From 37ab636880cbc95ba87a5790bee23a1c813089c6 Mon Sep 17 00:00:00 2001 From: David Howells <dhowells@redhat.com> Date: Fri, 6 Apr 2018 14:17:23 +0100 Subject: 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: David Howells <dhowells@redhat.com> --- fs/afs/dir.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) (limited to 'fs/afs/dir.c') diff --git a/fs/afs/dir.c b/fs/afs/dir.c index 3ebd741b74d0..b073976db8d2 100644 --- a/fs/afs/dir.c +++ b/fs/afs/dir.c @@ -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); -- cgit v1.2.3