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Thu, 18 Dec 2025 07:47:44 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id fLIwLqCxQ2nnCwAAD6G6ig (envelope-from ); Thu, 18 Dec 2025 07:47:44 +0000 Message-ID: <7b2673cb-1f0e-4a5a-84e3-0ae10437308d@suse.cz> Date: Thu, 18 Dec 2025 08:47:44 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] introduce pagetable_alloc_nolock() To: Brendan Jackman , Yeoreum Yun , Ryan Roberts Cc: akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, hannes@cmpxchg.org, ziy@nvidia.com, bigeasy@linutronix.de, clrkwllms@kernel.org, rostedt@goodmis.org, catalin.marinas@arm.com, will@kernel.org, kevin.brodsky@arm.com, dev.jain@arm.com, yang@os.amperecomputing.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-arm-kernel@lists.infradead.org References: <20251212161832.2067134-1-yeoreum.yun@arm.com> <916c17ba-22b1-456e-a184-cb3f60249af7@arm.com> <100cc8da-b826-4fc2-a624-746bf6fb049d@arm.com> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: EB2C6160015 X-Stat-Signature: tm4g7rnhpra6it6epgkoakc4sprjkgcd X-Rspam-User: X-HE-Tag: 1766044066-620779 X-HE-Meta: U2FsdGVkX1+mIiHDWC4oKzznausa4+zuPn2bBnblnZJNiKY8Cf59lZZwRpS/GGUQeD7C0LX/ggzYPmJ40fd27/CSCaqYMR3jE5e9yllLq5R+Race80qVypqkvhGLjUHxTOTU4Du1PJ580K0y4ezLGvQMJZ15bni9g018mC807d62HvmXaR+JI6FxmEJemPPk+9Gh0wY2UY2igXSdtqv993h07nJAAz7aH+alo0KYrWWEdKKess1kKU2h9R68p/5xymd+DwmK0+MLkDCVSraWhTMIfX5os0XSLbPP6GNVPfL5T631L8offxUL9GwRBwhFvFCiGo6cHrqCNMpfsPDEWUocrSyFi3oJwpq4Ej2y4eEqEAVYpeBfA5lNz6jGW1DdqbCAKB8o3ze3GcJUpjdp0ZhyEC6xPBSE5nn0zec/KjEBFiVAimeXNneNg+cYuMYUsp6YUt7crYmHOHrFt6VHEm4MW6m+cv1g4vQIWDIHFypBSEBrKO4kYzcT5KX2msxJ8Urod57gp1w1DaCcXSVTyTO6xLG7buGoS3INOODWTitews54HU/ws8RESwA+Yu1Ppo7OdWZ1g7D4FZ8ue0011vWRaRUznYK6W0NaayVz0tzwABbWmh8vp5+lejfT0ohhOx56qE5Vx6oUIDX0Sp/vQHmd2prcVrol7G8jJZWQHWuWwvcUgXr/Hfe30y4UOxQc3EMLowqlUur4F188khVc6n9Zw0ZEw8Z8szqxBrlKb+C4zbhWWip1MDCDyG1hV/F4/Mc7SxOFZr1/u7YDVk6y/SDas79l+FoM6MH/TRtHS8j0Gmke/WjdfzPBrxHGSb+5DErHuVkArP7GxVM54XN3WwMNaGKxwDRS6ThFAPMFZS7NMoZakFRFxDzFaxse0JEWnebhXAbXl7VW72V+5t2vIttbPcfz+R9CNtYMl8CoCpVpbh/P01LumKPCdRPWSr/z0M8umlLbz+NIXBvLEJX AOcp6Ezq +KMWX4FGUqOEU3shQCzt+JNJJWfua+6sLix+jl37Yp9SqE64iGljE6ypBtv84iM2TE2FBpvMot5YxsS3k337rSaqLYnM08QbJw9/7aAQfb5VAvDZeuq/jN+cnZVRlUDkfA8WGh/FGi/qlC4vR2BKB1cYNOnJliylwau06Na0m2/cZ3zvxk9qE5dAMm8/AbXUQeKP1VCHSGJsuw3gomKberLXXfG4d2H6S6qsGM6U5TRoNieS8/A2m4hEPMHQ9esTZnotmitmqk4Xkb+l1Hg8/pVht71iChz3RGRj48KOFPvBPHp5bRaIU0O+kQGazuIDpDzgAqGMPNGvyppqvUJQTHCD8dzhiMHjokXjbbJks75nadkgAa1CxjGo/SJ4isXO8cCTOAcUqaaPzna10eTDXR8YQ328Q9NsZd4AstbCYpxIF4vQ= 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 12/17/25 18:19, Brendan Jackman wrote: >>> From 4c6b4d4cb08aee9559d02a348b9ecf799142c96f Mon Sep 17 00:00:00 2001 >>> From: Brendan Jackman >>> Date: Wed, 17 Dec 2025 13:26:28 +0000 >>> Subject: [PATCH] mm: clarify GFP_ATOMIC/GFP_NOWAIT doc-comment >>> >>> The current description of contexts where it's invalid to make >>> GFP_ATOMIC and GFP_NOWAIT calls is rather vague. >>> >>> Replace this with a direct description of the actual contexts of concern >>> and refer to the RT docs where this is explained more discursively. >>> >>> While rejigging this prose, also move the documentation of GFP_NOWAIT to >>> the GFP_NOWAIT section. >> >> There doesn't seem to be any move? > > This is referring to [0] and [1]. Oh I missed [0]. Thanks! >>> diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h >>> index 3de43b12209ee..07a378542caf2 100644 >>> --- a/include/linux/gfp_types.h >>> +++ b/include/linux/gfp_types.h >>> @@ -309,8 +309,10 @@ enum { >>> * >>> * %GFP_ATOMIC users can not sleep and need the allocation to succeed. A lower >>> * watermark is applied to allow access to "atomic reserves". >>> - * The current implementation doesn't support NMI and few other strict >>> - * non-preemptive contexts (e.g. raw_spin_lock). The same applies to %GFP_NOWAIT. > [0] ^^^^^^^^^^^^^^^^^^^^^^^^^^ >>> + * The current implementation doesn't support NMI, nor contexts that disable >>> + * preemption under PREEMPT_RT. This includes raw_spin_lock() and plain >>> + * preempt_disable() - see Documentation/core-api/real-time/differences.rst for >>> + * more info. >> >> Can we reference the "Memory allocation" section directly? > > Yeah good point. I will send this as a standalone [PATCH] mail tomorrow. > >>> * >>> * %GFP_KERNEL is typical for kernel-internal allocations. The caller requires >>> * %ZONE_NORMAL or a lower zone for direct access but can direct reclaim. >>> @@ -321,6 +323,7 @@ enum { >>> * %GFP_NOWAIT is for kernel allocations that should not stall for direct >>> * reclaim, start physical IO or use any filesystem callback. It is very >>> * likely to fail to allocate memory, even for very small allocations. >>> + * The same restrictions on calling contexts apply as for %GFP_ATOMIC. > [1] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >