301 lines
6.6 KiB
C
301 lines
6.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* AFS dynamic root handling
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*
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* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/fs.h>
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#include <linux/namei.h>
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#include <linux/dns_resolver.h>
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#include "internal.h"
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/*
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* Probe to see if a cell may exist. This prevents positive dentries from
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* being created unnecessarily.
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*/
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static int afs_probe_cell_name(struct dentry *dentry)
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{
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struct afs_cell *cell;
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struct afs_net *net = afs_d2net(dentry);
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const char *name = dentry->d_name.name;
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size_t len = dentry->d_name.len;
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int ret;
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/* Names prefixed with a dot are R/W mounts. */
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if (name[0] == '.') {
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if (len == 1)
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return -EINVAL;
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name++;
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len--;
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}
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cell = afs_lookup_cell_rcu(net, name, len);
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if (!IS_ERR(cell)) {
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afs_put_cell(net, cell);
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return 0;
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}
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ret = dns_query(net->net, "afsdb", name, len, "srv=1",
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NULL, NULL, false);
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if (ret == -ENODATA)
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ret = -EDESTADDRREQ;
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return ret;
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}
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/*
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* Try to auto mount the mountpoint with pseudo directory, if the autocell
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* operation is setted.
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*/
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struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir)
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{
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struct afs_vnode *vnode = AFS_FS_I(dir);
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struct inode *inode;
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int ret = -ENOENT;
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_enter("%p{%pd}, {%llx:%llu}",
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dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
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if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
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goto out;
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ret = afs_probe_cell_name(dentry);
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if (ret < 0)
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goto out;
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inode = afs_iget_pseudo_dir(dir->i_sb, false);
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if (IS_ERR(inode)) {
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ret = PTR_ERR(inode);
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goto out;
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}
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_leave("= %p", inode);
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return inode;
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out:
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_leave("= %d", ret);
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return ret == -ENOENT ? NULL : ERR_PTR(ret);
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}
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/*
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* Look up @cell in a dynroot directory. This is a substitution for the
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* local cell name for the net namespace.
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*/
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static struct dentry *afs_lookup_atcell(struct dentry *dentry)
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{
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struct afs_cell *cell;
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struct afs_net *net = afs_d2net(dentry);
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struct dentry *ret;
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unsigned int seq = 0;
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char *name;
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int len;
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if (!net->ws_cell)
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return ERR_PTR(-ENOENT);
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ret = ERR_PTR(-ENOMEM);
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name = kmalloc(AFS_MAXCELLNAME + 1, GFP_KERNEL);
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if (!name)
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goto out_p;
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rcu_read_lock();
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do {
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read_seqbegin_or_lock(&net->cells_lock, &seq);
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cell = rcu_dereference_raw(net->ws_cell);
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if (cell) {
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len = cell->name_len;
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memcpy(name, cell->name, len + 1);
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}
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} while (need_seqretry(&net->cells_lock, seq));
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done_seqretry(&net->cells_lock, seq);
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rcu_read_unlock();
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ret = ERR_PTR(-ENOENT);
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if (!cell)
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goto out_n;
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ret = lookup_one_len(name, dentry->d_parent, len);
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/* We don't want to d_add() the @cell dentry here as we don't want to
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* the cached dentry to hide changes to the local cell name.
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*/
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out_n:
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kfree(name);
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out_p:
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return ret;
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}
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/*
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* Look up an entry in a dynroot directory.
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*/
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static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
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unsigned int flags)
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{
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_enter("%pd", dentry);
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ASSERTCMP(d_inode(dentry), ==, NULL);
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if (dentry->d_name.len >= AFSNAMEMAX) {
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_leave(" = -ENAMETOOLONG");
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return ERR_PTR(-ENAMETOOLONG);
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}
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if (dentry->d_name.len == 5 &&
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memcmp(dentry->d_name.name, "@cell", 5) == 0)
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return afs_lookup_atcell(dentry);
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return d_splice_alias(afs_try_auto_mntpt(dentry, dir), dentry);
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}
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const struct inode_operations afs_dynroot_inode_operations = {
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.lookup = afs_dynroot_lookup,
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};
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/*
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* Dirs in the dynamic root don't need revalidation.
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*/
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static int afs_dynroot_d_revalidate(struct dentry *dentry, unsigned int flags)
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{
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return 1;
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}
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/*
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* Allow the VFS to enquire as to whether a dentry should be unhashed (mustn't
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* sleep)
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* - called from dput() when d_count is going to 0.
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* - return 1 to request dentry be unhashed, 0 otherwise
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*/
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static int afs_dynroot_d_delete(const struct dentry *dentry)
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{
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return d_really_is_positive(dentry);
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}
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const struct dentry_operations afs_dynroot_dentry_operations = {
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.d_revalidate = afs_dynroot_d_revalidate,
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.d_delete = afs_dynroot_d_delete,
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.d_release = afs_d_release,
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.d_automount = afs_d_automount,
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};
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/*
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* Create a manually added cell mount directory.
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* - The caller must hold net->proc_cells_lock
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*/
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int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
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{
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struct super_block *sb = net->dynroot_sb;
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struct dentry *root, *subdir;
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int ret;
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if (!sb || atomic_read(&sb->s_active) == 0)
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return 0;
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/* Let the ->lookup op do the creation */
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root = sb->s_root;
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inode_lock(root->d_inode);
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subdir = lookup_one_len(cell->name, root, cell->name_len);
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if (IS_ERR(subdir)) {
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ret = PTR_ERR(subdir);
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goto unlock;
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}
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/* Note that we're retaining an extra ref on the dentry */
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subdir->d_fsdata = (void *)1UL;
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ret = 0;
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unlock:
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inode_unlock(root->d_inode);
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return ret;
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}
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/*
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* Remove a manually added cell mount directory.
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* - The caller must hold net->proc_cells_lock
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*/
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void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
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{
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struct super_block *sb = net->dynroot_sb;
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struct dentry *root, *subdir;
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if (!sb || atomic_read(&sb->s_active) == 0)
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return;
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root = sb->s_root;
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inode_lock(root->d_inode);
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/* Don't want to trigger a lookup call, which will re-add the cell */
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subdir = try_lookup_one_len(cell->name, root, cell->name_len);
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if (IS_ERR_OR_NULL(subdir)) {
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_debug("lookup %ld", PTR_ERR(subdir));
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goto no_dentry;
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}
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_debug("rmdir %pd %u", subdir, d_count(subdir));
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if (subdir->d_fsdata) {
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_debug("unpin %u", d_count(subdir));
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subdir->d_fsdata = NULL;
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dput(subdir);
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}
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dput(subdir);
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no_dentry:
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inode_unlock(root->d_inode);
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_leave("");
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}
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/*
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* Populate a newly created dynamic root with cell names.
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*/
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int afs_dynroot_populate(struct super_block *sb)
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{
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struct afs_cell *cell;
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struct afs_net *net = afs_sb2net(sb);
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int ret;
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mutex_lock(&net->proc_cells_lock);
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net->dynroot_sb = sb;
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hlist_for_each_entry(cell, &net->proc_cells, proc_link) {
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ret = afs_dynroot_mkdir(net, cell);
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if (ret < 0)
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goto error;
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}
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ret = 0;
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out:
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mutex_unlock(&net->proc_cells_lock);
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return ret;
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error:
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net->dynroot_sb = NULL;
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goto out;
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}
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/*
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* When a dynamic root that's in the process of being destroyed, depopulate it
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* of pinned directories.
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*/
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void afs_dynroot_depopulate(struct super_block *sb)
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{
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struct afs_net *net = afs_sb2net(sb);
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struct dentry *root = sb->s_root, *subdir, *tmp;
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/* Prevent more subdirs from being created */
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mutex_lock(&net->proc_cells_lock);
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if (net->dynroot_sb == sb)
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net->dynroot_sb = NULL;
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mutex_unlock(&net->proc_cells_lock);
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inode_lock(root->d_inode);
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/* Remove all the pins for dirs created for manually added cells */
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list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
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if (subdir->d_fsdata) {
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subdir->d_fsdata = NULL;
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dput(subdir);
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}
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}
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inode_unlock(root->d_inode);
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}
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