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 012A8394789; Thu, 16 Apr 2026 08:52:12 +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=1776329533; cv=none; b=iZBSjii7DTImaireOlnWjVSpRrfiGYgm0DPHUlL5bjCOPt/sk4P6f6njRNZx08XBGspWtIMN74h615ihBqzjzoLqSXgN1ozzkEDZNYdBSZ2XQIIrw+sry4mLtV5/M+0slhhp4mZBB/fUG0FngwWcqGz+p4xJwNJ8/9zf7wjNmvc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776329533; c=relaxed/simple; bh=g1Hw4WC9BuiiYPxLoJGIqMt62pc+nYnQvs95d3Tl6IE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=PMsyWwG+ztyMfZNYsUdym9quAM3JsE4qIaOdhuIQdHIlA7c+wav0q2SNiHmibzKqC8jxGcJuqRjz9/3foLOoxMSQSPsCupnUGhoarQ4ieuMAuJsXgsCFOaZQROPVD/eBg04h1bxM+CyrzOMaXBDBpzBxcsXMovSWZ+CslzAK4qo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SG1FGUNE; 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="SG1FGUNE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F07BAC2BCAF; Thu, 16 Apr 2026 08:52:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776329532; bh=g1Hw4WC9BuiiYPxLoJGIqMt62pc+nYnQvs95d3Tl6IE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=SG1FGUNEpefy2PFt5pAPpydPb/RP3GVGwvaunJ/FzQfLwUhy55cvvCAZHOPqvXKpc I02KO1WCvxmiAZJBMYl5Cxmqx5wdgVKUN0SUb2yg8cK9h5NYsMKC/yH9NdjBJbzMbN fINLRueFjs6cPypk/vRCriX33RnKA6LsjX2g/pEtnbY6dpBQ62DbthA1HIrKSEob/A tg14TjjV4niiGvv+33alXBnmf9oSoRH+oMn+sG3cWlVLW6Cn25BPAfIaOwM09AWdzk 7cLESpUb2sdyMVI4S0oPe6QVEwB1AlVfnyisb0IEHEsj9j4MB47qI+eBntuo4hiSkR SOkkpg8Zohgmg== Message-ID: <7c5cffc5-f4db-490f-b8aa-6604c32b34f2@kernel.org> Date: Thu, 16 Apr 2026 10:52:05 +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] mm/zone_device: Do not touch device folio after calling ->folio_free() To: Alistair Popple , Matthew Brost Cc: intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Oscar Salvador , Andrew Morton , Balbir Singh , linux-mm@kvack.org, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260410230346.4009855-1-matthew.brost@intel.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/13/26 06:06, Alistair Popple wrote: > On 2026-04-11 at 09:03 +1000, Matthew Brost wrote... >> The contents of a device folio can immediately change after calling >> ->folio_free(), as the folio may be reallocated by a driver with a >> different order. Instead of touching the folio again to extract the >> pgmap, use the local stack variable when calling percpu_ref_put_many(). >> >> Cc: David Hildenbrand >> Cc: Oscar Salvador >> Cc: Andrew Morton >> Cc: Balbir Singh >> Cc: linux-mm@kvack.org >> Cc: linux-cxl@vger.kernel.org >> Cc: linux-kernel@vger.kernel.org >> Fixes: d245f9b4ab80 ("mm/zone_device: support large zone device private folios") >> Signed-off-by: Matthew Brost >> >> --- >> Stack trace: >> >> [ 631.875165] [IGT] xe_exec_system_allocator: starting subtest threads-many-new-prefetch >> [ 632.282992] Oops: general protection fault, probably for non-canonical address 0x900000000000000: 0000 [#1] SMP NOPTI >> [ 632.293469] CPU: 8 UID: 0 PID: 59267 Comm: xe_exec_system_ Not tainted 7.0.0-rc7-xe+ #281 PREEMPT(full) >> [ 632.316023] RIP: 0010:free_zone_device_folio+0x149/0x240 >> [ 632.339782] RSP: 0000:ffffc90023d1fd00 EFLAGS: 00010206 >> [ 632.344947] RAX: 0900000000000000 RBX: 0000000000000001 RCX: 0000000094472d4d >> [ 632.351991] RDX: ffffffff8155c76f RSI: 000000006f2213bf RDI: 000000008e84943a >> [ 632.359042] RBP: ffffea0ff4030001 R08: 0000000000000000 R09: 0000000000000001 >> [ 632.366094] R10: 0000000000000028 R11: 0000000000000000 R12: ffff88811828e400 >> [ 632.373145] R13: 0000000000000000 R14: 000fffffc0000000 R15: 0000000000100073 >> [ 632.380194] FS: 00007f2f0fdfe6c0(0000) GS:ffff88890a7e7000(0000) knlGS:0000000000000000 >> [ 632.388186] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [ 632.393870] CR2: 00007f2f002e90f8 CR3: 0000000106708002 CR4: 0000000000f70ef0 >> [ 632.400919] PKRU: 55555554 >> [ 632.403605] Call Trace: >> [ 632.406039] >> [ 632.408131] do_swap_page+0x146d/0x18c0 >> [ 632.411938] ? __pte_offset_map+0x3e/0x190 >> [ 632.415994] __handle_mm_fault+0x6e8/0x8d0 >> [ 632.420053] handle_mm_fault+0xbf/0x250 >> [ 632.423855] ? lock_mm_and_find_vma+0x41/0x6f0 >> [ 632.428256] do_user_addr_fault+0x168/0x690 >> [ 632.432399] exc_page_fault+0x74/0x200 >> [ 632.436117] asm_exc_page_fault+0x26/0x30 >> [ 632.440092] RIP: 0033:0x5587554ff70d >> [ 632.462142] RSP: 002b:00007f2f0fdfc970 EFLAGS: 00010246 >> [ 632.467308] RAX: 0000000000003fc0 RBX: 00007f2f082e1fc0 RCX: 00007f2f12b3287d >> [ 632.474355] RDX: 0000000000000000 RSI: 00000000c048644a RDI: 0000000000000003 >> [ 632.481404] RBP: 00007f2f082e1fc0 R08: 00007f2f0fdfc958 R09: 0000000000000066 >> [ 632.488450] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 >> [ 632.495495] R13: 00007f2f082de000 R14: 0000000000c00002 R15: 00007f2f1319e000 >> [ 632.502547] > > I'm not sure, but I think Andrew likes the stack traces included in the actual > commit messages. I've certainly found it helpful when debugging traces reported > from the field so would prefer it there. Agreed. > >> --- >> mm/memremap.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/memremap.c b/mm/memremap.c >> index ac7be07e3361..053842d45cb1 100644 >> --- a/mm/memremap.c >> +++ b/mm/memremap.c >> @@ -454,7 +454,7 @@ void free_zone_device_folio(struct folio *folio) >> if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->folio_free)) >> break; >> pgmap->ops->folio_free(folio); >> - percpu_ref_put_many(&folio->pgmap->ref, nr); >> + percpu_ref_put_many(&pgmap->ref, nr); > I assume the ref keeps pgmap alive, such that that cannot go away after the folio_free(). Acked-by: David Hildenbrand (Arm) -- Cheers, David