sysfs, kernfs: prepare mount path for kernfs
We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly. This patch
rearranges mount path so that the kernfs and sysfs parts are separate.
* As sysfs_super_info won't be visible outside kernfs proper,
kernfs_super_ns() is added to allow kernfs users to access a
super_block's namespace tag.
* Generic mount operation is separated out into kernfs_mount_ns().
sysfs_mount() now just performs sysfs-specific permission check,
acquires namespace tag, and invokes kernfs_mount_ns().
* Generic superblock release is separated out into kernfs_kill_sb()
which can be used directly as file_system_type->kill_sb(). As sysfs
needs to put the namespace tag, sysfs_kill_sb() wraps
kernfs_kill_sb() with ns tag put.
* sysfs_dir_cachep init and sysfs_inode_init() are separated out into
kernfs_init(). kernfs_init() uses only small amount of memory and
trying to handle and propagate kernfs_init() failure doesn't make
much sense. Use SLAB_PANIC for sysfs_dir_cachep and make
sysfs_inode_init() panic on failure.
After this change, kernfs_init() should be called before
sysfs_init(), fs/namespace.c::mnt_init() modified accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index f143b20..5384732 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -86,18 +86,24 @@
return error;
}
-static void free_sysfs_super_info(struct sysfs_super_info *info)
+/**
+ * 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)
{
- kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)info->ns);
- kfree(info);
+ struct sysfs_super_info *info = sysfs_info(sb);
+
+ return info->ns;
}
static struct dentry *sysfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
- struct sysfs_super_info *info;
- struct super_block *sb;
- int error;
+ struct dentry *root;
+ void *ns;
if (!(flags & MS_KERNMOUNT)) {
if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
@@ -107,16 +113,44 @@
return ERR_PTR(-EPERM);
}
+ ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+ root = kernfs_mount_ns(fs_type, flags, sysfs_root, ns);
+ if (IS_ERR(root))
+ kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
+ return root;
+}
+
+/**
+ * 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
+ * @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, const void *ns)
+{
+ struct super_block *sb;
+ struct sysfs_super_info *info;
+ int error;
+
info = kzalloc(sizeof(*info), GFP_KERNEL);
if (!info)
return ERR_PTR(-ENOMEM);
- info->root = sysfs_root;
- info->ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+ info->root = root;
+ info->ns = ns;
sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
if (IS_ERR(sb) || sb->s_fs_info != info)
- free_sysfs_super_info(info);
+ kfree(info);
if (IS_ERR(sb))
return ERR_CAST(sb);
if (!sb->s_root) {
@@ -133,6 +167,20 @@
static void sysfs_kill_sb(struct super_block *sb)
{
+ kernfs_kill_sb(sb);
+ kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)kernfs_super_ns(sb));
+}
+
+/**
+ * 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 sysfs_super_info *info = sysfs_info(sb);
struct sysfs_dirent *root_sd = sb->s_root->d_fsdata;
@@ -141,7 +189,7 @@
* so we can't find it, before freeing sysfs_super_info.
*/
kill_anon_super(sb);
- free_sysfs_super_info(info);
+ kfree(info);
kernfs_put(root_sd);
}
@@ -152,37 +200,29 @@
.fs_flags = FS_USERNS_MOUNT,
};
+void __init kernfs_init(void)
+{
+ sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
+ sizeof(struct sysfs_dirent),
+ 0, SLAB_PANIC, NULL);
+ sysfs_inode_init();
+}
+
int __init sysfs_init(void)
{
int err;
- sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache",
- sizeof(struct sysfs_dirent),
- 0, 0, NULL);
- if (!sysfs_dir_cachep)
- return -ENOMEM;
-
- err = sysfs_inode_init();
- if (err)
- goto out_err;
-
sysfs_root = kernfs_create_root(NULL);
- if (IS_ERR(sysfs_root)) {
- err = PTR_ERR(sysfs_root);
- goto out_err;
- }
+ if (IS_ERR(sysfs_root))
+ return PTR_ERR(sysfs_root);
+
sysfs_root_sd = sysfs_root->sd;
err = register_filesystem(&sysfs_fs_type);
- if (err)
- goto out_destroy_root;
+ if (err) {
+ kernfs_destroy_root(sysfs_root);
+ return err;
+ }
return 0;
-
-out_destroy_root:
- kernfs_destroy_root(sysfs_root);
-out_err:
- kmem_cache_destroy(sysfs_dir_cachep);
- sysfs_dir_cachep = NULL;
- return err;
}