linux-ext4 - [PATCH 4/6] afs: Use RCU inode cache search for callback resolution [ver #2]

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Message-ID: <155620453952.4720.15231543377694604682.stgit@warthog.procyon.org.uk>
Date:   Thu, 25 Apr 2019 16:02:19 +0100
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     linux-afs@...ts.infradead.org, dhowells@...hat.com,
        linux-afs@...ts.infradead.org, linux-ext4@...r.kernel.org,
        linux-ntfs-dev@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 4/6] afs: Use RCU inode cache search for callback resolution
 [ver #2]

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@...hat.com>
cc: linux-afs@...ts.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();
 }
 
 /*