linux-kernel - [PATCH 4.9 013/177] ceph: drop negative child dentries before try pruning inodes alias

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Message-Id: <20171218152910.520310265@linuxfoundation.org>
Date:   Mon, 18 Dec 2017 16:47:16 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Yan, Zheng" <zyan@...hat.com>,
        Jeff Layton <jlayton@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>
Subject: [PATCH 4.9 013/177] ceph: drop negative child dentries before try pruning inodes alias

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

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

From: Yan, Zheng <zyan@...hat.com>

commit 040d786032bf59002d374b86d75b04d97624005c upstream.

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

Signed-off-by: "Yan, Zheng" <zyan@...hat.com>
Reviewed-by: Jeff Layton <jlayton@...hat.com>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ceph/mds_client.c |   42 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 38 insertions(+), 4 deletions(-)

--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1396,6 +1396,29 @@ static int __close_session(struct ceph_m
 	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.
  *
@@ -1441,16 +1464,27 @@ static int trim_caps_cb(struct inode *in
 	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;
 	}