/* * 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 "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; } 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); }