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 9EF413AF654 for ; Mon, 30 Mar 2026 09:24:39 +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=1774862679; cv=none; b=ld1j5uxnK6srMUNyMoWVHvi16efaxCagfSxQ7sl95zKoO4ndA6a48dTqTfyn7rdWZJKpSvijHRjMBqvfbWj+8J8epUXKfNrzqXRA0bcX1lGBBsfJui78KW/X0QiwER7gHBlzHRF/qpwO84Q/3yP6m7dVT9X6IGYWlvAYGKyOQSg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774862679; c=relaxed/simple; bh=18SEuQZoe3zrE+6ZU7WvNiYRPkaMVo2T9sB2y12rRnk=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=mAgUc9PIH8h+jAj5Sv8Wn3vDgJtAjgs73c/t9oVcnLfTrT21PWV7bh2CDBhd5Y2kdypQ7fPtpAUkB5XIzltQCW3JftD/MFuK0yju2+ZOThEEKWKH/ixGpOk7y3MEs9aNxilWdUeP/gKCJe56opgQgYHksk7N2bD5pJM6icdmji8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=K43lH2PA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="K43lH2PA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B737FC4CEF7; Mon, 30 Mar 2026 09:24:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774862679; bh=18SEuQZoe3zrE+6ZU7WvNiYRPkaMVo2T9sB2y12rRnk=; h=Subject:To:Cc:From:Date:From; b=K43lH2PA6tJ/SwgK+2T0YWZOKKgK7L/+IEyBt1Jka+/B8sX6l9LyejLjF4Nwl3xjk QevA/oLrtUxjousLFydaYYNead/CagJPL6VA4WZPRZFNFqOaYbDZbyh/sHJwdYiLaV Eniy8H+/8ITxYAuq5eydyxZgb3FFEbO1/nKvVBMM= Subject: FAILED: patch "[PATCH] mm/huge_memory: fix folio isn't locked in softleaf_to_folio()" failed to apply to 6.18-stable tree To: tujinjiang@huawei.com,akpm@linux-foundation.org,baohua@kernel.org,david@kernel.org,liam.howlett@oracle.com,ljs@kernel.org,mhocko@suse.com,rppt@kernel.org,ryan.roberts@arm.com,stable@vger.kernel.org,sunnanyong@huawei.com,surenb@google.com,vbabka@kernel.org,wangkefeng.wang@huawei.com Cc: From: Date: Mon, 30 Mar 2026 11:24:35 +0200 Message-ID: <2026033035-wrongdoer-latticed-bc35@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 4c5e7f0fcd592801c9cc18f29f80fbee84eb8669 # git commit -s git send-email --to '' --in-reply-to '2026033035-wrongdoer-latticed-bc35@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 4c5e7f0fcd592801c9cc18f29f80fbee84eb8669 Mon Sep 17 00:00:00 2001 From: Jinjiang Tu Date: Thu, 19 Mar 2026 09:25:41 +0800 Subject: [PATCH] mm/huge_memory: fix folio isn't locked in softleaf_to_folio() On arm64 server, we found folio that get from migration entry isn't locked in softleaf_to_folio(). This issue triggers when mTHP splitting and zap_nonpresent_ptes() races, and the root cause is lack of memory barrier in softleaf_to_folio(). The race is as follows: CPU0 CPU1 deferred_split_scan() zap_nonpresent_ptes() lock folio split_folio() unmap_folio() change ptes to migration entries __split_folio_to_order() softleaf_to_folio() set flags(including PG_locked) for tail pages folio = pfn_folio(softleaf_to_pfn(entry)) smp_wmb() VM_WARN_ON_ONCE(!folio_test_locked(folio)) prep_compound_page() for tail pages In __split_folio_to_order(), smp_wmb() guarantees page flags of tail pages are visible before the tail page becomes non-compound. smp_wmb() should be paired with smp_rmb() in softleaf_to_folio(), which is missed. As a result, if zap_nonpresent_ptes() accesses migration entry that stores tail pfn, softleaf_to_folio() may see the updated compound_head of tail page before page->flags. This issue will trigger VM_WARN_ON_ONCE() in pfn_swap_entry_folio() because of the race between folio split and zap_nonpresent_ptes() leading to a folio incorrectly undergoing modification without a folio lock being held. This is a BUG_ON() before commit 93976a20345b ("mm: eliminate further swapops predicates"), which in merged in v6.19-rc1. To fix it, add missing smp_rmb() if the softleaf entry is migration entry in softleaf_to_folio() and softleaf_to_page(). [tujinjiang@huawei.com: update function name and comments] Link: https://lkml.kernel.org/r/20260321075214.3305564-1-tujinjiang@huawei.com Link: https://lkml.kernel.org/r/20260319012541.4158561-1-tujinjiang@huawei.com Fixes: e9b61f19858a ("thp: reintroduce split_huge_page()") Signed-off-by: Jinjiang Tu Acked-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (Oracle) Cc: Barry Song Cc: Kefeng Wang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Nanyong Sun Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton diff --git a/include/linux/leafops.h b/include/linux/leafops.h index a9ff94b744f2..05673d3529e7 100644 --- a/include/linux/leafops.h +++ b/include/linux/leafops.h @@ -363,6 +363,23 @@ static inline unsigned long softleaf_to_pfn(softleaf_t entry) return swp_offset(entry) & SWP_PFN_MASK; } +static inline void softleaf_migration_sync(softleaf_t entry, + struct folio *folio) +{ + /* + * Ensure we do not race with split, which might alter tail pages into new + * folios and thus result in observing an unlocked folio. + * This matches the write barrier in __split_folio_to_order(). + */ + smp_rmb(); + + /* + * Any use of migration entries may only occur while the + * corresponding page is locked + */ + VM_WARN_ON_ONCE(!folio_test_locked(folio)); +} + /** * softleaf_to_page() - Obtains struct page for PFN encoded within leaf entry. * @entry: Leaf entry, softleaf_has_pfn(@entry) must return true. @@ -374,11 +391,8 @@ static inline struct page *softleaf_to_page(softleaf_t entry) struct page *page = pfn_to_page(softleaf_to_pfn(entry)); VM_WARN_ON_ONCE(!softleaf_has_pfn(entry)); - /* - * Any use of migration entries may only occur while the - * corresponding page is locked - */ - VM_WARN_ON_ONCE(softleaf_is_migration(entry) && !PageLocked(page)); + if (softleaf_is_migration(entry)) + softleaf_migration_sync(entry, page_folio(page)); return page; } @@ -394,12 +408,8 @@ static inline struct folio *softleaf_to_folio(softleaf_t entry) struct folio *folio = pfn_folio(softleaf_to_pfn(entry)); VM_WARN_ON_ONCE(!softleaf_has_pfn(entry)); - /* - * Any use of migration entries may only occur while the - * corresponding folio is locked. - */ - VM_WARN_ON_ONCE(softleaf_is_migration(entry) && - !folio_test_locked(folio)); + if (softleaf_is_migration(entry)) + softleaf_migration_sync(entry, folio); return folio; }