From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailout2.w1.samsung.com (mailout2.w1.samsung.com [210.118.77.12]) (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 034C218800D for ; Tue, 30 Jul 2024 16:08:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.118.77.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722355688; cv=none; b=EHNfbxc+o4qQNKIijf+reK8sAPWq71VxNZFobINGfpF33Db++Ic1mLSTXTgoNFy/mQsDLwLkzuyaiflgzr+dV/WAce/sO9Piq+SutNwtqsCgeNCs4/QVQV0lA/0yQXEQa9bF4XL9XGjG6w7yDkkukT+LQjsvUyOh+VFYMU+dJaA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722355688; c=relaxed/simple; bh=ZDnikaofMadZq4q098kRslXOLdgwFs2m0s1TYIRWPdM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:From:In-Reply-To: Content-Type:References; b=ULdEUrdoSUPeac41Ex4P6XD3lePnLLkxyb7xuK6xjsZQJoi7BTDHtd5UwGlRwRvt3d7o8NCFC1GqJCOvs5btytFbZ4H1UyLb+3C2Jl8fZ99OHj57cPV92NdCgPJdeGrS/KoYTWViV89IvWBe/xLtoch172NnUdafwIFSCIYfBJQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com; spf=pass smtp.mailfrom=samsung.com; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b=EehEXzYf; arc=none smtp.client-ip=210.118.77.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=samsung.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b="EehEXzYf" Received: from eucas1p2.samsung.com (unknown [182.198.249.207]) by mailout2.w1.samsung.com (KnoxPortal) with ESMTP id 20240730160804euoutp02885df9bdde4fc189aa338f03719af189~nCV6RHXru0267202672euoutp020 for ; Tue, 30 Jul 2024 16:08:04 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 mailout2.w1.samsung.com 20240730160804euoutp02885df9bdde4fc189aa338f03719af189~nCV6RHXru0267202672euoutp020 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=samsung.com; s=mail20170921; t=1722355684; bh=D2FnM7fGhh0TbxsAVGiQSzwNJHvbQMWTJOueFpqVWUg=; h=Date:Subject:To:Cc:From:In-Reply-To:References:From; b=EehEXzYfLquHEKjlOSwNSaqxGpjikC047eVlqSNUqWYxBxADsRoy72L4U1514TLRr r+4ZoU8O8vesCmvjvQ4msi3Fc8f4HAICMoFAPj+tkmXhWjKfGJdIFIrzByGv9gQI0f F2Jnl8Z7oVqLXAQbGiNtRX4pNcUtDxmFD+Xmgw/A= Received: from eusmges3new.samsung.com (unknown [203.254.199.245]) by eucas1p1.samsung.com (KnoxPortal) with ESMTP id 20240730160804eucas1p1b48bc9cb1158530295f18182c9592b07~nCV6Dr6t80043700437eucas1p1g; Tue, 30 Jul 2024 16:08:04 +0000 (GMT) Received: from eucas1p2.samsung.com ( [182.198.249.207]) by eusmges3new.samsung.com (EUCPMTA) with SMTP id 48.D2.09620.3EF09A66; Tue, 30 Jul 2024 17:08:03 +0100 (BST) Received: from eusmtrp2.samsung.com (unknown [182.198.249.139]) by eucas1p1.samsung.com (KnoxPortal) with ESMTPA id 20240730160803eucas1p18569f012751560f5d4e5d3c17a88dff4~nCV5rUoug0988309883eucas1p1k; Tue, 30 Jul 2024 16:08:03 +0000 (GMT) Received: from eusmgms2.samsung.com (unknown [182.198.249.180]) by eusmtrp2.samsung.com (KnoxPortal) with ESMTP id 20240730160803eusmtrp27d19536c872a1f8d3baacd67ea532368~nCV5qRUMs2657726577eusmtrp2-; Tue, 30 Jul 2024 16:08:03 +0000 (GMT) X-AuditID: cbfec7f5-d1bff70000002594-7a-66a90fe33c99 Received: from eusmtip1.samsung.com ( [203.254.199.221]) by eusmgms2.samsung.com (EUCPMTA) with SMTP id 89.68.09010.3EF09A66; Tue, 30 Jul 2024 17:08:03 +0100 (BST) Received: from [106.210.134.192] (unknown [106.210.134.192]) by eusmtip1.samsung.com (KnoxPortal) with ESMTPA id 20240730160802eusmtip1cdffbf7ba0218fe3298cf1c448deaa5b~nCV5EDYwC3203132031eusmtip1x; Tue, 30 Jul 2024 16:08:02 +0000 (GMT) Message-ID: Date: Tue, 30 Jul 2024 18:08:02 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/2] mm: let pte_lockptr() consume a pte_t pointer To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Muchun Song , Peter Xu , Oscar Salvador Content-Language: en-US From: Marek Szyprowski In-Reply-To: <82e77547-5116-4ef2-a232-f5ab1fca7e02@redhat.com> Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrAKsWRmVeSWpSXmKPExsWy7djP87qP+VemGazbbWoxZ/0aNouv638x W1zeNYfN4t6a/6wWy3Y+ZLE4M63IYsv+b+wO7B6bPk1i9zgx4zeLx8KGqcwe7/ddZfPYfLra 4/MmuQC2KC6blNSczLLUIn27BK6M+Yt3MRfcEqp4scGkgXEOfxcjJ4eEgInE9aMnmLoYuTiE BFYwSqzf1s8O4XxhlDjZ0s8K4XwGykyYywjT8uD3CWaIxHJGiRl/LkNVfWSU+NK+CCjDwcEr YCfx6VoESAOLgKrE34ZLYM28AoISJ2c+YQGxRQXkJe7fmsEOYgsLeEp8/NfBBNIqIuAmMWFR JMhIZoE1jBJ3++eD1TALiEvcejKfCcRmEzCU6HrbxQZicwKt2rVnPxtEjbxE89bZYMdJCDzh kFj3fT3U1S4Sm/ufMUHYwhKvjm9hh7BlJP7vnM8E0dDOKLHg930oZwKjRMPzW1Dd1hJ3zv1i AzmPWUBTYv0ufYiwo8T0A41gD0sI8EnceCsIcQSfxKRt06HCvBIdbUIQ1WoSs46vg1t78MIl 5gmMSrOQgmUWkjdnIXlnFsLeBYwsqxjFU0uLc9NTi43zUsv1ihNzi0vz0vWS83M3MQIT0el/ x7/uYFzx6qPeIUYmDsZDjBIczEoivPFXlqYJ8aYkVlalFuXHF5XmpBYfYpTmYFES51VNkU8V EkhPLEnNTk0tSC2CyTJxcEo1MBkbNxws2zfhV0xuZdCRuuaMCbddrNQcWfuPSlxYoZlj9er0 45k7q/duDp0toZ3toHn10eOtl3/X/nYxMGr1+bdcMbuBZz/Diuy7ZapCDZVsYk9/NZiVF02a 8KJ8Znufo/L5nT31HxkvB347dWuTzpyoJ8nsJ/S7jV7s0wryCTNNE51sWTttstHfZav3F/st jhI167/edXvbh4riBdcq8jM26HYlMir8iLyqys+0ppPzF/fdPPXTnq2vLdz+rZfibNh0o7/3 rcAU0f85t97eWmRn8ZexwDTHcdOuXRyqyz44yEbusp/4pfvJ6+6nzlOeq293WXy99QxPqMBL b+V9lzd3y149obP1nEdQxPeb0kosxRmJhlrMRcWJALcp3P+zAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrEIsWRmVeSWpSXmKPExsVy+t/xu7qP+VemGcyfIG8xZ/0aNouv638x W1zeNYfN4t6a/6wWy3Y+ZLE4M63IYsv+b+wO7B6bPk1i9zgx4zeLx8KGqcwe7/ddZfPYfLra 4/MmuQC2KD2bovzSklSFjPziElulaEMLIz1DSws9IxNLPUNj81grI1MlfTublNSczLLUIn27 BL2M+Yt3MRfcEqp4scGkgXEOfxcjJ4eEgInEg98nmLsYuTiEBJYySvxpusUCkZCRODmtgRXC Fpb4c62LDaLoPaNE28fjQEUcHLwCdhKfrkWA1LAIqEr8bbjECGLzCghKnJz5BGyOqIC8xP1b M9hBbGEBT4mP/zqYQFpFBNwkJiyKBBnJLLCGUeJ481eoI64xSXw93Q3WwCwgLnHryXwmEJtN wFCi6y3IEZwcnEB7d+3ZzwZRYybRtbWLEcKWl2jeOpt5AqPQLCR3zEIyahaSlllIWhYwsqxi FEktLc5Nzy020itOzC0uzUvXS87P3cQIjLxtx35u2cG48tVHvUOMTByMhxglOJiVRHjjryxN E+JNSaysSi3Kjy8qzUktPsRoCgyMicxSosn5wNjPK4k3NDMwNTQxszQwtTQzVhLn9SzoSBQS SE8sSc1OTS1ILYLpY+LglGpgWi1nOGfZecu0c/unfHu2fM6/z8F1qzQutrr7l05aUqhuES+/ tm2KlspX59snnsXyts+sdNJNZSudfl0iRVDeqltVU7hm/9v3aYuk2R+fzfG+9K9+xY9JwYq9 11ZLyfP1uWaF3pJpk9/0IHBBzJ3+nB+eBsHys/tXtTUvP7Js9yxeWfONRR2an7W8HhgnfRZf lmyhq2U0X+61rlml9bIXORPi+guz37esWdniOok/N/pFcoVoYO6s0My3hl8PRjVt6oiMsQmy 9xO85/SUadb3BM7JVd7vJk9pql/5nDny0PV1OwS2/K+I2b8g4JzugmSlkDCmuo5Fi+foS258 Etc9v4jjH//2m15MCpeUw5OVWIozEg21mIuKEwGKv7TBRQMAAA== X-CMS-MailID: 20240730160803eucas1p18569f012751560f5d4e5d3c17a88dff4 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20240730153058eucas1p2319e4cc985dcdc6e98d08398c33fcfd3 X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20240730153058eucas1p2319e4cc985dcdc6e98d08398c33fcfd3 References: <20240725183955.2268884-1-david@redhat.com> <20240725183955.2268884-2-david@redhat.com> <97d87df8-6076-4df0-90a9-a8f5ddea42e9@samsung.com> <82e77547-5116-4ef2-a232-f5ab1fca7e02@redhat.com> On 30.07.2024 17:49, David Hildenbrand wrote: > On 30.07.24 17:45, David Hildenbrand wrote: >> On 30.07.24 17:30, Marek Szyprowski wrote: >>> On 25.07.2024 20:39, David Hildenbrand wrote: >>>> pte_lockptr() is the only *_lockptr() function that doesn't consume >>>> what would be expected: it consumes a pmd_t pointer instead of a pte_t >>>> pointer. >>>> >>>> Let's change that. The two callers in pgtable-generic.c are easily >>>> adjusted. Adjust khugepaged.c:retract_page_tables() to simply do a >>>> pte_offset_map_nolock() to obtain the lock, even though we won't >>>> actually >>>> be traversing the page table. >>>> >>>> This makes the code more similar to the other variants and avoids >>>> other >>>> hacks to make the new pte_lockptr() version happy. pte_lockptr() users >>>> reside now only in  pgtable-generic.c. >>>> >>>> Maybe, using pte_offset_map_nolock() is the right thing to do because >>>> the PTE table could have been removed in the meantime? At least it >>>> sounds >>>> more future proof if we ever have other means of page table reclaim. >>>> >>>> It's not quite clear if holding the PTE table lock is really required: >>>> what if someone else obtains the lock just after we unlock it? But >>>> we'll >>>> leave that as is for now, maybe there are good reasons. >>>> >>>> This is a preparation for adapting hugetlb page table locking logic to >>>> take the same locks as core-mm page table walkers would. >>>> >>>> Signed-off-by: David Hildenbrand >>> >>> This patch landed in today's linux-next as commit e98970a1d2d4 ("mm: >>> let >>> pte_lockptr() consume a pte_t pointer"). Unfortunately it causes the >>> following issue on most of my ARM 32bit based test boards: >>> >> >> That is ... rather surprising. >> >> The issue below seems to point at __pte_offset_map_lock(), where we >> essentially convert from >> >> ptlock_ptr(page_ptdesc(pmd_page(*pmd))); >> >> to >> >> ptlock_ptr(virt_to_ptdesc(pte)); > > I'm wondering, is highmem involved here such that the PTE would be > kmap'ed and virt_to_page() would not do what we would expect it to do? Yes, highmem is enabled on those boards and all of them have 1GB+ of RAM. For other kernel configuration options see arch/arm/configs/exynos_defconfig. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland