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 36EE949620; Mon, 17 Mar 2025 00:41:11 +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=1742172072; cv=none; b=IWAKLN9lltO3XtYuga63ZP7InmuCO+fbkyFcWGUV9AAtznhwWDiiWKwOctNHSQZHqPsaxzQgwwcsvPGBtsC1M5WtpfmcJvfHQ/wl7l++bO8VqRu0BiB3wlIBvJ1xhaK+VdBQY4iBv0GMUq6hjZ7LuX030kpLN/hUoUFwsRk3NHI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742172072; c=relaxed/simple; bh=qyN9wuDrjIMxWs3klzzZDrkcTasmeQThEFCHfHFe8gE=; h=Date:To:From:Subject:Message-Id; b=gh9e91d9S9owrmI2wZjddJJ4tC4tFmLMLKW/MrFFwV7sDU/3Ws8cc+6/UshTyqh1gx7CRUnMSpQl+gNg5CfciQzDJA9uFY0F4YqHuiPc/Fj+DZ9dQOyMmOVx+W1dmAN3r/osODQbnobsOEIe/Oo4pqOEQyQFqNKi+NS0YpoHxSs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=a84x+8yM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="a84x+8yM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9CE92C4CEDD; Mon, 17 Mar 2025 00:41:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1742172071; bh=qyN9wuDrjIMxWs3klzzZDrkcTasmeQThEFCHfHFe8gE=; h=Date:To:From:Subject:From; b=a84x+8yMX4wAknkPbYbHjkPFFIVg1uzSCEPygS/fYMsBAKr0TYaU8Z1mIO9BJ3b7T hmTzugLRMSArC9tqwTo0cP5zomo3cQw3cVZb8hHbx7KMYl6U9vv5iiAwI3JNx2ld5G XF6PIFKzxPaa515K6+RCb+aCtctbC8DI5yQ9yPBI= Date: Sun, 16 Mar 2025 17:41:11 -0700 To: mm-commits@vger.kernel.org,willy@infradead.org,wangkefeng.wang@huawei.com,stable@vger.kernel.org,ryan.roberts@arm.com,quic_charante@quicinc.com,liushixin2@huawei.com,ioworker0@gmail.com,hughd@google.com,david@redhat.com,baolin.wang@linux.alibaba.com,baohua@kernel.org,ziy@nvidia.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] mm-migrate-fix-shmem-xarray-update-during-migration.patch removed from -mm tree Message-Id: <20250317004111.9CE92C4CEDD@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/migrate: fix shmem xarray update during migration has been removed from the -mm tree. Its filename was mm-migrate-fix-shmem-xarray-update-during-migration.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Zi Yan Subject: mm/migrate: fix shmem xarray update during migration Date: Wed, 5 Mar 2025 15:04:03 -0500 A shmem folio can be either in page cache or in swap cache, but not at the same time. Namely, once it is in swap cache, folio->mapping should be NULL, and the folio is no longer in a shmem mapping. In __folio_migrate_mapping(), to determine the number of xarray entries to update, folio_test_swapbacked() is used, but that conflates shmem in page cache case and shmem in swap cache case. It leads to xarray multi-index entry corruption, since it turns a sibling entry to a normal entry during xas_store() (see [1] for a userspace reproduction). Fix it by only using folio_test_swapcache() to determine whether xarray is storing swap cache entries or not to choose the right number of xarray entries to update. [1] https://lore.kernel.org/linux-mm/Z8idPCkaJW1IChjT@casper.infradead.org/ Note: In __split_huge_page(), folio_test_anon() && folio_test_swapcache() is used to get swap_cache address space, but that ignores the shmem folio in swap cache case. It could lead to NULL pointer dereferencing when a in-swap-cache shmem folio is split at __xa_store(), since !folio_test_anon() is true and folio->mapping is NULL. But fortunately, its caller split_huge_page_to_list_to_order() bails out early with EBUSY when folio->mapping is NULL. So no need to take care of it here. Link: https://lkml.kernel.org/r/20250305200403.2822855-1-ziy@nvidia.com Fixes: fc346d0a70a1 ("mm: migrate high-order folios in swap cache correctly") Signed-off-by: Zi Yan Reported-by: Liu Shixin Closes: https://lore.kernel.org/all/28546fb4-5210-bf75-16d6-43e1f8646080@huawei.com/ Suggested-by: Hugh Dickins Reviewed-by: Matthew Wilcox (Oracle) Reviewed-by: Baolin Wang Cc: Barry Song Cc: Charan Teja Kalla Cc: David Hildenbrand Cc: Hugh Dickins Cc: Kefeng Wang Cc: Lance Yang Cc: Ryan Roberts Cc: Signed-off-by: Andrew Morton --- mm/migrate.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) --- a/mm/migrate.c~mm-migrate-fix-shmem-xarray-update-during-migration +++ a/mm/migrate.c @@ -518,15 +518,13 @@ static int __folio_migrate_mapping(struc if (folio_test_anon(folio) && folio_test_large(folio)) mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1); folio_ref_add(newfolio, nr); /* add cache reference */ - if (folio_test_swapbacked(folio)) { + if (folio_test_swapbacked(folio)) __folio_set_swapbacked(newfolio); - if (folio_test_swapcache(folio)) { - folio_set_swapcache(newfolio); - newfolio->private = folio_get_private(folio); - } + if (folio_test_swapcache(folio)) { + folio_set_swapcache(newfolio); + newfolio->private = folio_get_private(folio); entries = nr; } else { - VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio); entries = 1; } _ Patches currently in -mm which might be from ziy@nvidia.com are selftests-mm-make-file-backed-thp-split-work-by-writing-pmd-size-data.patch mm-huge_memory-allow-split-shmem-large-folio-to-any-lower-order.patch selftests-mm-test-splitting-file-backed-thp-to-any-lower-order.patch xarray-add-xas_try_split-to-split-a-multi-index-entry.patch mm-huge_memory-add-two-new-not-yet-used-functions-for-folio_split.patch mm-huge_memory-add-two-new-not-yet-used-functions-for-folio_split-fix.patch mm-huge_memory-add-two-new-not-yet-used-functions-for-folio_split-fix-2.patch mm-huge_memory-move-folio-split-common-code-to-__folio_split.patch mm-huge_memory-add-buddy-allocator-like-non-uniform-folio_split.patch mm-huge_memory-remove-the-old-unused-__split_huge_page.patch mm-huge_memory-add-folio_split-to-debugfs-testing-interface.patch mm-truncate-use-folio_split-in-truncate-operation.patch selftests-mm-add-tests-for-folio_split-buddy-allocator-like-split.patch mm-filemap-use-xas_try_split-in-__filemap_add_folio.patch mm-shmem-use-xas_try_split-in-shmem_split_large_entry.patch