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AJvYcCWt+DS1c8mBFr0qwX4qW7U8RuhGBsvtD9XTBYkeoox3hppbetS6Pp7F/ywT9XFgpi/9TeEBWFstzg==@kvack.org X-Gm-Message-State: AOJu0YxAvU7VZ6iZnxTcnPTo9NbX8demTXgLy62b5/tbsi5cAfXvMG5S yPobJXp6M7yk+M00FCvIFOSON97MLHSfLknZ9F7tgF5mp16ue2uI3/9kvvFKqlz8LA9q2YB0Wey 5qAPt2gsZlGoiPEysuqZ53ePStaunjXH1lG3QwXwp X-Gm-Gg: ATEYQzz9e9DkBlMCKUjLU2VHK8ppSPHH7rGNbpyJNojtKfFf6bIzP+hRFbDqO0ZX1Mn atiI16PhKtVfZpVSovfmL0TlPSsSbWZR1fran8JdUOlThEf1VexVbkgP+XDhlitlxtjgy61mk+2 eN2y8lnWXS2P7liNxVw/Bei8Vfmv9CBz87fWoZasMZgcOuul9n/MLmTeQx/pMX780fKYktqKAWM wdAhn22ll/qXw5StIN3FlXkbW9DJq+uIPu9vgaDBfYDmNysQZNQrDl8HGCmDF+S/sTgNlbXWZZj wkAWT5nc6s9s5wbW X-Received: by 2002:a05:622a:4cc4:b0:4f3:5475:6b10 with SMTP id d75a77b69052e-50ba1bcc884mr6606631cf.8.1774574406996; Thu, 26 Mar 2026 18:20:06 -0700 (PDT) MIME-Version: 1.0 References: <20260326140554.191996-1-hao.ge@linux.dev> <20260326181145.35b559956a45b0efdc9c0450@linux-foundation.org> In-Reply-To: <20260326181145.35b559956a45b0efdc9c0450@linux-foundation.org> From: Suren Baghdasaryan Date: Thu, 26 Mar 2026 18:19:56 -0700 X-Gm-Features: AQROBzBJpvUoyOTB3XCtYnNjPXkRYxHCWOrqxT-ikGoxJhga5jbZYNEfZVJUJeg Message-ID: Subject: Re: [PATCH v2] mm/alloc_tag: clear codetag for pages allocated before page_ext initialization To: Andrew Morton Cc: Hao Ge , Kent Overstreet , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 653A340005 X-Stat-Signature: ix1jmez9mm9eg3zn4wn1hw7kitaupqd5 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1774574408-895101 X-HE-Meta: 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 NZMmI6Y8 zD8wJBSlhUEzbCIpgsltgpGuJMD8NRuob8heGlsEA+DycktLAGlvYIPUTHv90Pv9fqLpr7kpD7y44fsC39FGITlYHNvhgz6/zJGcXhfT/z03fYHY+R8Vka3eTEVN8INHQzh82xhTFEU9dw1aoLua0DhLDCALThfquwI64sK/4XUgBTAyUkRYTqtvZRy0unsb2jSUWNG49XbqRe2D+kttKBIdPRw5BXGo6e/2ULAHDOLWvqufg3BnivC405UvYBrRQqfim1mI7Hp6QALUce3+rp06kLjqU0seLK1KAPMnYaflZiYmzUzS+GJrj/UL1fuJbwwbO0PpD9D+s+6aKaFzuiULIsH3pLoctsdjfbP3shbVgOS8zEqMT0cBOpAvpObNZqVkiLhto7G47jNrT0T+A7G+BXrlKY19aSbzJ65lLza6ng0s= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 26, 2026 at 6:11=E2=80=AFPM Andrew Morton wrote: > > On Thu, 26 Mar 2026 22:05:54 +0800 Hao Ge wrote: > > > Due to initialization ordering, page_ext is allocated and initialized > > relatively late during boot. Some pages have already been allocated > > and freed before page_ext becomes available, leaving their codetag > > uninitialized. > > > > A clear example is in init_section_page_ext(): alloc_page_ext() calls > > kmemleak_alloc(). If the slab cache has no free objects, it falls back > > to the buddy allocator to allocate memory. However, at this point page_= ext > > is not yet fully initialized, so these newly allocated pages have no > > codetag set. These pages may later be reclaimed by KASAN, which causes > > the warning to trigger when they are freed because their codetag ref is > > still empty. > > > > Use a global array to track pages allocated before page_ext is fully > > initialized. The array size is fixed at 8192 entries, and will emit > > a warning if this limit is exceeded. When page_ext initialization > > completes, set their codetag to empty to avoid warnings when they > > are freed later. > > > > Thanks. I'll queue this for review and test. > > But where will I queue it? I don't think it's extra urgent. It is visible only when debugging with CONFIG_MEM_ALLOC_PROFILING_DEBUG. > > > > > Fixes: 93d5440ece3c ("alloc_tag: uninline code gated by mem_alloc_profi= ling_key in page allocator") Hmm. I'm not sure that's the right patch. Technically the problem exists once we introduced CONFIG_MEM_ALLOC_PROFILING_DEBUG. I'll double-check. > > A year ago, so a cc:stable might be needed. > > > +#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG > > otoh, it appears that the bug only hits with > CONFIG_MEM_ALLOC_PROFILING_DEBUG=3Dy? If so, I'll add that (important) > info to the changelog. Correct, it affects only CONFIG_MEM_ALLOC_PROFILING_DEBUG=3Dy and only if !mem_profiling_compressed. > > Do people use CONFIG_MEM_ALLOC_PROFILING_DEBUG much? Is a backport > really needed? IMO backport would be good. > > Either way, it seems that this isn't a very urgent issue so I'm > inclined to add it to the 7.1-rc1 pile, perhaps with a cc:stable. > > Please all share your thoughts with me, thanks. I'm reviewing and testing the patch and there is a race and a couple of smaller issues. I'll post a reply later today.