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Commit 4d673da1 authored by David Howells's avatar David Howells
Browse files

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: default avatarDavid Howells <dhowells@redhat.com>
parent 16280a15

Documentation/filesystems/afs.txt

+17 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ Contents: 
 - Overview.

 - Usage.

 - Mountpoints.

 - Dynamic root.

 - Proc filesystem.

 - The cell database.

 - Security.
@@ -127,6 +128,22 @@ mounted on /afs in one go by doing: 
	umount /afs





============

DYNAMIC ROOT

============



A mount option is available to create a serverless mount that is only usable

for dynamic lookup.  Creating such a mount can be done by, for example:



	mount -t afs none /afs -o dyn



This creates a mount that just has an empty directory at the root.  Attempting

to look up a name in this directory will cause a mountpoint to be created that

looks up a cell of the same name, for example:



	ls /afs/grand.central.org/





===============

PROC FILESYSTEM

===============

fs/afs/dir.c

+108 −14
Original line number Diff line number Diff line
@@ -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,
@@ -467,26 +481,59 @@ static int afs_do_lookup(struct inode *dir, struct dentry *dentry, 
	return 0;

}



/*

 * 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("%p{%pd}, {%x:%u}",

	       dentry, dentry, vnode->fid.vid, vnode->fid.vnode);



	_enter("%d, %p{%pd}, {%x:%u}, %p",

	       ret, dentry, dentry, vnode->fid.vid, vnode->fid.vnode, key);

	if (!test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))

		goto out;



	if (ret != -ENOENT ||

	    !test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))

	ret = afs_probe_cell_name(dentry);

	if (ret < 0)

		goto out;



	inode = afs_iget_autocell(dir, devname, strlen(devname), key);

	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 (ret == -ENOENT) {

			inode = afs_try_auto_mntpt(dentry, dir, &fid);

			if (!IS_ERR(inode)) {

				key_put(key);

				goto success;

			}



			ret = PTR_ERR(inode);

		}



		key_put(key);

		if (ret == -ENOENT) {

			d_add(dentry, NULL);
@@ -582,6 +632,46 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry, 
	return NULL;

}



/*

 * 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
@@ -589,6 +679,7 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry, 
 */

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},",

fs/afs/inode.c

+30 −18
Original line number Diff line number Diff line
@@ -147,7 +147,7 @@ int afs_iget5_test(struct inode *inode, void *opaque) 
 *

 * These pseudo inodes don't match anything.

 */

static int afs_iget5_autocell_test(struct inode *inode, void *opaque)

static int afs_iget5_pseudo_dir_test(struct inode *inode, void *opaque)

{

	return 0;

}
@@ -169,31 +169,34 @@ static int afs_iget5_set(struct inode *inode, void *opaque) 
}



/*

 * inode retrieval for autocell

 * Create an inode for a dynamic root directory or an autocell dynamic

 * automount dir.

 */

struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name,

				int namesz, struct key *key)

struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root)

{

	struct afs_iget_data data;

	struct afs_super_info *as;

	struct afs_vnode *vnode;

	struct super_block *sb;

	struct inode *inode;

	static atomic_t afs_autocell_ino;



	_enter("{%x:%u},%*.*s,",

	       AFS_FS_I(dir)->fid.vid, AFS_FS_I(dir)->fid.vnode,

	       namesz, namesz, dev_name ?: "");

	_enter("");



	sb = dir->i_sb;

	as = sb->s_fs_info;

	if (as->volume) {

		data.volume = as->volume;

		data.fid.vid = as->volume->vid;

	}

	if (root) {

		data.fid.vnode = 1;

		data.fid.unique = 1;

	} else {

		data.fid.vnode = atomic_inc_return(&afs_autocell_ino);

		data.fid.unique = 0;

	data.fid.vnode = 0;

	}



	inode = iget5_locked(sb, atomic_inc_return(&afs_autocell_ino),

			     afs_iget5_autocell_test, afs_iget5_set,

	inode = iget5_locked(sb, data.fid.vnode,

			     afs_iget5_pseudo_dir_test, afs_iget5_set,

			     &data);

	if (!inode) {

		_leave(" = -ENOMEM");
@@ -211,7 +214,12 @@ struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name, 


	inode->i_size		= 0;

	inode->i_mode		= S_IFDIR | S_IRUGO | S_IXUGO;

	if (root) {

		inode->i_op	= &afs_dynroot_inode_operations;

		inode->i_fop	= &afs_dynroot_file_operations;

	} else {

		inode->i_op	= &afs_autocell_inode_operations;

	}

	set_nlink(inode, 2);

	inode->i_uid		= GLOBAL_ROOT_UID;

	inode->i_gid		= GLOBAL_ROOT_GID;
@@ -223,8 +231,12 @@ struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name, 
	inode->i_generation	= 0;



	set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags);

	if (!root) {

		set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);

	inode->i_flags |= S_AUTOMOUNT | S_NOATIME;

		inode->i_flags |= S_AUTOMOUNT;

	}



	inode->i_flags |= S_NOATIME;

	unlock_new_inode(inode);

	_leave(" = %p", inode);

	return inode;

fs/afs/internal.h

+8 −4
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ struct afs_mount_params { 
	bool			rwpath;		/* T if the parent should be considered R/W */

	bool			force;		/* T to force cell type */

	bool			autocell;	/* T if set auto mount operation */

	bool			dyn_root;	/* T if dynamic root */

	afs_voltype_t		type;		/* type of volume requested */

	int			volnamesz;	/* size of volume name */

	const char		*volname;	/* name of volume to mount */
@@ -186,6 +187,7 @@ struct afs_super_info { 
	struct afs_net		*net;		/* Network namespace */

	struct afs_cell		*cell;		/* The cell in which the volume resides */

	struct afs_volume	*volume;	/* volume record */

	bool			dyn_root;	/* True if dynamic root */

};



static inline struct afs_super_info *AFS_FS_S(struct super_block *sb)
@@ -634,10 +636,13 @@ extern bool afs_cm_incoming_call(struct afs_call *); 
/*

 * dir.c

 */

extern bool afs_dir_check_page(struct inode *, struct page *);

extern const struct file_operations afs_dir_file_operations;

extern const struct inode_operations afs_dir_inode_operations;

extern const struct file_operations afs_dynroot_file_operations;

extern const struct inode_operations afs_dynroot_inode_operations;

extern const struct dentry_operations afs_fs_dentry_operations;

extern const struct file_operations afs_dir_file_operations;



extern bool afs_dir_check_page(struct inode *, struct page *);



/*

 * file.c
@@ -695,8 +700,7 @@ extern int afs_fs_get_capabilities(struct afs_net *, struct afs_server *, 
 */

extern int afs_fetch_status(struct afs_vnode *, struct key *);

extern int afs_iget5_test(struct inode *, void *);

extern struct inode *afs_iget_autocell(struct inode *, const char *, int,

				       struct key *);

extern struct inode *afs_iget_pseudo_dir(struct super_block *, bool);

extern struct inode *afs_iget(struct super_block *, struct key *,

			      struct afs_fid *, struct afs_file_status *,

			      struct afs_callback *,

fs/afs/mntpt.c

+11 −9
Original line number Diff line number Diff line
@@ -72,7 +72,7 @@ static int afs_mntpt_open(struct inode *inode, struct file *file) 
 */

static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)

{

	struct afs_super_info *super;

	struct afs_super_info *as;

	struct vfsmount *mnt;

	struct afs_vnode *vnode;

	struct page *page;
@@ -104,13 +104,13 @@ static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt) 
			goto error_no_page;



		if (mntpt->d_name.name[0] == '.') {

			devname[0] = '#';

			memcpy(devname + 1, mntpt->d_name.name, size - 1);

			devname[0] = '%';

			memcpy(devname + 1, mntpt->d_name.name + 1, size - 1);

			memcpy(devname + size, afs_root_cell,

			       sizeof(afs_root_cell));

			rwpath = true;

		} else {

			devname[0] = '%';

			devname[0] = '#';

			memcpy(devname + 1, mntpt->d_name.name, size);

			memcpy(devname + size + 1, afs_root_cell,

			       sizeof(afs_root_cell));
@@ -142,11 +142,13 @@ static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt) 
	}



	/* work out what options we want */

	super = AFS_FS_S(mntpt->d_sb);

	as = AFS_FS_S(mntpt->d_sb);

	if (as->cell) {

		memcpy(options, "cell=", 5);

	strcpy(options + 5, super->volume->cell->name);

	if (super->volume->type == AFSVL_RWVOL || rwpath)

		strcpy(options + 5, as->cell->name);

		if ((as->volume && as->volume->type == AFSVL_RWVOL) || rwpath)

			strcat(options, ",rwpath");

	}



	/* try and do the mount */

	_debug("--- attempting mount %s -o %s ---", devname, options);