diff options
Diffstat (limited to 'fs/afs/dynroot.c')
| -rw-r--r-- | fs/afs/dynroot.c | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c new file mode 100644 index 000000000000..983f3946ab57 --- /dev/null +++ b/fs/afs/dynroot.c @@ -0,0 +1,209 @@ +/* dir.c: 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, "ipv4", 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 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) +{ + struct afs_vnode *vnode; + struct inode *inode; + int ret; + + vnode = AFS_FS_I(dir); + + _enter("%pd", dentry); + + ASSERTCMP(d_inode(dentry), ==, NULL); + + 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); + + inode = afs_try_auto_mntpt(dentry, dir); + if (IS_ERR(inode)) { + ret = PTR_ERR(inode); + if (ret == -ENOENT) { + d_add(dentry, NULL); + _leave(" = NULL [negative]"); + return NULL; + } + _leave(" = %d [do]", ret); + return ERR_PTR(ret); + } + + d_add(dentry, inode); + _leave(" = 0 { ino=%lu v=%u }", + d_inode(dentry)->i_ino, d_inode(dentry)->i_generation); + return NULL; +} + +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, +}; |