1 files changed, 315 insertions, 0 deletions
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
new file mode 100644
index 000000000..fc6c42eeb
--- /dev/null
+++ b/fs/afs/dynroot.c
@@ -0,0 +1,315 @@
+/* AFS dynamic root handling
+ *
+ * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/dns_resolver.h>
+#include "internal.h"
+
+const struct file_operations afs_dynroot_file_operations = {
+	.open		= dcache_dir_open,
+	.release	= dcache_dir_close,
+	.iterate_shared	= dcache_readdir,
+	.llseek		= dcache_dir_lseek,
+};
+
+/*
+ * Probe to see if a cell may exist.  This prevents positive dentries from
+ * being created unnecessarily.
+ */
+static int afs_probe_cell_name(struct dentry *dentry)
+{
+	struct afs_cell *cell;
+	const char *name = dentry->d_name.name;
+	size_t len = dentry->d_name.len;
+	int ret;
+
+	/* Names prefixed with a dot are R/W mounts. */
+	if (name[0] == '.') {
+		if (len == 1)
+			return -EINVAL;
+		name++;
+		len--;
+	}
+
+	cell = afs_lookup_cell_rcu(afs_d2net(dentry), name, len);
+	if (!IS_ERR(cell)) {
+		afs_put_cell(afs_d2net(dentry), cell);
+		return 0;
+	}
+
+	ret = dns_query("afsdb", name, len, "", NULL, NULL);
+	if (ret == -ENODATA)
+		ret = -EDESTADDRREQ;
+	return ret;
+}
+
+/*
+ * Try to auto mount the mountpoint with pseudo directory, if the autocell
+ * operation is setted.
+ */
+struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
+{
+	struct afs_vnode *vnode = AFS_FS_I(dir);
+	struct inode *inode;
+	int ret = -ENOENT;
+
+	_enter("%p{%pd}, {%x:%u}",
+	       dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
+
+	if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
+		goto out;
+
+	ret = afs_probe_cell_name(dentry);
+	if (ret < 0)
+		goto out;
+
+	inode = afs_iget_pseudo_dir(dir->i_sb, false);
+	if (IS_ERR(inode)) {
+		ret = PTR_ERR(inode);
+		goto out;
+	}
+
+	_leave("= %p", inode);
+	return inode;
+
+out:
+	_leave("= %d", ret);
+	return ret == -ENOENT ? NULL : ERR_PTR(ret);
+}
+
+/*
+ * Look up @cell in a dynroot directory.  This is a substitution for the
+ * local cell name for the net namespace.
+ */
+static struct dentry *afs_lookup_atcell(struct dentry *dentry)
+{
+	struct afs_cell *cell;
+	struct afs_net *net = afs_d2net(dentry);
+	struct dentry *ret;
+	unsigned int seq = 0;
+	char *name;
+	int len;
+
+	if (!net->ws_cell)
+		return ERR_PTR(-ENOENT);
+
+	ret = ERR_PTR(-ENOMEM);
+	name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
+	if (!name)
+		goto out_p;
+
+	rcu_read_lock();
+	do {
+		read_seqbegin_or_lock(&net->cells_lock, &seq);
+		cell = rcu_dereference_raw(net->ws_cell);
+		if (cell) {
+			len = cell->name_len;
+			memcpy(name, cell->name, len + 1);
+		}
+	} while (need_seqretry(&net->cells_lock, seq));
+	done_seqretry(&net->cells_lock, seq);
+	rcu_read_unlock();
+
+	ret = ERR_PTR(-ENOENT);
+	if (!cell)
+		goto out_n;
+
+	ret = lookup_one_len(name, dentry->d_parent, len);
+
+	/* We don't want to d_add() the @cell dentry here as we don't want to
+	 * the cached dentry to hide changes to the local cell name.
+	 */
+
+out_n:
+	kfree(name);
+out_p:
+	return ret;
+}
+
+/*
+ * Look up an entry in a dynroot directory.
+ */
+static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
+					 unsigned int flags)
+{
+	_enter("%pd", dentry);
+
+	ASSERTCMP(d_inode(dentry), ==, NULL);
+
+	if (flags & LOOKUP_CREATE)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	if (dentry->d_name.len >= AFSNAMEMAX) {
+		_leave(" = -ENAMETOOLONG");
+		return ERR_PTR(-ENAMETOOLONG);
+	}
+
+	if (dentry->d_name.len == 5 &&
+	    memcmp(dentry->d_name.name, "@cell", 5) == 0)
+		return afs_lookup_atcell(dentry);
+
+	return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
+}
+
+const struct inode_operations afs_dynroot_inode_operations = {
+	.lookup		= afs_dynroot_lookup,
+};
+
+/*
+ * Dirs in the dynamic root don't need revalidation.
+ */
+static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	return 1;
+}
+
+/*
+ * Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
+ * sleep)
+ * - called from dput() when d_count is going to 0.
+ * - return 1 to request dentry be unhashed, 0 otherwise
+ */
+static int afs_dynroot_d_delete(const struct dentry *dentry)
+{
+	return d_really_is_positive(dentry);
+}
+
+const struct dentry_operations afs_dynroot_dentry_operations = {
+	.d_revalidate	= afs_dynroot_d_revalidate,
+	.d_delete	= afs_dynroot_d_delete,
+	.d_release	= afs_d_release,
+	.d_automount	= afs_d_automount,
+};
+
+/*
+ * Create a manually added cell mount directory.
+ * - The caller must hold net->proc_cells_lock
+ */
+int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
+{
+	struct super_block *sb = net->dynroot_sb;
+	struct dentry *root, *subdir;
+	int ret;
+
+	if (!sb || atomic_read(&sb->s_active) == 0)
+		return 0;
+
+	/* Let the ->lookup op do the creation */
+	root = sb->s_root;
+	inode_lock(root->d_inode);
+	subdir = lookup_one_len(cell->name, root, cell->name_len);
+	if (IS_ERR(subdir)) {
+		ret = PTR_ERR(subdir);
+		goto unlock;
+	}
+
+	/* Note that we're retaining an extra ref on the dentry */
+	subdir->d_fsdata = (void *)1UL;
+	ret = 0;
+unlock:
+	inode_unlock(root->d_inode);
+	return ret;
+}
+
+/*
+ * Remove a manually added cell mount directory.
+ * - The caller must hold net->proc_cells_lock
+ */
+void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
+{
+	struct super_block *sb = net->dynroot_sb;
+	struct dentry *root, *subdir;
+
+	if (!sb || atomic_read(&sb->s_active) == 0)
+		return;
+
+	root = sb->s_root;
+	inode_lock(root->d_inode);
+
+	/* Don't want to trigger a lookup call, which will re-add the cell */
+	subdir = try_lookup_one_len(cell->name, root, cell->name_len);
+	if (IS_ERR_OR_NULL(subdir)) {
+		_debug("lookup %ld", PTR_ERR(subdir));
+		goto no_dentry;
+	}
+
+	_debug("rmdir %pd %u", subdir, d_count(subdir));
+
+	if (subdir->d_fsdata) {
+		_debug("unpin %u", d_count(subdir));
+		subdir->d_fsdata = NULL;
+		dput(subdir);
+	}
+	dput(subdir);
+no_dentry:
+	inode_unlock(root->d_inode);
+	_leave("");
+}
+
+/*
+ * Populate a newly created dynamic root with cell names.
+ */
+int afs_dynroot_populate(struct super_block *sb)
+{
+	struct afs_cell *cell;
+	struct afs_net *net = afs_sb2net(sb);
+	int ret;
+
+	if (mutex_lock_interruptible(&net->proc_cells_lock) < 0)
+		return -ERESTARTSYS;
+
+	net->dynroot_sb = sb;
+	hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
+		ret = afs_dynroot_mkdir(net, cell);
+		if (ret < 0)
+			goto error;
+	}
+
+	ret = 0;
+out:
+	mutex_unlock(&net->proc_cells_lock);
+	return ret;
+
+error:
+	net->dynroot_sb = NULL;
+	goto out;
+}
+
+/*
+ * When a dynamic root that's in the process of being destroyed, depopulate it
+ * of pinned directories.
+ */
+void afs_dynroot_depopulate(struct super_block *sb)
+{
+	struct afs_net *net = afs_sb2net(sb);
+	struct dentry *root = sb->s_root, *subdir, *tmp;
+
+	/* Prevent more subdirs from being created */
+	mutex_lock(&net->proc_cells_lock);
+	if (net->dynroot_sb == sb)
+		net->dynroot_sb = NULL;
+	mutex_unlock(&net->proc_cells_lock);
+
+	if (root) {
+		inode_lock(root->d_inode);
+
+		/* Remove all the pins for dirs created for manually added cells */
+		list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
+			if (subdir->d_fsdata) {
+				subdir->d_fsdata = NULL;
+				dput(subdir);
+			}
+		}
+
+		inode_unlock(root->d_inode);
+	}
+}