From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 433EEC44508 for ; Wed, 15 Jul 2026 13:37:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 38C6B6B00CD; Wed, 15 Jul 2026 09:37:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 33C776B00D2; Wed, 15 Jul 2026 09:37:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1DE846B00D4; Wed, 15 Jul 2026 09:37:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id DAF8F6B00CD for ; Wed, 15 Jul 2026 09:37:54 -0400 (EDT) Received: from smtpin01.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 1D87F1A0193 for ; Wed, 15 Jul 2026 13:01:28 +0000 (UTC) X-FDA: 84991022256.01.7F58F93 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf21.hostedemail.com (Postfix) with ESMTP id 5750E1C0005 for ; Wed, 15 Jul 2026 13:01:26 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=gWf54nLm; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf21.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784120486; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=wUXuEqTpyi55WJTpZHqeaTPsyp4qkuq1mFSEddNo1tA=; b=0vQTqxc1d9A43gNVWT/BPA4dN4Op0H9CLqBNUUyRySdHe/GXhwYKs9Su1SMkzIfvg7OcfI Gjy5DfzGMjaT9QSqRgJmJDiijbbzph1lqYk3zIwl3Iv2HbgW8s3J1Xx8IiPG0ebp49tWTj AOw0q1f6llk8h1W0Wi40R3L7enS9oiY= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=gWf54nLm; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf21.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784120486; b=UHvNrHvOJWFIKlYnb2TJXpvdZC2qxjJOKarSRL3hakHhsoMcjoItUnqT1QKOXRsx1fUgHZ IfVDJ5GXnMrZE1C/zDdfXnBbaRgIipfxAYD9UbVUiNjQtpnLK80bWVPVPIIE9l1B5G1uxo Bkx2fxDmrPx2+/zEQfZ0sKk5EN+dBa0= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id AA91D6001A; Wed, 15 Jul 2026 13:01:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 397A31F000E9; Wed, 15 Jul 2026 13:01:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784120485; bh=wUXuEqTpyi55WJTpZHqeaTPsyp4qkuq1mFSEddNo1tA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=gWf54nLmEwWJANF5qUC6poTKMViOSzEpoFuUKkjJj63i8H9uciYM6Dlgpy27x1WZp 4Nw2fRu/qXdKsuvJ6taqOeOQeKbrO9UqxRGcK2DhOjKN3flD4HKVB57Uvj+f14KnVr VPzyVR7iuSIdM4xo2zbz5c40benVATHoca0c+Ls+3c6h6GT44ZSGFrL+6C2UCl6SGd +frsS5rS/CWL4+tNaQu90B+aRXEviBOQwiFgrkYAXSOk8K/bdY9HtIMk2gJW2Cy2MX f31aWYHXfliY5eoDu6elZcL524x422cFRrEthYOJ3xufmQIEmkM8m/Acc+JADTzuvg 0r2w6G5b9EWQw== Message-ID: Date: Wed, 15 Jul 2026 15:01:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/5] mm/memory-failure: keep the folio, not the poisoned subpage, locked across split To: Kiryl Shutsemau , Zi Yan Cc: Andrew Morton , Lorenzo Stoakes , Miaohe Lin , Naoya Horiguchi , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Hao Zhang , Hao Zhang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260714122344.351895-1-kirill@shutemov.name> <20260714122344.351895-2-kirill@shutemov.name> <18fe5529-2ad5-4330-a362-708a152bacee@kernel.org> <66A57599-EDA0-4E99-B073-F2AE0B2ED708@nvidia.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 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5750E1C0005 X-Stat-Signature: 98584zktpx3mxrqoo5ok31etdi11dy7s X-Rspam-User: X-HE-Tag: 1784120486-615596 X-HE-Meta: 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 X/aKEpQK IIfyh4wX8eiEli6RXy65FlUVnJh/JM5qT59S+L2ty2Cq4NGQthJ3PNz3bq6ucB9qnMuOWAZeyVcjBlIwoS6k6LPajDoP+7keQLJ4HlW9xiE/gz9TAlgPxhvLNXuIYG2LEhDsh25yfijOuOMFWilxbPXf7PuF3RqX/dM5joJtmhbTgF0TPouhL352A3foHp5jD3rJFk+jdFRO1ZLQiIOkidmO+8+MXWDdH81IJNH0DpEKLTh5XCS9kj9J/adlIhhKofyJEmDSWtWYruWHLAeYEiCdZXxv7RXcSdJs1vwTIlIU3zTAd2USLOEtukEZGDGnlm/OfNsn8b8fHXIOl5jyt0/unR/QsMl+Eu48zHYwb7FNy4fM= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/15/26 12:42, Kiryl Shutsemau wrote: > On Tue, Jul 14, 2026 at 01:31:54PM -0400, Zi Yan wrote: >> On Tue Jul 14, 2026 at 12:40 PM EDT, Kiryl Shutsemau wrote: >>> >>> I saw this option too, but I wound rather not go this path. >>> >>> iput() still can lead to inode eviction an bunch of random filesystem >>> complexity under us. I don't think we want to think about other >>> fs-related locking issues in split context. >> >> Your reasoning makes sense to me. Let's ignore this option. >> >> For your patch 2, we might want something like below to avoid over >> rejecting splits. WDYT? >> >> offset = folio_page_idx(folio, lock_at); >> >> if (split_type == SPLIT_TYPE_UNIFORM) >> lock_at_index = folio->index + round_down(offset, 1UL << new_order); >> else >> /* @lock_at in non uniform split is always @folio */ >> lock_at_index = folio->index; >> >> if (lock_at_index >= end) { >> ret = -EBUSY; >> goto out_unlock; >> } >> > > Right. With the -EBUSY condition growing this hairy -- and having to stay > correct for non-uniform splits too -- just moving i_mmap_unlock_read() out > of the window looks more attractive. > > This is really Hao's original patch with the reasoning corrected, so I kept > him as author. v3 below. > > ---------------------------------------------------------------------- > > From: "Kiryl Shutsemau (Meta)" > Subject: [PATCH v3] mm/huge_memory: unlock i_mmap_rwsem before releasing > after-split folios > > __folio_split() keeps dereferencing the mapping after the split: > shmem_uncharge(mapping->host) and remap_page() while the folios are still > frozen/locked, and i_mmap_unlock_read(mapping) at the very end, after the > after-split folios have been unlocked and freed. > > Nothing holds an inode reference across that. The split relies on @folio > -- which the beyond-EOF drop loop never removes, as it starts at > folio_next(folio) -- staying locked and in the page cache to hold off > eviction. But the unlock loop unlocks @folio before i_mmap_unlock_read() > runs. If the caller's @lock_at is a tail beyond EOF, as memory_failure() > passes when splitting a poisoned tail of a shmem THP that reaches past > i_size during truncation, it too is gone from the page cache; so once > @folio is unlocked no locked, in-cache folio pins the inode, and a > concurrent final iput() can evict and RCU-free it before > i_mmap_unlock_read() touches i_mmap_rwsem: > > BUG: KASAN: slab-use-after-free in __up_read+0x634/0x790 > i_mmap_unlock_read include/linux/fs.h:537 [inline] > __folio_split+0x732/0x1640 mm/huge_memory.c:4100 > try_to_split_thp_page+0xab/0x390 mm/memory-failure.c:1675 > memory_failure+0x1394/0x26e0 mm/memory-failure.c:2470 > > Freed by task 4601: > shmem_free_in_core_inode+0x54/0xb0 mm/shmem.c:5177 > evict+0x57f/0xac0 fs/inode.c:870 > > Do every mapping dereference while @folio still pins the inode: drop > i_mmap_rwsem right after remap_page(), before the loop that unlocks and > frees the after-split folios, and clear @mapping so the exit path does not > unlock it again. shmem_uncharge() and remap_page() already run before that > point, so after this nothing past the unlock loop touches the inode or the > mapping. > > This is now a rule the split depends on, alongside keeping @folio frozen > until the page cache is updated: no inode or mapping dereference once the > after-split folios start being unlocked. > > Reported-by: Hao Zhang > Closes: https://lore.kernel.org/linux-mm/20260710071344.GA106129@zh-pc > Fixes: baa355fd3314 ("thp: file pages support for split_huge_page()") > Cc: > Co-developed-by: Hao Zhang > Signed-off-by: Hao Zhang > Signed-off-by: Kiryl Shutsemau (Meta) > --- > mm/huge_memory.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 2bccb0a53a0a..abaea34ef558 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -4109,6 +4109,18 @@ static int __folio_split(struct folio *folio, unsigned int new_order, > > remap_page(folio, 1 << old_order, ttu_flags); > > + /* > + * Drop the mapping while the inode is still pinned. @folio stays > + * locked and present in the page cache until the loop below, so > + * eviction cannot free the inode yet; @lock_at is not enough, it may > + * be a tail beyond EOF that the split already dropped from the page > + * cache. Nothing past this point may touch the inode or the mapping. > + */ > + if (mapping) { > + i_mmap_unlock_read(mapping); > + mapping = NULL; > + } > + > /* > * Unlock all after-split folios except the one containing > * @lock_at page. If @folio is not split, it will be kept locked. LGTM Acked-by: David Hildenbrand (Arm) -- Cheers, David