1 /* 2 * fs/kernfs/mount.c - kernfs mount implementation 3 * 4 * Copyright (c) 2001-3 Patrick Mochel 5 * Copyright (c) 2007 SUSE Linux Products GmbH 6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org> 7 * 8 * This file is released under the GPLv2. 9 */ 10 11 #include <linux/fs.h> 12 #include <linux/mount.h> 13 #include <linux/init.h> 14 #include <linux/magic.h> 15 #include <linux/slab.h> 16 #include <linux/pagemap.h> 17 18 #include "kernfs-internal.h" 19 20 struct kmem_cache *kernfs_node_cache; 21 22 static const struct super_operations kernfs_sops = { 23 .statfs = simple_statfs, 24 .drop_inode = generic_delete_inode, 25 .evict_inode = kernfs_evict_inode, 26 }; 27 28 static int kernfs_fill_super(struct super_block *sb) 29 { 30 struct kernfs_super_info *info = kernfs_info(sb); 31 struct inode *inode; 32 struct dentry *root; 33 34 sb->s_blocksize = PAGE_CACHE_SIZE; 35 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 36 sb->s_magic = SYSFS_MAGIC; 37 sb->s_op = &kernfs_sops; 38 sb->s_time_gran = 1; 39 40 /* get root inode, initialize and unlock it */ 41 mutex_lock(&kernfs_mutex); 42 inode = kernfs_get_inode(sb, info->root->kn); 43 mutex_unlock(&kernfs_mutex); 44 if (!inode) { 45 pr_debug("kernfs: could not get root inode\n"); 46 return -ENOMEM; 47 } 48 49 /* instantiate and link root dentry */ 50 root = d_make_root(inode); 51 if (!root) { 52 pr_debug("%s: could not get root dentry!\n", __func__); 53 return -ENOMEM; 54 } 55 kernfs_get(info->root->kn); 56 root->d_fsdata = info->root->kn; 57 sb->s_root = root; 58 sb->s_d_op = &kernfs_dops; 59 return 0; 60 } 61 62 static int kernfs_test_super(struct super_block *sb, void *data) 63 { 64 struct kernfs_super_info *sb_info = kernfs_info(sb); 65 struct kernfs_super_info *info = data; 66 67 return sb_info->root == info->root && sb_info->ns == info->ns; 68 } 69 70 static int kernfs_set_super(struct super_block *sb, void *data) 71 { 72 int error; 73 error = set_anon_super(sb, data); 74 if (!error) 75 sb->s_fs_info = data; 76 return error; 77 } 78 79 /** 80 * kernfs_super_ns - determine the namespace tag of a kernfs super_block 81 * @sb: super_block of interest 82 * 83 * Return the namespace tag associated with kernfs super_block @sb. 84 */ 85 const void *kernfs_super_ns(struct super_block *sb) 86 { 87 struct kernfs_super_info *info = kernfs_info(sb); 88 89 return info->ns; 90 } 91 92 /** 93 * kernfs_mount_ns - kernfs mount helper 94 * @fs_type: file_system_type of the fs being mounted 95 * @flags: mount flags specified for the mount 96 * @root: kernfs_root of the hierarchy being mounted 97 * @new_sb_created: tell the caller if we allocated a new superblock 98 * @ns: optional namespace tag of the mount 99 * 100 * This is to be called from each kernfs user's file_system_type->mount() 101 * implementation, which should pass through the specified @fs_type and 102 * @flags, and specify the hierarchy and namespace tag to mount via @root 103 * and @ns, respectively. 104 * 105 * The return value can be passed to the vfs layer verbatim. 106 */ 107 struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, 108 struct kernfs_root *root, bool *new_sb_created, 109 const void *ns) 110 { 111 struct super_block *sb; 112 struct kernfs_super_info *info; 113 int error; 114 115 info = kzalloc(sizeof(*info), GFP_KERNEL); 116 if (!info) 117 return ERR_PTR(-ENOMEM); 118 119 info->root = root; 120 info->ns = ns; 121 122 sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info); 123 if (IS_ERR(sb) || sb->s_fs_info != info) 124 kfree(info); 125 if (IS_ERR(sb)) 126 return ERR_CAST(sb); 127 128 if (new_sb_created) 129 *new_sb_created = !sb->s_root; 130 131 if (!sb->s_root) { 132 error = kernfs_fill_super(sb); 133 if (error) { 134 deactivate_locked_super(sb); 135 return ERR_PTR(error); 136 } 137 sb->s_flags |= MS_ACTIVE; 138 } 139 140 return dget(sb->s_root); 141 } 142 143 /** 144 * kernfs_kill_sb - kill_sb for kernfs 145 * @sb: super_block being killed 146 * 147 * This can be used directly for file_system_type->kill_sb(). If a kernfs 148 * user needs extra cleanup, it can implement its own kill_sb() and call 149 * this function at the end. 150 */ 151 void kernfs_kill_sb(struct super_block *sb) 152 { 153 struct kernfs_super_info *info = kernfs_info(sb); 154 struct kernfs_node *root_kn = sb->s_root->d_fsdata; 155 156 /* 157 * Remove the superblock from fs_supers/s_instances 158 * so we can't find it, before freeing kernfs_super_info. 159 */ 160 kill_anon_super(sb); 161 kfree(info); 162 kernfs_put(root_kn); 163 } 164 165 void __init kernfs_init(void) 166 { 167 kernfs_node_cache = kmem_cache_create("kernfs_node_cache", 168 sizeof(struct kernfs_node), 169 0, SLAB_PANIC, NULL); 170 kernfs_inode_init(); 171 } 172