afs: Support the AFS dynamic root
Support the AFS dynamic root which is a pseudo-volume that doesn't connect
to any server resource, but rather is just a root directory that
dynamically creates mountpoint directories where the name of such a
directory is the name of the cell.
Such a mount can be created thus:
mount -t afs none /afs -o dyn
Dynamic root superblocks aren't shared except by bind mounts and
propagation. Cell root volumes can then be mounted by referring to them by
name, e.g.:
ls /afs/grand.central.org/
ls /afs/.grand.central.org/
The kernel will upcall to consult the DNS if the address wasn't supplied
directly.
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 23c7f39..ba2b458 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -17,10 +17,13 @@
#include <linux/pagemap.h>
#include <linux/ctype.h>
#include <linux/sched.h>
+#include <linux/dns_resolver.h>
#include "internal.h"
static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags);
+static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentry,
+ unsigned int flags);
static int afs_dir_open(struct inode *inode, struct file *file);
static int afs_readdir(struct file *file, struct dir_context *ctx);
static int afs_d_revalidate(struct dentry *dentry, unsigned int flags);
@@ -64,6 +67,17 @@ const struct inode_operations afs_dir_inode_operations = {
.listxattr = afs_listxattr,
};
+const struct file_operations afs_dynroot_file_operations = {
+ .open = dcache_dir_open,
+ .release = dcache_dir_close,
+ .iterate_shared = dcache_readdir,
+ .llseek = dcache_dir_lseek,
+};
+
+const struct inode_operations afs_dynroot_inode_operations = {
+ .lookup = afs_dynroot_lookup,
+};
+
const struct dentry_operations afs_fs_dentry_operations = {
.d_revalidate = afs_d_revalidate,
.d_delete = afs_d_delete,
@@ -468,25 +482,58 @@ static int afs_do_lookup(struct inode *dir, struct dentry *dentry,
}
/*
+ * 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.
*/
-static struct inode *afs_try_auto_mntpt(
- int ret, struct dentry *dentry, struct inode *dir, struct key *key,
- struct afs_fid *fid)
+static struct inode *afs_try_auto_mntpt(struct dentry *dentry,
+ struct inode *dir, struct afs_fid *fid)
{
- const char *devname = dentry->d_name.name;
struct afs_vnode *vnode = AFS_FS_I(dir);
struct inode *inode;
+ int ret = -ENOENT;
- _enter("%d, %p{%pd}, {%x:%u}, %p",
- ret, dentry, dentry, vnode->fid.vid, vnode->fid.vnode, key);
+ _enter("%p{%pd}, {%x:%u}",
+ dentry, dentry, vnode->fid.vid, vnode->fid.vnode);
- if (ret != -ENOENT ||
- !test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
+ if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
goto out;
- inode = afs_iget_autocell(dir, devname, strlen(devname), key);
+ 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;
@@ -545,13 +592,16 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
ret = afs_do_lookup(dir, dentry, &fid, key);
if (ret < 0) {
- inode = afs_try_auto_mntpt(ret, dentry, dir, key, &fid);
- if (!IS_ERR(inode)) {
- key_put(key);
- goto success;
+ if (ret == -ENOENT) {
+ inode = afs_try_auto_mntpt(dentry, dir, &fid);
+ if (!IS_ERR(inode)) {
+ key_put(key);
+ goto success;
+ }
+
+ ret = PTR_ERR(inode);
}
- ret = PTR_ERR(inode);
key_put(key);
if (ret == -ENOENT) {
d_add(dentry, NULL);
@@ -583,12 +633,53 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
}
/*
+ * 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 afs_fid fid;
+ 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);
+ }
+
+ inode = afs_try_auto_mntpt(dentry, dir, &fid);
+ 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;
+}
+
+/*
* check that a dentry lookup hit has found a valid entry
* - NOTE! the hit can be a negative hit too, so we can't assume we have an
* inode
*/
static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
{
+ struct afs_super_info *as = dentry->d_sb->s_fs_info;
struct afs_vnode *vnode, *dir;
struct afs_fid uninitialized_var(fid);
struct dentry *parent;
@@ -600,6 +691,9 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
if (flags & LOOKUP_RCU)
return -ECHILD;
+ if (as->dyn_root)
+ return 1;
+
if (d_really_is_positive(dentry)) {
vnode = AFS_FS_I(d_inode(dentry));
_enter("{v={%x:%u} n=%pd fl=%lx},",