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h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FNOpvnT2UnIDLx7xLrJ9QrwaaYb4fg3fyxTc0TEQRFOMlUvuNl+1e8Ny4+tSZcY5P 7Xhzadyb/ODwynFJNTOFnI7gXLtYxd9vb+KM5pMPk/g1MWqS+8I+7rx2MpEaX/BN7e O0UOeItO/ucZDQBINLlsJiv+AC75tqqWDSlu9kj8= Date: Wed, 29 Apr 2026 15:42:24 +0100 From: Catalin Marinas To: Dev Jain Cc: akpm@linux-foundation.org, david@kernel.org, urezki@gmail.com, kees@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, arnd@arndb.de, Muhammad Usama Anjum , ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, tglx@kernel.org, mathieu.desnoyers@efficios.com, linux-arch@vger.kernel.org, ryan.roberts@arm.com Subject: Re: [PATCH v4 1/3] vmalloc: add __GFP_SKIP_KASAN support Message-ID: References: <20260429102704.680174-1-dev.jain@arm.com> <20260429102704.680174-2-dev.jain@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260429102704.680174-2-dev.jain@arm.com> X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6655F100016 X-Stat-Signature: mj3j689dc4mi7zzu8yh183xzdnhmt99x X-HE-Tag: 1777473761-802513 X-HE-Meta: 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 ZTGP/XnO 7ENsBmYxOfh5k396zIIl60sNoltjv0DsVS6rLCkYiNeaYSkn8SqnN0u1XUUILoimYMRKQC38bAof86iSOO6yXAXGz2Qv3BFmiuVm1eCwjAiCvc6dvCdaBV/QRFYeF4yv6K73cRSoVxonP2qu0mC88R9O7FWEsOhXdAIeyxYL7M8kmX4MqFnBg69JhrfvoAZmqci7XssWXcgZBCY7Yd+0ZIWELPgDd9h1dt9mfspXf3cwajU8v7RxefonMgBn2bHavwmntzCVIQK47iHBNQEmdBLNL0Ne1y3LViK+Sfr4jNFlQbIRjniZtko0BCEuKcxdoVWGTUURE0GBOUmMsBW4NF7AZUGjY8Ft9tQoAcThAqDc+Jfv2YZcnEpHYew== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 29, 2026 at 03:57:02PM +0530, Dev Jain wrote: > From: Muhammad Usama Anjum > > For allocations that will be accessed only with match-all pointers > (e.g., kernel stacks), setting tags is wasted work. If the caller > already set __GFP_SKIP_KASAN, skip tag setting of vmalloc pages. > > Before this patch, __GFP_SKIP_KASAN wasn't being used with vmalloc > APIs. So it wasn't being checked. Now its being checked and acted > upon. Other KASAN modes are unchanged because __GFP_SKIP_KASAN is > ignored for them in the page allocator, and in vmalloc too we ignore > this flag for them. > > This is a preparatory patch for optimizing kernel stack allocations. > > Signed-off-by: Muhammad Usama Anjum > Co-developed-by: Ryan Roberts > Signed-off-by: Ryan Roberts > Co-developed-by: Dev Jain > Signed-off-by: Dev Jain > --- > include/linux/gfp_types.h | 6 +++--- > mm/vmalloc.c | 13 +++++++++---- > 2 files changed, 12 insertions(+), 7 deletions(-) > > diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h > index 6c75df30a281d..c2bd723c8ec62 100644 > --- a/include/linux/gfp_types.h > +++ b/include/linux/gfp_types.h > @@ -281,9 +281,9 @@ enum { > * > * %__GFP_SKIP_KASAN makes KASAN skip unpoisoning on page allocation. > * Used for userspace and vmalloc pages; the latter are unpoisoned by > - * kasan_unpoison_vmalloc instead. For userspace pages, results in > - * poisoning being skipped as well, see should_skip_kasan_poison for > - * details. Only effective in HW_TAGS mode. > + * kasan_unpoison_vmalloc instead. If passed to vmalloc, kasan_unpoison_vmalloc > + * is skipped too. For userspace pages, results in poisoning being skipped as > + * well, see should_skip_kasan_poison for details. Only effective in HW_TAGS mode. Nit: keep the comment line length to less than 80, ideally close to the comments above (for esthetic reasons). Reviewed-by: Catalin Marinas