[PATCH 4.14 122/165] fuse: umount should wait for all requests

[Greg Kroah-Hartman]

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

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

From: Miklos Szeredi <mszer...@redhat.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: <sta...@vger.kernel.org> # v4.2
Signed-off-by: Miklos Szeredi <mszer...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.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
@@ -131,6 +131,16 @@ 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)
 {
@@ -171,7 +181,7 @@ static struct fuse_req *__fuse_get_req(s
        return req;
 
  out:
-       atomic_dec(&fc->num_waiting);
+       fuse_drop_waiting(fc);
        return ERR_PTR(err);
 }
 
@@ -278,7 +288,7 @@ 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)
@@ -364,7 +374,7 @@ 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);
 }
 
@@ -2141,6 +2151,11 @@ 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
@@ -852,6 +852,7 @@ 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
@@ -400,6 +400,8 @@ 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);