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 82E8A14A81 for ; Thu, 24 Aug 2023 17:20:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC9C2C433C7; Thu, 24 Aug 2023 17:20:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692897641; bh=Js58blEolYg9m5dGNcaI/Yo6w5YBGZH1AFt4gVcApGE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UuoYGzEV0BQMbmQssm6kDbN9OgBc1tPG4zah+lOwcO071COGk5d1NH+B5KX83C/3B gkhcImDjPQ9dDpo9WXuG7IWuXQu3wEr1kngOKLiVpZG15uOZOuyWgqDrBWao/UjRvE zqfHitEVOFcP53ctUTTkuKpOrs7XmUdXX91HmF3k= 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 5.10 111/135] cifs: Release folio lock on fscache read hit. Date: Thu, 24 Aug 2023 19:09:43 +0200 Message-ID: <20230824170622.083460001@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230824170617.074557800@linuxfoundation.org> References: <20230824170617.074557800@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ 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 @@ -4580,9 +4580,9 @@ static int cifs_readpage_worker(struct f io_error: kunmap(page); - unlock_page(page); read_complete: + unlock_page(page); return rc; }