Commit 37ab6368 authored by David Howells's avatar David Howells
Browse files

afs: Implement @cell substitution handling 



Implement @cell substitution handling such that if @cell is seen as a name
in a dynamic root mount, then the name of the root cell for that network
namespace will be substituted for @cell during lookup.

The substitution of @cell for the current net namespace is set by writing
the cell name to /proc/fs/afs/rootcell.  The value can be obtained by
reading the file.

For example:

	# mount -t afs none /kafs -o dyn
	# echo grand.central.org >/proc/fs/afs/rootcell
	# ls /kafs/@cell
	archive/  cvs/  doc/  local/  project/  service/  software/  user/  www/
	# cat /proc/fs/afs/rootcell
	grand.central.org

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent 6f8880d8

fs/afs/cell.c

+2 −0
Original line number Diff line number Diff line
@@ -130,6 +130,8 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net, 
		_leave(" = -ENAMETOOLONG");

		return ERR_PTR(-ENAMETOOLONG);

	}

	if (namelen == 5 && memcmp(name, "@cell", 5) == 0)

		return ERR_PTR(-EINVAL);



	_enter("%*.*s,%s", namelen, namelen, name, vllist);

fs/afs/dir.c

+53 −0
Original line number Diff line number Diff line
@@ -908,6 +908,55 @@ success: 
	return NULL;

}



/*

 * 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.

 */
@@ -929,6 +978,10 @@ static struct dentry *afs_dynroot_lookup(struct inode *dir, struct dentry *dentr 
		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);

fs/afs/proc.c

+34 −1
Original line number Diff line number Diff line
@@ -334,7 +334,40 @@ inval: 
static ssize_t afs_proc_rootcell_read(struct file *file, char __user *buf,

				      size_t size, loff_t *_pos)

{

	struct afs_cell *cell;

	struct afs_net *net = afs_proc2net(file);

	unsigned int seq = 0;

	char name[AFS_MAXCELLNAME + 1];

	int len;



	if (*_pos > 0)

		return 0;

	if (!net->ws_cell)

		return 0;



	rcu_read_lock();

	do {

		read_seqbegin_or_lock(&net->cells_lock, &seq);

		len = 0;

		cell = rcu_dereference_raw(net->ws_cell);

		if (cell) {

			len = cell->name_len;

			memcpy(name, cell->name, len);

		}

	} while (need_seqretry(&net->cells_lock, seq));

	done_seqretry(&net->cells_lock, seq);

	rcu_read_unlock();



	if (!len)

		return 0;



	name[len++] = '\n';

	if (len > size)

		len = size;

	if (copy_to_user(buf, name, len) != 0)

		return -EFAULT;

	*_pos = 1;

	return len;

}



/*

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