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[2620:137:e000::1:20]) by mx.google.com with ESMTP id z72-20020a509e4e000000b004596db363c4si10975935ede.264.2022.10.17.19.50.25; Mon, 17 Oct 2022 19:50:49 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230077AbiJRCcv (ORCPT + 99 others); Mon, 17 Oct 2022 22:32:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229822AbiJRCcs (ORCPT ); Mon, 17 Oct 2022 22:32:48 -0400 Received: from smtp01.aussiebb.com.au (smtp01.aussiebb.com.au [121.200.0.92]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7630C92F48; Mon, 17 Oct 2022 19:32:47 -0700 (PDT) Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp01.aussiebb.com.au (Postfix) with ESMTP id B9A01100626; Tue, 18 Oct 2022 13:32:44 +1100 (AEDT) X-Virus-Scanned: Debian amavisd-new at smtp01.aussiebb.com.au Received: from smtp01.aussiebb.com.au ([127.0.0.1]) by localhost (smtp01.aussiebb.com.au [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 6T_nZIWt-tY1; Tue, 18 Oct 2022 13:32:44 +1100 (AEDT) Received: by smtp01.aussiebb.com.au (Postfix, from userid 116) id A5E6810061D; Tue, 18 Oct 2022 13:32:44 +1100 (AEDT) X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 Received: from donald.themaw.net (180-150-90-198.b4965a.per.nbn.aussiebb.net [180.150.90.198]) by smtp01.aussiebb.com.au (Postfix) with ESMTP id E5B0B1005F4; Tue, 18 Oct 2022 13:32:42 +1100 (AEDT) Subject: [PATCH 1/2] kernfs: dont take i_lock on inode attr read From: Ian Kent To: Greg Kroah-Hartman , Tejun Heo Cc: Minchan Kim , Eric Sandeen , Al Viro , Rick Lindsley , David Howells , Miklos Szeredi , Carlos Maiolino , linux-fsdevel , Kernel Mailing List Date: Tue, 18 Oct 2022 10:32:42 +0800 Message-ID: <166606036215.13363.1288735296954908554.stgit@donald.themaw.net> In-Reply-To: <166606025456.13363.3829702374064563472.stgit@donald.themaw.net> References: <166606025456.13363.3829702374064563472.stgit@donald.themaw.net> User-Agent: StGit/1.4 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1746992051125035778?= X-GMAIL-MSGID: =?utf-8?q?1746992051125035778?= The kernfs write lock is held when the kernfs node inode attributes are updated. Therefore, when either kernfs_iop_getattr() or kernfs_iop_permission() are called the kernfs node inode attributes won't change. Consequently concurrent kernfs_refresh_inode() calls always copy the same values from the kernfs node. So there's no need to take the inode i_lock to get consistent values for generic_fillattr() and generic_permission(), the kernfs read lock is sufficient. Signed-off-by: Ian Kent Reviewed-by: Miklos Szeredi Acked-by: Tejun Heo Signed-off-by: Ian Kent Acked-by: Miklos Szeredi Reviewed-by: Imran Khan --- fs/kernfs/inode.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index 3d783d80f5da..74f3453f4639 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -190,10 +190,8 @@ int kernfs_iop_getattr(struct user_namespace *mnt_userns, struct kernfs_root *root = kernfs_root(kn); down_read(&root->kernfs_rwsem); - spin_lock(&inode->i_lock); kernfs_refresh_inode(kn, inode); generic_fillattr(&init_user_ns, inode, stat); - spin_unlock(&inode->i_lock); up_read(&root->kernfs_rwsem); return 0; @@ -288,10 +286,8 @@ int kernfs_iop_permission(struct user_namespace *mnt_userns, root = kernfs_root(kn); down_read(&root->kernfs_rwsem); - spin_lock(&inode->i_lock); kernfs_refresh_inode(kn, inode); ret = generic_permission(&init_user_ns, inode, mask); - spin_unlock(&inode->i_lock); up_read(&root->kernfs_rwsem); return ret;