Return-Path: Received: from mail-yk0-f181.google.com ([209.85.160.181]:33490 "EHLO mail-yk0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751906AbbIQMj5 (ORCPT ); Thu, 17 Sep 2015 08:39:57 -0400 Received: by ykft14 with SMTP id t14so15186687ykf.0 for ; Thu, 17 Sep 2015 05:39:56 -0700 (PDT) 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 3/4] fs: add fput_queue Date: Thu, 17 Sep 2015 08:39:46 -0400 Message-Id: <1442493587-32499-4-git-send-email-jeff.layton@primarydata.com> 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-nfs-owner@vger.kernel.org List-ID: When nfsd caches a file, we want to be able to close it down in advance of setlease attempts. Setting a lease is generally done at the behest of userland, so we need a mechanism to ensure that a userland task can completely close a file without having to return back to userspace. To do this, we borrow the delayed_fput infrastructure that kthreads use. fput_queue will queue to the delayed_fput list if the last reference was put. The caller can then call flush_delayed_fput to ensure that the files are completely closed before proceeding. Signed-off-by: Jeff Layton --- fs/file_table.c | 27 +++++++++++++++++++++++++++ include/linux/file.h | 1 + 2 files changed, 28 insertions(+) diff --git a/fs/file_table.c b/fs/file_table.c index 8cfeaee6323f..95361d2b8a08 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -302,6 +302,33 @@ void fput(struct file *file) } EXPORT_SYMBOL(fput); +/** + * fput_queue - do an fput without using task_work + * @file: file of which to put the reference + * + * When fput is called in the context of a userland process, it'll queue the + * actual work (__fput()) to be done just before returning to userland. In some + * cases however, we need to ensure that the __fput runs before that point. + * There is no safe way to flush work that has been queued via task_work_add + * however, so to do this we borrow the delayed_fput infrastructure that + * kthreads use. The userland process can use fput_queue() on one or more + * struct files and then call flush_delayed_fput() to ensure that they are + * completely closed before proceeding. + * + * Returns true if the final fput was done, false otherwise. The caller can + * use this to determine whether to flush_delayed_fput afterward. + */ +bool fput_queue(struct file *file) +{ + if (atomic_long_dec_and_test(&file->f_count)) { + if (llist_add(&file->f_u.fu_llist, &delayed_fput_list)) + schedule_delayed_work(&delayed_fput_work, 1); + return true; + } + return false; +} +EXPORT_SYMBOL(fput_queue); + /* * synchronous analog of fput(); for kernel threads that might be needed * in some umount() (and thus can't use flush_delayed_fput() without diff --git a/include/linux/file.h b/include/linux/file.h index f87d30882a24..f9308c9a0746 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -12,6 +12,7 @@ struct file; extern void fput(struct file *); +extern bool fput_queue(struct file *); struct file_operations; struct vfsmount; -- 2.4.3