Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley
 Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United
 Kingdom.
 Registered in England and Wales under Company Registration No. 3798903
Subject: [RFC PATCH 4/6] afs: Use RCU inode cache search for callback
 resolution
From:   David Howells <dhowells@redhat.com>
To:     viro@zeniv.linux.org.uk
Cc:     linux-afs@lists.infradead.org, dhowells@redhat.com,
        linux-afs@lists.infradead.org, linux-ext4@vger.kernel.org,
        linux-ntfs-dev@lists.sourceforge.net,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Thu, 18 Apr 2019 15:06:35 +0100
Message-ID: <155559639544.21702.12655956327932453417.stgit@warthog.procyon.org.uk>
In-Reply-To: <155559635133.21702.4737487773869377967.stgit@warthog.procyon.org.uk>
References: <155559635133.21702.4737487773869377967.stgit@warthog.procyon.org.uk>
User-Agent: StGit/unknown-version
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Search the inode cache under "RCU conditions" when trying to find a vnode
to break the callback on.  We don't want to be taking the icache lock if we
can avoid it.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
---

 fs/afs/callback.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 128f2dbe256a..3d0280d4fbf0 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -251,6 +251,7 @@ static void afs_break_one_callback(struct afs_server *server,
 	struct afs_vnode *vnode;
 	struct inode *inode;
 
+	rcu_read_lock();
 	read_lock(&server->cb_break_lock);
 	hlist_for_each_entry(vi, &server->cb_volumes, srv_link) {
 		if (vi->vid < fid->vid)
@@ -284,18 +285,23 @@ static void afs_break_one_callback(struct afs_server *server,
 		} else {
 			data.volume = NULL;
 			data.fid = *fid;
-			inode = ilookup5_nowait(cbi->sb, fid->vnode,
-						afs_iget5_test, &data);
+
+			/* See if we can find a matching inode - even an I_NEW
+			 * inode needs to be marked as it can have its callback
+			 * broken before we finish setting up the local inode.
+			 */
+			inode = find_inode_rcu(cbi->sb, fid->vnode,
+					       afs_iget5_test, &data);
 			if (inode) {
 				vnode = AFS_FS_I(inode);
 				afs_break_callback(vnode);
-				iput(inode);
 			}
 		}
 	}
 
 out:
 	read_unlock(&server->cb_break_lock);
+	rcu_read_unlock();
 }
 
 /*