[v6,02/19] fs: have flush_delayed_fput flush the workqueue job
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Message ID 1445362432-18869-3-git-send-email-jeff.layton@primarydata.com
State New
Headers show

Commit Message

Jeff Layton Oct. 20, 2015, 5:33 p.m. UTC
I think there's a potential race in flush_delayed_fput. A kthread does
an fput() and that file gets added to the list and the delayed work is
scheduled. More than 1 jiffy passes, and the workqueue thread picks up
the work and starts running it. Then the kthread calls
flush_delayed_work.  It sees that the list is empty and returns
immediately, even though the __fput for its file may not have run yet.

Close this by making flush_delayed_fput use flush_delayed_work instead,
which should immediately schedule the work to run if it's not already,
and block until the workqueue job completes.

Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
 fs/file_table.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

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diff --git a/fs/file_table.c b/fs/file_table.c
index ad17e05ebf95..52cc6803c07a 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -244,6 +244,8 @@  static void ____fput(struct callback_head *work)
 	__fput(container_of(work, struct file, f_u.fu_rcuhead));
+static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
  * If kernel thread really needs to have the final fput() it has done
  * to complete, call this.  The only user right now is the boot - we
@@ -256,11 +258,9 @@  static void ____fput(struct callback_head *work)
 void flush_delayed_fput(void)
-	delayed_fput(NULL);
+	flush_delayed_work(&delayed_fput_work);
-static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
 void fput(struct file *file)
 	if (atomic_long_dec_and_test(&file->f_count)) {