Return-Path: Received: from mail-qk0-f172.google.com ([209.85.220.172]:34175 "EHLO mail-qk0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753333AbbKQLxV (ORCPT ); Tue, 17 Nov 2015 06:53:21 -0500 Received: by qkfo3 with SMTP id o3so1683771qkf.1 for ; Tue, 17 Nov 2015 03:53:20 -0800 (PST) From: Jeff Layton To: bfields@fieldses.org, trond.myklebust@primarydata.com Cc: linux-nfs@vger.kernel.org, Eric Paris , Alexander Viro , linux-fsdevel@vger.kernel.org Subject: [PATCH v1 03/38] fs: add a kerneldoc header to fput Date: Tue, 17 Nov 2015 06:52:25 -0500 Message-Id: <1447761180-4250-4-git-send-email-jeff.layton@primarydata.com> In-Reply-To: <1447761180-4250-1-git-send-email-jeff.layton@primarydata.com> References: <1447761180-4250-1-git-send-email-jeff.layton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: ...and move its EXPORT_SYMBOL just below the function. Cc: Al Viro 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) { -- 2.4.3