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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6CF03EE49AB for ; Thu, 24 Aug 2023 14:58:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241921AbjHXO5x (ORCPT ); Thu, 24 Aug 2023 10:57:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58932 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241690AbjHXO5o (ORCPT ); Thu, 24 Aug 2023 10:57:44 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EF6F6FD for ; Thu, 24 Aug 2023 07:57:42 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 84CB16701C for ; Thu, 24 Aug 2023 14:57:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 983BCC433C7; Thu, 24 Aug 2023 14:57:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692889062; bh=ZAmFEG4kQZA5Vk/bnuOU5mMuBzzwJ3+pXYTjc/oioSs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dRXJntRje24bhFo6I2Ckn5BKmU8XjMz2bZWbanrLE1B2HtQaKgH9PVdpRmvWMNvY4 7PJ5HJCqYUOzQlcPqya/kF9D73+1z23fUdEUtfn1LczS58334QxUO6kSm7VN5rynGf DSNVmET34F4iHYEIyISombwELylxB1fPXm82EJXU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Russell Harmon , "Paulo Alcantara (SUSE)" , David Howells , Steve French Subject: [PATCH 5.15 111/139] cifs: Release folio lock on fscache read hit. Date: Thu, 24 Aug 2023 16:50:34 +0200 Message-ID: <20230824145028.342695124@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230824145023.559380953@linuxfoundation.org> References: <20230824145023.559380953@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Russell Harmon via samba-technical commit 69513dd669e243928f7450893190915a88f84a2b upstream. Under the current code, when cifs_readpage_worker is called, the call contract is that the callee should unlock the page. This is documented in the read_folio section of Documentation/filesystems/vfs.rst as: > The filesystem should unlock the folio once the read has completed, > whether it was successful or not. Without this change, when fscache is in use and cache hit occurs during a read, the page lock is leaked, producing the following stack on subsequent reads (via mmap) to the page: $ cat /proc/3890/task/12864/stack [<0>] folio_wait_bit_common+0x124/0x350 [<0>] filemap_read_folio+0xad/0xf0 [<0>] filemap_fault+0x8b1/0xab0 [<0>] __do_fault+0x39/0x150 [<0>] do_fault+0x25c/0x3e0 [<0>] __handle_mm_fault+0x6ca/0xc70 [<0>] handle_mm_fault+0xe9/0x350 [<0>] do_user_addr_fault+0x225/0x6c0 [<0>] exc_page_fault+0x84/0x1b0 [<0>] asm_exc_page_fault+0x27/0x30 This requires a reboot to resolve; it is a deadlock. Note however that the call to cifs_readpage_from_fscache does mark the page clean, but does not free the folio lock. This happens in __cifs_readpage_from_fscache on success. Releasing the lock at that point however is not appropriate as cifs_readahead also calls cifs_readpage_from_fscache and *does* unconditionally release the lock after its return. This change therefore effectively makes cifs_readpage_worker work like cifs_readahead. Signed-off-by: Russell Harmon Acked-by: Paulo Alcantara (SUSE) Reviewed-by: David Howells Cc: stable@vger.kernel.org Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/cifs/file.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -4671,9 +4671,9 @@ static int cifs_readpage_worker(struct f io_error: kunmap(page); - unlock_page(page); read_complete: + unlock_page(page); return rc; }