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393 lines
8.7 KiB
393 lines
8.7 KiB
// 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 ([email protected]) |
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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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static atomic_t afs_autocell_ino; |
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/* |
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* iget5() comparator for inode created by autocell operations |
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* |
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* These pseudo inodes don't match anything. |
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*/ |
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static int afs_iget5_pseudo_test(struct inode *inode, void *opaque) |
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{ |
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return 0; |
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} |
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/* |
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* iget5() inode initialiser |
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*/ |
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static int afs_iget5_pseudo_set(struct inode *inode, void *opaque) |
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{ |
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struct afs_super_info *as = AFS_FS_S(inode->i_sb); |
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struct afs_vnode *vnode = AFS_FS_I(inode); |
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struct afs_fid *fid = opaque; |
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vnode->volume = as->volume; |
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vnode->fid = *fid; |
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inode->i_ino = fid->vnode; |
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inode->i_generation = fid->unique; |
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return 0; |
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} |
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/* |
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* Create an inode for a dynamic root directory or an autocell dynamic |
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* automount dir. |
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*/ |
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struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root) |
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{ |
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struct afs_super_info *as = AFS_FS_S(sb); |
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struct afs_vnode *vnode; |
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struct inode *inode; |
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struct afs_fid fid = {}; |
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_enter(""); |
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if (as->volume) |
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fid.vid = as->volume->vid; |
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if (root) { |
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fid.vnode = 1; |
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fid.unique = 1; |
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} else { |
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fid.vnode = atomic_inc_return(&afs_autocell_ino); |
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fid.unique = 0; |
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} |
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inode = iget5_locked(sb, fid.vnode, |
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afs_iget5_pseudo_test, afs_iget5_pseudo_set, &fid); |
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if (!inode) { |
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_leave(" = -ENOMEM"); |
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return ERR_PTR(-ENOMEM); |
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} |
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_debug("GOT INODE %p { ino=%lu, vl=%llx, vn=%llx, u=%x }", |
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inode, inode->i_ino, fid.vid, fid.vnode, fid.unique); |
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vnode = AFS_FS_I(inode); |
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/* there shouldn't be an existing inode */ |
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BUG_ON(!(inode->i_state & I_NEW)); |
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inode->i_size = 0; |
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inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO; |
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if (root) { |
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inode->i_op = &afs_dynroot_inode_operations; |
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inode->i_fop = &simple_dir_operations; |
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} else { |
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inode->i_op = &afs_autocell_inode_operations; |
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} |
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set_nlink(inode, 2); |
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inode->i_uid = GLOBAL_ROOT_UID; |
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inode->i_gid = GLOBAL_ROOT_GID; |
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inode->i_ctime = inode->i_atime = inode->i_mtime = current_time(inode); |
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inode->i_blocks = 0; |
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inode->i_generation = 0; |
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set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags); |
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if (!root) { |
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set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags); |
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inode->i_flags |= S_AUTOMOUNT; |
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} |
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inode->i_flags |= S_NOATIME; |
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unlock_new_inode(inode); |
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_leave(" = %p", inode); |
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return inode; |
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} |
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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_find_cell(net, name, len, afs_cell_trace_use_probe); |
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if (!IS_ERR(cell)) { |
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afs_unuse_cell(net, cell, afs_cell_trace_unuse_probe); |
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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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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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down_read(&net->cells_lock); |
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cell = 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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up_read(&net->cells_lock); |
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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 (flags & LOOKUP_CREATE) |
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return ERR_PTR(-EOPNOTSUPP); |
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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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if (root) { |
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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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}
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