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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
---
fs/file_table.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
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)) {
--
2.4.3
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