From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B044633C776 for ; Wed, 17 Sep 2025 14:20:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758118810; cv=none; b=XlEEz2fK971SBAwYamGJerdrVnmnQUXYK8jxpvjFYBbNTP1AwmpHn8kHJAZGFCd97Vsc2g8IEcNrHV3D3iBl7We5mIolenG/DQ1DqBmlm9hbHp+XAmE0Shb0W3MFS6+jCBUmkeJcRbJRjwYDS8/UdpOvvgn1+puD4gGy0T+aa2w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758118810; c=relaxed/simple; bh=1fjNIj619Fl+lLd9OP9BUcAClw93Z2hY3H7Nlzzv4Xc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=e2jcdLLUwkiwjo7oOLoyg+LmbvWUMMavZ+Wo73Fvc9sxdxicA0t6oT4BqWZMdK91at9E+81LjmrrrZAe08vOC3PD08IUQ1WxikiuRVBZsTFClGszR26jZ93LacoT8HZXwMd1xhPA4QyXpvewa46nZfYZdfCtzoiUSw07aUNgtFo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ju8TW1WS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ju8TW1WS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2755DC4CEE7; Wed, 17 Sep 2025 14:20:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758118810; bh=1fjNIj619Fl+lLd9OP9BUcAClw93Z2hY3H7Nlzzv4Xc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ju8TW1WScXt7+y9B+mBjAUjPB6rGDTaKFMxURMULY0VyrjYthHysu2s88SjtAJQpG mzP4tBVg1zaZTFh3yqoccghCFL1QjSbWjaZW1CqldgddDSlBbXb/wMHtWCZpKSSwRc 2X4S0ARuzdLtzIs1qqD7yN6tNmCSlr0WGuJgPHrAvYLhbrowIQMhFv8rTsEgQX/OiR aJfA6WGjh5POC9hS56bLHgvApJENr5TlMIYpqBE6VkavRK1t2V1THv+eYVAFXXZGbr cneR41EUGbtu7cVpMgoh4iQL76Hf0VIQhO4XX1hV1Ol/GApYf7QyTHTD91FKkg4q03 uc22WkIx6j9sw== Date: Wed, 17 Sep 2025 17:20:03 +0300 From: Mike Rapoport To: David Hildenbrand Cc: Alexander Potapenko , akpm@linux-foundation.org, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org, elver@google.com, dvyukov@google.com, kasan-dev@googlegroups.com, Aleksandr Nogikh Subject: Re: [PATCH v1] mm/memblock: Correct totalram_pages accounting with KMSAN Message-ID: References: <20250917123250.3597556-1-glider@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Sep 17, 2025 at 03:29:51PM +0200, David Hildenbrand wrote: > On 17.09.25 14:32, Alexander Potapenko wrote: > > When KMSAN is enabled, `kmsan_memblock_free_pages()` can hold back pages > > for metadata instead of returning them to the early allocator. The callers, > > however, would unconditionally increment `totalram_pages`, assuming the > > pages were always freed. This resulted in an incorrect calculation of the > > total available RAM, causing the kernel to believe it had more memory than > > it actually did. > > > > This patch refactors `memblock_free_pages()` to return the number of pages > > it successfully frees. If KMSAN stashes the pages, the function now > > returns 0; otherwise, it returns the number of pages in the block. > > > > The callers in `memblock.c` have been updated to use this return value, > > ensuring that `totalram_pages` is incremented only by the number of pages > > actually returned to the allocator. This corrects the total RAM accounting > > when KMSAN is active. > > > > Cc: Aleksandr Nogikh > > Fixes: 3c2065098260 ("init: kmsan: call KMSAN initialization routines") > > Signed-off-by: Alexander Potapenko > > --- > > mm/internal.h | 4 ++-- > > mm/memblock.c | 18 +++++++++--------- > > mm/mm_init.c | 9 +++++---- > > 3 files changed, 16 insertions(+), 15 deletions(-) > > > > diff --git a/mm/internal.h b/mm/internal.h > > index 45b725c3dc030..ae1ee6e02eff9 100644 > > --- a/mm/internal.h > > +++ b/mm/internal.h > > @@ -742,8 +742,8 @@ static inline void clear_zone_contiguous(struct zone *zone) > > extern int __isolate_free_page(struct page *page, unsigned int order); > > extern void __putback_isolated_page(struct page *page, unsigned int order, > > int mt); > > -extern void memblock_free_pages(struct page *page, unsigned long pfn, > > - unsigned int order); > > +extern unsigned long memblock_free_pages(struct page *page, unsigned long pfn, > > + unsigned int order); > > extern void __free_pages_core(struct page *page, unsigned int order, > > enum meminit_context context); > > diff --git a/mm/memblock.c b/mm/memblock.c > > index 117d963e677c9..de7ff644d8f4f 100644 > > --- a/mm/memblock.c > > +++ b/mm/memblock.c > > @@ -1834,10 +1834,9 @@ void __init memblock_free_late(phys_addr_t base, phys_addr_t size) > > cursor = PFN_UP(base); > > end = PFN_DOWN(base + size); > > - for (; cursor < end; cursor++) { > > - memblock_free_pages(pfn_to_page(cursor), cursor, 0); > > - totalram_pages_inc(); > > - } > > + for (; cursor < end; cursor++) > > + totalram_pages_add( > > + memblock_free_pages(pfn_to_page(cursor), cursor, 0)); > > } > > That part is clear. But for readability we should probably just do > > if (memblock_free_pages(pfn_to_page(cursor), cursor, 0)) > totalram_pages_inc(); > > Or use a temp variable as an alternative. I prefer this one and totalram_pages_add() after the loop > LGTM > > Reviewed-by: David Hildenbrand > > -- > Cheers > > David / dhildenb > -- Sincerely yours, Mike.