From 565277f63c616e11c37309a1e98c052d18ebbb55 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Mon, 15 Oct 2007 18:17:53 -0400
Subject: NFS: Fix a race in sillyrename

lookup() and sillyrename() can race one another because the sillyrename()
completion cannot take the parent directory's inode->i_mutex since the
latter may be held by whoever is calling dput().

We therefore have little option but to add extra locking to ensure that
nfs_lookup() and nfs_atomic_open() do not race with the sillyrename
completion.
If somebody has looked up the sillyrenamed file in the meantime, we just
transfer the sillydelete information to the new dentry.

Please refer to the bug-report at
	http://bugzilla.linux-nfs.org/show_bug.cgi?id=150

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---
 fs/nfs/nfs4proc.c | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'fs/nfs/nfs4proc.c')

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index cb99fd90a9a..2cb3b8b71ee 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1372,6 +1372,7 @@ out_close:
 struct dentry *
 nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 {
+	struct dentry *parent;
 	struct path path = {
 		.mnt = nd->mnt,
 		.dentry = dentry,
@@ -1394,6 +1395,9 @@ nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 	cred = rpcauth_lookupcred(NFS_CLIENT(dir)->cl_auth, 0);
 	if (IS_ERR(cred))
 		return (struct dentry *)cred;
+	parent = dentry->d_parent;
+	/* Protect against concurrent sillydeletes */
+	nfs_block_sillyrename(parent);
 	state = nfs4_do_open(dir, &path, nd->intent.open.flags, &attr, cred);
 	put_rpccred(cred);
 	if (IS_ERR(state)) {
@@ -1401,12 +1405,14 @@ nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 			d_add(dentry, NULL);
 			nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
 		}
+		nfs_unblock_sillyrename(parent);
 		return (struct dentry *)state;
 	}
 	res = d_add_unique(dentry, igrab(state->inode));
 	if (res != NULL)
 		path.dentry = res;
 	nfs_set_verifier(path.dentry, nfs_save_change_attribute(dir));
+	nfs_unblock_sillyrename(parent);
 	nfs4_intent_set_file(nd, &path, state);
 	return res;
 }
-- 
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