From nobody Fri Dec 19 20:34:16 2025 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AC50BEAF1; Wed, 4 Jun 2025 04:15:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749010546; cv=none; b=lT1lMsts1LzNVm8J5yvCDA92jv4yJ4WN4tj++Foczskx8gF06wZ34dA7lw7x9DEjijT5P9aTHmbmPHL8iQuF29GAQuOqGyPoTYckagC6RBAW1wuqkBqnek/nNPqHWMf/lITm6Nms8fkj7o/tNbZGWUMGKRV6dgfpnKvbqGr9mEE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749010546; c=relaxed/simple; bh=TISq2IOqcxgXqiUwD6UtnHmSV44dC7o5qVYxd3d8+2Q=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=krl9kK9/WiLDIVBHiX1bxZbriJ5nwKRkrQk5BI1z8LAussZ/Pw80iVbPfdRlMib4TcZ6tY/qPIauTNHL+ob/EIbttzVXmfMjwr3R4LsXdAM6oRdrXB8iF19xvBHFa8XiJ7WXDtg28gwge4D9WysgFk9V8CzO+gwlZpOHWMHjFbM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AFB641756; Tue, 3 Jun 2025 21:15:25 -0700 (PDT) Received: from MacBook-Pro.blr.arm.com (MacBook-Pro.blr.arm.com [10.164.18.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 731363F673; Tue, 3 Jun 2025 21:15:39 -0700 (PDT) From: Dev Jain To: akpm@linux-foundation.org, willy@infradead.org Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@redhat.com, anshuman.khandual@arm.com, ryan.roberts@arm.com, ziy@nvidia.com, aneesh.kumar@kernel.org, Dev Jain Subject: [PATCH v2] xarray: Add a BUG_ON() to ensure caller is not sibling Date: Wed, 4 Jun 2025 09:45:33 +0530 Message-Id: <20250604041533.91198-1-dev.jain@arm.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Suppose xas is pointing somewhere near the end of the multi-entry batch. Then it may happen that the computed slot already falls beyond the batch, thus breaking the loop due to !xa_is_sibling(), and computing the wrong order. For example, suppose we have a shift-6 node having an order-9 entry =3D> 8 - 1 =3D 7 siblings, so assume the slots are at offset 0 till 7= in this node. If xas->xa_offset is 6, then the code will compute order as 1 + xas->xa_node->shift =3D 7. Therefore, the order computation must start from the beginning of the multi-slot entries, that is, the non-sibling entry. Thus ensure that the caller is aware of this by triggering a BUG when the entry is a sibling entry. Note that this BUG_ON() is only active while running selftests, so there is no overhead in a running kernel. Signed-off-by: Dev Jain Acked-by: Zi Yan --- v1->v2: - Expand changelog, add comment Based on Torvalds' master branch. lib/xarray.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/lib/xarray.c b/lib/xarray.c index 76dde3a1cacf..ae3d80f4b4ee 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1910,6 +1910,7 @@ EXPORT_SYMBOL(xa_store_range); * @xas: XArray operation state. * * Called after xas_load, the xas should not be in an error state. + * The xas should not be pointing to a sibling entry. * * Return: A number between 0 and 63 indicating the order of the entry. */ @@ -1920,6 +1921,8 @@ int xas_get_order(struct xa_state *xas) if (!xas->xa_node) return 0; =20 + XA_NODE_BUG_ON(xas->xa_node, xa_is_sibling(xa_entry(xas->xa, + xas->xa_node, xas->xa_offset))); for (;;) { unsigned int slot =3D xas->xa_offset + (1 << order); =20 --=20 2.30.2