nfs: store devname at disconnected NFS roots

part 2: make sure that disconnected roots have corresponding mnt_devname
values stashed into them.

Have nfs*_get_root() stuff a copy of devname into ->d_fsdata of the
found root, provided that it is disconnected.

Have ->d_release() free it when dentry goes away.

Have the places where NFS uses ->d_fsdata for sillyrename (and that
can *never* happen to a disconnected root - dentry will be attached
to its parent) free old devname copies if they find those.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/nfs/dir.c

@@ -1169,11 +1169,23 @@ static void nfs_dentry_iput(struct dentry *dentry, struct inode *inode)
 	iput(inode);
 }
 
+static void nfs_d_release(struct dentry *dentry)
+{
+	/* free cached devname value, if it survived that far */
+	if (unlikely(dentry->d_fsdata)) {
+		if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
+			WARN_ON(1);
+		else
+			kfree(dentry->d_fsdata);
+	}
+}
+
 const struct dentry_operations nfs_dentry_operations = {
 	.d_revalidate	= nfs_lookup_revalidate,
 	.d_delete	= nfs_dentry_delete,
 	.d_iput		= nfs_dentry_iput,
 	.d_automount	= nfs_d_automount,
+	.d_release	= nfs_d_release,
 };
 
 static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, struct nameidata *nd)
@@ -1248,6 +1260,7 @@ const struct dentry_operations nfs4_dentry_operations = {
 	.d_delete	= nfs_dentry_delete,
 	.d_iput		= nfs_dentry_iput,
 	.d_automount	= nfs_d_automount,
+	.d_release	= nfs_d_release,
 };
 
 /*

fs/nfs/getroot.c

@@ -82,12 +82,18 @@ struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
 	struct nfs_fsinfo fsinfo;
 	struct dentry *ret;
 	struct inode *inode;
+	void *name = kstrdup(devname, GFP_KERNEL);
 	int error;
 
+	if (!name)
+		return ERR_PTR(-ENOMEM);
+
 	/* get the actual root for this mount */
 	fsinfo.fattr = nfs_alloc_fattr();
-	if (fsinfo.fattr == NULL)
+	if (fsinfo.fattr == NULL) {
+		kfree(name);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 	if (error < 0) {
@@ -120,7 +126,15 @@ struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
 	}
 
 	security_d_instantiate(ret, inode);
+	spin_lock(&ret->d_lock);
+	if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
+		ret->d_fsdata = name;
+		name = NULL;
+	}
+	spin_unlock(&ret->d_lock);
 out:
+	if (name)
+		kfree(name);
 	nfs_free_fattr(fsinfo.fattr);
 	return ret;
 }
@@ -177,21 +191,28 @@ struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh,
 	struct nfs_fattr *fattr = NULL;
 	struct dentry *ret;
 	struct inode *inode;
+	void *name = kstrdup(devname, GFP_KERNEL);
 	int error;
 
 	dprintk("--> nfs4_get_root()\n");
 
+	if (!name)
+		return ERR_PTR(-ENOMEM);
+
 	/* get the info about the server and filesystem */
 	error = nfs4_server_capabilities(server, mntfh);
 	if (error < 0) {
 		dprintk("nfs_get_root: getcaps error = %d\n",
 			-error);
+		kfree(name);
 		return ERR_PTR(error);
 	}
 
 	fattr = nfs_alloc_fattr();
-	if (fattr == NULL)
-		return ERR_PTR(-ENOMEM);;
+	if (fattr == NULL) {
+		kfree(name);
+		return ERR_PTR(-ENOMEM);
+	}
 
 	/* get the actual root for this mount */
 	error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr);
@@ -225,8 +246,15 @@ struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh,
 	}
 
 	security_d_instantiate(ret, inode);
-
+	spin_lock(&ret->d_lock);
+	if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
+		ret->d_fsdata = name;
+		name = NULL;
+	}
+	spin_unlock(&ret->d_lock);
 out:
+	if (name)
+		kfree(name);
 	nfs_free_fattr(fattr);
 	dprintk("<-- nfs4_get_root()\n");
 	return ret;

fs/nfs/unlink.c

@@ -148,6 +148,7 @@ static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct n
 	alias = d_lookup(parent, &data->args.name);
 	if (alias != NULL) {
 		int ret = 0;
+		void *devname_garbage = NULL;
 
 		/*
 		 * Hey, we raced with lookup... See if we need to transfer
@@ -157,6 +158,7 @@ static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct n
 		spin_lock(&alias->d_lock);
 		if (alias->d_inode != NULL &&
 		    !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
+			devname_garbage = alias->d_fsdata;
 			alias->d_fsdata = data;
 			alias->d_flags |= DCACHE_NFSFS_RENAMED;
 			ret = 1;
@@ -164,6 +166,13 @@ static int nfs_do_call_unlink(struct dentry *parent, struct inode *dir, struct n
 		spin_unlock(&alias->d_lock);
 		nfs_dec_sillycount(dir);
 		dput(alias);
+		/*
+		 * If we'd displaced old cached devname, free it.  At that
+		 * point dentry is definitely not a root, so we won't need
+		 * that anymore.
+		 */
+		if (devname_garbage)
+			kfree(devname_garbage);
 		return ret;
 	}
 	data->dir = igrab(dir);
@@ -252,6 +261,7 @@ nfs_async_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct nfs_unlinkdata *data;
 	int status = -ENOMEM;
+	void *devname_garbage = NULL;
 
 	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (data == NULL)
@@ -269,8 +279,16 @@ nfs_async_unlink(struct inode *dir, struct dentry *dentry)
 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
 		goto out_unlock;
 	dentry->d_flags |= DCACHE_NFSFS_RENAMED;
+	devname_garbage = dentry->d_fsdata;
 	dentry->d_fsdata = data;
 	spin_unlock(&dentry->d_lock);
+	/*
+	 * If we'd displaced old cached devname, free it.  At that
+	 * point dentry is definitely not a root, so we won't need
+	 * that anymore.
+	 */
+	if (devname_garbage)
+		kfree(devname_garbage);
 	return 0;
 out_unlock:
 	spin_unlock(&dentry->d_lock);
@@ -299,6 +317,7 @@ nfs_complete_unlink(struct dentry *dentry, struct inode *inode)
 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
 		dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
 		data = dentry->d_fsdata;
+		dentry->d_fsdata = NULL;
 	}
 	spin_unlock(&dentry->d_lock);
 
@@ -315,6 +334,7 @@ nfs_cancel_async_unlink(struct dentry *dentry)
 		struct nfs_unlinkdata *data = dentry->d_fsdata;
 
 		dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
+		dentry->d_fsdata = NULL;
 		spin_unlock(&dentry->d_lock);
 		nfs_free_unlinkdata(data);
 		return;