From patchwork Thu Sep 17 12:39:45 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 7206371 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 5EFCD9F336 for ; Thu, 17 Sep 2015 12:40:03 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 6E5F52080E for ; Thu, 17 Sep 2015 12:40:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91F9720824 for ; Thu, 17 Sep 2015 12:40:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751937AbbIQMj6 (ORCPT ); Thu, 17 Sep 2015 08:39:58 -0400 Received: from mail-yk0-f181.google.com ([209.85.160.181]:33473 "EHLO mail-yk0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751887AbbIQMj4 (ORCPT ); Thu, 17 Sep 2015 08:39:56 -0400 Received: by ykft14 with SMTP id t14so15186234ykf.0 for ; Thu, 17 Sep 2015 05:39:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=EQ16Hh+rD/nw3ptqNtzrkERuqK+qkbe/Wjco/IKw5f4=; b=MqLi/oMQ/gjWaQRt7a0IzF8due1DgTcGsN9aQ/57SJf3HjGEiLZCQ75jAhe0F9ORsY xCR6YjiBYCqHJeVkkf6uSEKGJN53YnbtaXLW4962QWEEM8B69EDonXT5htM4dxLT1lk2 4buuanMax6iwpfisutogyLUMRurCAHbxJbIPWV00WJ5e58FZFWRwhUhF4NtPCPdp5wE/ 0vQN/mgUo3MbRYB0lXW1JnUIwefXv5ojimGoDL/vzmFboho+4PnCFDcf0bhuRV5jZX6p 0aT+xZvyOpSTywVtecY4/dr9TlKBC0vv1kGX8TD1d8z2bZzoKzaUd1/UXD9MvJf5LY6A WY6w== X-Gm-Message-State: ALoCoQkwIDLxg+RXShwlR60wJMdmfA3AAqb9rrGfI28/i9OYcmRT7VtAelCjGr1RLJAeMBIlvKjI X-Received: by 10.170.63.85 with SMTP id f82mr33781074ykf.105.1442493595475; Thu, 17 Sep 2015 05:39:55 -0700 (PDT) Received: from tlielax.poochiereds.net ([2606:a000:1105:8e:3a60:77ff:fe93:a95d]) by smtp.googlemail.com with ESMTPSA id q128sm1878652ywf.27.2015.09.17.05.39.54 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 17 Sep 2015 05:39:54 -0700 (PDT) From: Jeff Layton X-Google-Original-From: Jeff Layton To: Al Viro Cc: bfields@fieldses.org, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/4] fs: add a kerneldoc header to fput Date: Thu, 17 Sep 2015 08:39:45 -0400 Message-Id: <1442493587-32499-3-git-send-email-jeff.layton@primarydata.com> X-Mailer: git-send-email 2.4.3 In-Reply-To: <1442493587-32499-1-git-send-email-jeff.layton@primarydata.com> References: <1442493587-32499-1-git-send-email-jeff.layton@primarydata.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP ...and move its EXPORT_SYMBOL just below the function. Signed-off-by: Jeff Layton --- fs/file_table.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/fs/file_table.c b/fs/file_table.c index 52cc6803c07a..8cfeaee6323f 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -261,6 +261,25 @@ void flush_delayed_fput(void) flush_delayed_work(&delayed_fput_work); } +/** + * fput - put a struct file reference + * @file: file of which to put the reference + * + * This function decrements the reference count for the struct file reference, + * and queues it up for destruction if the count goes to zero. In the case of + * most tasks we queue it to the task_work infrastructure, which will be run + * just before the task returns back to userspace. kthreads however never + * return to userspace, so for those we add them to a global list and schedule + * a delayed workqueue job to do the final cleanup work. + * + * Why not just do it synchronously? __fput can involve taking locks of all + * sorts, and doing it synchronously means that the callers must take extra care + * not to deadlock. That can be very difficult to ensure, so by deferring it + * until just before return to userland or to the workqueue, we sidestep that + * nastiness. Also, __fput can be quite stack intensive, so doing a final fput + * has the possibility of blowing up if we don't take steps to ensure that we + * have enough stack space to make it work. + */ void fput(struct file *file) { if (atomic_long_dec_and_test(&file->f_count)) { @@ -281,6 +300,7 @@ void fput(struct file *file) schedule_delayed_work(&delayed_fput_work, 1); } } +EXPORT_SYMBOL(fput); /* * synchronous analog of fput(); for kernel threads that might be needed @@ -299,7 +319,6 @@ void __fput_sync(struct file *file) } } -EXPORT_SYMBOL(fput); void put_filp(struct file *file) {