pinnable(struct folio *folio) +{ + /* + * Explicitly allocated CMA folios own their bitmap ranges and can be + * pinned even in ZONE_MOVABLE, as CMA memory cannot be offlined. + * For now, only HugeTLB tracks these allocations with a folio flag. + */ + return folio_test_hugetlb(folio) && folio_test_hugetlb_cma(folio); +} + phys_addr_t cma_get_base(const struct cma *cma) { WARN_ON_ONCE(cma->nranges != 1); -- 2.43.0 In a follow-up cleanup folio_is_longterm_pinnable() can be moved to gup.c. -- Cheers, David