From: Jeff Layton <jlayton@poochiereds.net>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: bfields@fieldses.org, linux-nfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/4] fs: have flush_delayed_fput flush the workqueue job
Date: Mon, 14 Sep 2015 09:45:52 -0400 [thread overview]
Message-ID: <1442238355-8203-2-git-send-email-jeff.layton@primarydata.com> (raw)
In-Reply-To: <1442238355-8203-1-git-send-email-jeff.layton@primarydata.com>
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.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
---
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 7f9d407c7595..f4833af62eae 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -243,6 +243,8 @@ 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
@@ -255,11 +257,9 @@ 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
next prev parent reply other threads:[~2015-09-14 13:46 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-14 13:45 [PATCH 0/4] fs: allow userland tasks to use delayed_fput infrastructure Jeff Layton
2015-09-14 13:45 ` Jeff Layton
2015-09-14 13:45 ` Jeff Layton [this message]
2015-09-14 13:45 ` [PATCH 2/4] fs: add a kerneldoc header to fput Jeff Layton
2015-09-14 13:45 ` [PATCH 3/4] fs: add fput_queue Jeff Layton
2015-09-14 13:45 ` Jeff Layton
2015-09-14 14:15 ` Al Viro
2015-09-14 14:19 ` Jeff Layton
2015-09-14 16:39 ` Al Viro
2015-09-14 17:30 ` Jeff Layton
2015-09-14 13:45 ` [PATCH 4/4] fs: export flush_delayed_fput Jeff Layton
2015-09-14 14:48 ` [PATCH 0/4] fs: allow userland tasks to use delayed_fput infrastructure J. Bruce Fields
2015-09-14 14:48 ` J. Bruce Fields
2015-09-14 15:21 ` Jeff Layton
2015-09-14 15:21 ` Jeff Layton
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