ceph: drop negative child dentries before try pruning inode's alias

Negative child dentry holds reference on inode's alias, it makes
d_prune_aliases() do nothing.

Cc: stable@vger.kernel.org
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 38 insertions, 4 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index ab69dcb70e8a..1b468250e947 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1440,6 +1440,29 @@ static int __close_session(struct ceph_mds_client *mdsc,
         return request_close_session(mdsc, session);
 }
 
+static bool drop_negative_children(struct dentry *dentry)
+{
+        struct dentry *child;
+        bool all_negative = true;
+
+        if (!d_is_dir(dentry))
+                goto out;
+
+        spin_lock(&dentry->d_lock);
+        list_for_each_entry(child, &dentry->d_subdirs, d_child) {
+                if (d_really_is_positive(child)) {
+                        all_negative = false;
+                        break;
+                }
+        }
+        spin_unlock(&dentry->d_lock);
+
+        if (all_negative)
+                shrink_dcache_parent(dentry);
+out:
+        return all_negative;
+}
+
 /*
  * Trim old(er) caps.
  *
@@ -1490,16 +1513,27 @@ static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg)
         if ((used | wanted) & ~oissued & mine)
                 goto out;   /* we need these caps */
 
-        session->s_trim_caps--;
         if (oissued) {
                 /* we aren't the only cap.. just remove us */
                 __ceph_remove_cap(cap, true);
+                session->s_trim_caps--;
         } else {
+                struct dentry *dentry;
                 /* try dropping referring dentries */
                 spin_unlock(&ci->i_ceph_lock);
-                d_prune_aliases(inode);
-                dout("trim_caps_cb %p cap %p  pruned, count now %d\n",
-                     inode, cap, atomic_read(&inode->i_count));
+                dentry = d_find_any_alias(inode);
+                if (dentry && drop_negative_children(dentry)) {
+                        int count;
+                        dput(dentry);
+                        d_prune_aliases(inode);
+                        count = atomic_read(&inode->i_count);
+                        if (count == 1)
+                                session->s_trim_caps--;
+                        dout("trim_caps_cb %p cap %p pruned, count now %d\n",
+                             inode, cap, count);
+                } else {
+                        dput(dentry);
+                }
                 return 0;
         }