| /* |
| * fs/kernfs/mount.c - kernfs mount implementation |
| * |
| * Copyright (c) 2001-3 Patrick Mochel |
| * Copyright (c) 2007 SUSE Linux Products GmbH |
| * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org> |
| * |
| * This file is released under the GPLv2. |
| */ |
| |
| #include <linux/fs.h> |
| #include <linux/mount.h> |
| #include <linux/init.h> |
| #include <linux/magic.h> |
| #include <linux/slab.h> |
| #include <linux/pagemap.h> |
| #include <linux/namei.h> |
| |
| #include "kernfs-internal.h" |
| |
| struct kmem_cache *kernfs_node_cache; |
| |
| static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data) |
| { |
| struct kernfs_root *root = kernfs_info(sb)->root; |
| struct kernfs_syscall_ops *scops = root->syscall_ops; |
| |
| if (scops && scops->remount_fs) |
| return scops->remount_fs(root, flags, data); |
| return 0; |
| } |
| |
| static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry) |
| { |
| struct kernfs_root *root = kernfs_root(dentry->d_fsdata); |
| struct kernfs_syscall_ops *scops = root->syscall_ops; |
| |
| if (scops && scops->show_options) |
| return scops->show_options(sf, root); |
| return 0; |
| } |
| |
| const struct super_operations kernfs_sops = { |
| .statfs = simple_statfs, |
| .drop_inode = generic_delete_inode, |
| .evict_inode = kernfs_evict_inode, |
| |
| .remount_fs = kernfs_sop_remount_fs, |
| .show_options = kernfs_sop_show_options, |
| }; |
| |
| /** |
| * kernfs_root_from_sb - determine kernfs_root associated with a super_block |
| * @sb: the super_block in question |
| * |
| * Return the kernfs_root associated with @sb. If @sb is not a kernfs one, |
| * %NULL is returned. |
| */ |
| struct kernfs_root *kernfs_root_from_sb(struct super_block *sb) |
| { |
| if (sb->s_op == &kernfs_sops) |
| return kernfs_info(sb)->root; |
| return NULL; |
| } |
| |
| /* |
| * find the next ancestor in the path down to @child, where @parent was the |
| * ancestor whose descendant we want to find. |
| * |
| * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root |
| * node. If @parent is b, then we return the node for c. |
| * Passing in d as @parent is not ok. |
| */ |
| static struct kernfs_node *find_next_ancestor(struct kernfs_node *child, |
| struct kernfs_node *parent) |
| { |
| if (child == parent) { |
| pr_crit_once("BUG in find_next_ancestor: called with parent == child"); |
| return NULL; |
| } |
| |
| while (child->parent != parent) { |
| if (!child->parent) |
| return NULL; |
| child = child->parent; |
| } |
| |
| return child; |
| } |
| |
| /** |
| * kernfs_node_dentry - get a dentry for the given kernfs_node |
| * @kn: kernfs_node for which a dentry is needed |
| * @sb: the kernfs super_block |
| */ |
| struct dentry *kernfs_node_dentry(struct kernfs_node *kn, |
| struct super_block *sb) |
| { |
| struct dentry *dentry; |
| struct kernfs_node *knparent = NULL; |
| |
| BUG_ON(sb->s_op != &kernfs_sops); |
| |
| dentry = dget(sb->s_root); |
| |
| /* Check if this is the root kernfs_node */ |
| if (!kn->parent) |
| return dentry; |
| |
| knparent = find_next_ancestor(kn, NULL); |
| if (WARN_ON(!knparent)) |
| return ERR_PTR(-EINVAL); |
| |
| do { |
| struct dentry *dtmp; |
| struct kernfs_node *kntmp; |
| |
| if (kn == knparent) |
| return dentry; |
| kntmp = find_next_ancestor(kn, knparent); |
| if (WARN_ON(!kntmp)) |
| return ERR_PTR(-EINVAL); |
| mutex_lock(&d_inode(dentry)->i_mutex); |
| dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name)); |
| mutex_unlock(&d_inode(dentry)->i_mutex); |
| dput(dentry); |
| if (IS_ERR(dtmp)) |
| return dtmp; |
| knparent = kntmp; |
| dentry = dtmp; |
| } while (true); |
| } |
| |
| static int kernfs_fill_super(struct super_block *sb, unsigned long magic) |
| { |
| struct kernfs_super_info *info = kernfs_info(sb); |
| struct inode *inode; |
| struct dentry *root; |
| |
| info->sb = sb; |
| sb->s_blocksize = PAGE_CACHE_SIZE; |
| sb->s_blocksize_bits = PAGE_CACHE_SHIFT; |
| sb->s_magic = magic; |
| sb->s_op = &kernfs_sops; |
| sb->s_time_gran = 1; |
| |
| /* get root inode, initialize and unlock it */ |
| mutex_lock(&kernfs_mutex); |
| inode = kernfs_get_inode(sb, info->root->kn); |
| mutex_unlock(&kernfs_mutex); |
| if (!inode) { |
| pr_debug("kernfs: could not get root inode\n"); |
| return -ENOMEM; |
| } |
| |
| /* instantiate and link root dentry */ |
| root = d_make_root(inode); |
| if (!root) { |
| pr_debug("%s: could not get root dentry!\n", __func__); |
| return -ENOMEM; |
| } |
| kernfs_get(info->root->kn); |
| root->d_fsdata = info->root->kn; |
| sb->s_root = root; |
| sb->s_d_op = &kernfs_dops; |
| return 0; |
| } |
| |
| static int kernfs_test_super(struct super_block *sb, void *data) |
| { |
| struct kernfs_super_info *sb_info = kernfs_info(sb); |
| struct kernfs_super_info *info = data; |
| |
| return sb_info->root == info->root && sb_info->ns == info->ns; |
| } |
| |
| static int kernfs_set_super(struct super_block *sb, void *data) |
| { |
| int error; |
| error = set_anon_super(sb, data); |
| if (!error) |
| sb->s_fs_info = data; |
| return error; |
| } |
| |
| /** |
| * kernfs_super_ns - determine the namespace tag of a kernfs super_block |
| * @sb: super_block of interest |
| * |
| * Return the namespace tag associated with kernfs super_block @sb. |
| */ |
| const void *kernfs_super_ns(struct super_block *sb) |
| { |
| struct kernfs_super_info *info = kernfs_info(sb); |
| |
| return info->ns; |
| } |
| |
| /** |
| * kernfs_mount_ns - kernfs mount helper |
| * @fs_type: file_system_type of the fs being mounted |
| * @flags: mount flags specified for the mount |
| * @root: kernfs_root of the hierarchy being mounted |
| * @magic: file system specific magic number |
| * @new_sb_created: tell the caller if we allocated a new superblock |
| * @ns: optional namespace tag of the mount |
| * |
| * This is to be called from each kernfs user's file_system_type->mount() |
| * implementation, which should pass through the specified @fs_type and |
| * @flags, and specify the hierarchy and namespace tag to mount via @root |
| * and @ns, respectively. |
| * |
| * The return value can be passed to the vfs layer verbatim. |
| */ |
| struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, |
| struct kernfs_root *root, unsigned long magic, |
| bool *new_sb_created, const void *ns) |
| { |
| struct super_block *sb; |
| struct kernfs_super_info *info; |
| int error; |
| |
| info = kzalloc(sizeof(*info), GFP_KERNEL); |
| if (!info) |
| return ERR_PTR(-ENOMEM); |
| |
| info->root = root; |
| info->ns = ns; |
| |
| sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info); |
| if (IS_ERR(sb) || sb->s_fs_info != info) |
| kfree(info); |
| if (IS_ERR(sb)) |
| return ERR_CAST(sb); |
| |
| if (new_sb_created) |
| *new_sb_created = !sb->s_root; |
| |
| if (!sb->s_root) { |
| struct kernfs_super_info *info = kernfs_info(sb); |
| |
| error = kernfs_fill_super(sb, magic); |
| if (error) { |
| deactivate_locked_super(sb); |
| return ERR_PTR(error); |
| } |
| sb->s_flags |= MS_ACTIVE; |
| |
| mutex_lock(&kernfs_mutex); |
| list_add(&info->node, &root->supers); |
| mutex_unlock(&kernfs_mutex); |
| } |
| |
| return dget(sb->s_root); |
| } |
| |
| /** |
| * kernfs_kill_sb - kill_sb for kernfs |
| * @sb: super_block being killed |
| * |
| * This can be used directly for file_system_type->kill_sb(). If a kernfs |
| * user needs extra cleanup, it can implement its own kill_sb() and call |
| * this function at the end. |
| */ |
| void kernfs_kill_sb(struct super_block *sb) |
| { |
| struct kernfs_super_info *info = kernfs_info(sb); |
| struct kernfs_node *root_kn = sb->s_root->d_fsdata; |
| |
| mutex_lock(&kernfs_mutex); |
| list_del(&info->node); |
| mutex_unlock(&kernfs_mutex); |
| |
| /* |
| * Remove the superblock from fs_supers/s_instances |
| * so we can't find it, before freeing kernfs_super_info. |
| */ |
| kill_anon_super(sb); |
| kfree(info); |
| kernfs_put(root_kn); |
| } |
| |
| /** |
| * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root |
| * @kernfs_root: the kernfs_root in question |
| * @ns: the namespace tag |
| * |
| * Pin the superblock so the superblock won't be destroyed in subsequent |
| * operations. This can be used to block ->kill_sb() which may be useful |
| * for kernfs users which dynamically manage superblocks. |
| * |
| * Returns NULL if there's no superblock associated to this kernfs_root, or |
| * -EINVAL if the superblock is being freed. |
| */ |
| struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns) |
| { |
| struct kernfs_super_info *info; |
| struct super_block *sb = NULL; |
| |
| mutex_lock(&kernfs_mutex); |
| list_for_each_entry(info, &root->supers, node) { |
| if (info->ns == ns) { |
| sb = info->sb; |
| if (!atomic_inc_not_zero(&info->sb->s_active)) |
| sb = ERR_PTR(-EINVAL); |
| break; |
| } |
| } |
| mutex_unlock(&kernfs_mutex); |
| return sb; |
| } |
| |
| void __init kernfs_init(void) |
| { |
| kernfs_node_cache = kmem_cache_create("kernfs_node_cache", |
| sizeof(struct kernfs_node), |
| 0, SLAB_PANIC, NULL); |
| } |