linux-kernel - [PATCH 4.9 077/107] fuse: umount should wait for all requests

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Message-Id: <20180903165641.035204534@linuxfoundation.org>
Date:   Mon,  3 Sep 2018 18:56:41 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Miklos Szeredi <mszeredi@...hat.com>
Subject: [PATCH 4.9 077/107] fuse: umount should wait for all requests

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@...hat.com>

commit b8f95e5d13f5f0191dcb4b9113113d241636e7cb upstream.

fuse_abort_conn() does not guarantee that all async requests have actually
finished aborting (i.e. their ->end() function is called).  This could
actually result in still used inodes after umount.

Add a helper to wait until all requests are fully done.  This is done by
looking at the "num_waiting" counter.  When this counter drops to zero, we
can be sure that no more requests are outstanding.

Fixes: 0d8e84b0432b ("fuse: simplify request abort")
Cc: <stable@...r.kernel.org> # v4.2
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/fuse/dev.c    |   23 +++++++++++++++++++----
 fs/fuse/fuse_i.h |    1 +
 fs/fuse/inode.c  |    2 ++
 3 files changed, 22 insertions(+), 4 deletions(-)

--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -130,6 +130,16 @@ static bool fuse_block_alloc(struct fuse
 	return !fc->initialized || (for_background && fc->blocked);
 }
 
+static void fuse_drop_waiting(struct fuse_conn *fc)
+{
+	if (fc->connected) {
+		atomic_dec(&fc->num_waiting);
+	} else if (atomic_dec_and_test(&fc->num_waiting)) {
+		/* wake up aborters */
+		wake_up_all(&fc->blocked_waitq);
+	}
+}
+
 static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
 				       bool for_background)
 {
@@ -170,7 +180,7 @@ static struct fuse_req *__fuse_get_req(s
 	return req;
 
  out:
-	atomic_dec(&fc->num_waiting);
+	fuse_drop_waiting(fc);
 	return ERR_PTR(err);
 }
 
@@ -277,7 +287,7 @@ void fuse_put_request(struct fuse_conn *
 
 		if (test_bit(FR_WAITING, &req->flags)) {
 			__clear_bit(FR_WAITING, &req->flags);
-			atomic_dec(&fc->num_waiting);
+			fuse_drop_waiting(fc);
 		}
 
 		if (req->stolen_file)
@@ -363,7 +373,7 @@ static void request_end(struct fuse_conn
 	struct fuse_iqueue *fiq = &fc->iq;
 
 	if (test_and_set_bit(FR_FINISHED, &req->flags))
-		goto out_put_req;
+		goto put_request;
 
 	spin_lock(&fiq->waitq.lock);
 	list_del_init(&req->intr_entry);
@@ -393,7 +403,7 @@ static void request_end(struct fuse_conn
 	wake_up(&req->waitq);
 	if (req->end)
 		req->end(fc, req);
-out_put_req:
+put_request:
 	fuse_put_request(fc, req);
 }
 
@@ -2135,6 +2145,11 @@ void fuse_abort_conn(struct fuse_conn *f
 }
 EXPORT_SYMBOL_GPL(fuse_abort_conn);
 
+void fuse_wait_aborted(struct fuse_conn *fc)
+{
+	wait_event(fc->blocked_waitq, atomic_read(&fc->num_waiting) == 0);
+}
+
 int fuse_dev_release(struct inode *inode, struct file *file)
 {
 	struct fuse_dev *fud = fuse_get_dev(file);
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -854,6 +854,7 @@ void fuse_request_send_background_locked
 
 /* Abort all requests */
 void fuse_abort_conn(struct fuse_conn *fc);
+void fuse_wait_aborted(struct fuse_conn *fc);
 
 /**
  * Invalidate inode attributes
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -405,6 +405,8 @@ static void fuse_put_super(struct super_
 	fuse_send_destroy(fc);
 
 	fuse_abort_conn(fc);
+	fuse_wait_aborted(fc);
+
 	mutex_lock(&fuse_mutex);
 	list_del(&fc->entry);
 	fuse_ctl_remove_conn(fc);