linux-kernel - [PATCH 2/4] fs: add a kerneldoc header to fput

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Date:	Mon, 14 Sep 2015 09:45:53 -0400
From:	Jeff Layton <jlayton@...chiereds.net>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	bfields@...ldses.org, linux-nfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/4] fs: add a kerneldoc header to fput

...and move its EXPORT_SYMBOL just below the function.

Signed-off-by: Jeff Layton <jeff.layton@...marydata.com>
---
 fs/file_table.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/fs/file_table.c b/fs/file_table.c
index f4833af62eae..d63f4a399d39 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -260,6 +260,21 @@ 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 work of putting them.
+ *
+ * Why not just do it synchronously? __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)) {
@@ -280,6 +295,7 @@ 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
@@ -298,7 +314,6 @@ void __fput_sync(struct file *file)
 	}
 }
 
-EXPORT_SYMBOL(fput);
 
 void put_filp(struct file *file)
 {
-- 
2.4.3

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