Commit 4b93dc9b authored by Tejun Heo's avatar Tejun Heo Committed by Greg Kroah-Hartman
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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: default avatarTejun Heo <tj@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent df394fb5

fs/kernfs/inode.c

+3 −2
Original line number Diff line number Diff line
@@ -37,9 +37,10 @@ static const struct inode_operations sysfs_inode_operations = { 
	.setxattr	= sysfs_setxattr,

};



int __init sysfs_inode_init(void)

void __init sysfs_inode_init(void)

{

	return bdi_init(&sysfs_backing_dev_info);

	if (bdi_init(&sysfs_backing_dev_info))

		panic("failed to init sysfs_backing_dev_info");

}



static struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)

fs/kernfs/kernfs-internal.h

+1 −1
Original line number Diff line number Diff line
@@ -144,7 +144,7 @@ int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, 
		  struct kstat *stat);

int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,

		   size_t size, int flags);

int sysfs_inode_init(void);

void sysfs_inode_init(void);



/*

 * dir.c

fs/namespace.c

+2 −0
Original line number Diff line number Diff line
@@ -2790,6 +2790,8 @@ void __init mnt_init(void) 
	for (u = 0; u < HASH_SIZE; u++)

		INIT_LIST_HEAD(&mountpoint_hashtable[u]);



	kernfs_init();



	err = sysfs_init();

	if (err)

		printk(KERN_WARNING "%s: sysfs_init error: %d\n",

fs/sysfs/mount.c

+72 −32
Original line number Diff line number Diff line
@@ -86,18 +86,24 @@ static int sysfs_set_super(struct super_block *sb, void *data) 
	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 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, 
			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) {
@@ -132,6 +166,20 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, 
}



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 @@ static void sysfs_kill_sb(struct super_block *sb) 
	 * 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 @@ static struct file_system_type sysfs_fs_type = { 
	.fs_flags	= FS_USERNS_MOUNT,

};



int __init sysfs_init(void)

void __init kernfs_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;

					      0, SLAB_PANIC, NULL);

	sysfs_inode_init();

}



	err = sysfs_inode_init();

	if (err)

		goto out_err;

int __init sysfs_init(void)

{

	int 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;



	return 0;



out_destroy_root:

	if (err) {

		kernfs_destroy_root(sysfs_root);

out_err:

	kmem_cache_destroy(sysfs_dir_cachep);

	sysfs_dir_cachep = NULL;

		return err;

	}



	return 0;

}

include/linux/kernfs.h

+28 −0
Original line number Diff line number Diff line
@@ -18,6 +18,8 @@ struct file; 
struct iattr;

struct seq_file;

struct vm_area_struct;

struct super_block;

struct file_system_type;



struct sysfs_dirent;
@@ -109,6 +111,13 @@ void kernfs_enable_ns(struct sysfs_dirent *sd); 
int kernfs_setattr(struct sysfs_dirent *sd, const struct iattr *iattr);

void kernfs_notify(struct sysfs_dirent *sd);



const void *kernfs_super_ns(struct super_block *sb);

struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,

			       struct kernfs_root *root, const void *ns);

void kernfs_kill_sb(struct super_block *sb);



void kernfs_init(void);



#else	/* CONFIG_SYSFS */



static inline struct sysfs_dirent *
@@ -160,6 +169,18 @@ static inline int kernfs_setattr(struct sysfs_dirent *sd, 


static inline void kernfs_notify(struct sysfs_dirent *sd) { }



static inline const void *kernfs_super_ns(struct super_block *sb)

{ return NULL; }



static inline struct dentry *

kernfs_mount_ns(struct file_system_type *fs_type, int flags,

		struct kernfs_root *root, const void *ns)

{ return ERR_PTR(-ENOSYS); }



static inline void kernfs_kill_sb(struct super_block *sb) { }



static inline void kernfs_init(void) { }



#endif	/* CONFIG_SYSFS */



static inline struct sysfs_dirent *
@@ -201,4 +222,11 @@ static inline int kernfs_remove_by_name(struct sysfs_dirent *parent, 
	return kernfs_remove_by_name_ns(parent, name, NULL);

}



static inline struct dentry *

kernfs_mount(struct file_system_type *fs_type, int flags,

	     struct kernfs_root *root)

{

	return kernfs_mount_ns(fs_type, flags, root, NULL);

}



#endif	/* __LINUX_KERNFS_H */

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