X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Fsuper.c;h=1943fdf655faca2d3d1810cca8b36ac80c9d3593;hb=6e8341a11eb21826b7192d0bb88cb5b44900a9af;hp=15671cd048b146b8315fb11012cddfd796ce82c4;hpb=cf9a2ae8d49948f861b56e5333530e491a9da190;p=safe%2Fjmp%2Flinux-2.6

diff --git a/fs/super.c b/fs/super.c
index 15671cd..1943fdf 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -15,7 +15,7 @@
  *  Added kerneld support: Jacques Gelinas and Bjorn Ekwall
  *  Added change_root: Werner Almesberger & Hans Lermen, Feb '96
  *  Added options to /proc/mounts:
- *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
+ *    Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
  *  Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
  *  Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
  */
@@ -37,13 +37,12 @@
 #include <linux/idr.h>
 #include <linux/kobject.h>
 #include <linux/mutex.h>
+#include <linux/file.h>
+#include <linux/async.h>
 #include <asm/uaccess.h>
+#include "internal.h"
 
 
-void get_filesystem(struct file_system_type *fs);
-void put_filesystem(struct file_system_type *fs);
-struct file_system_type *get_fs_type(const char *name);
-
 LIST_HEAD(super_blocks);
 DEFINE_SPINLOCK(sb_lock);
 
@@ -67,10 +66,13 @@ static struct super_block *alloc_super(struct file_system_type *type)
 		}
 		INIT_LIST_HEAD(&s->s_dirty);
 		INIT_LIST_HEAD(&s->s_io);
+		INIT_LIST_HEAD(&s->s_more_io);
 		INIT_LIST_HEAD(&s->s_files);
 		INIT_LIST_HEAD(&s->s_instances);
 		INIT_HLIST_HEAD(&s->s_anon);
 		INIT_LIST_HEAD(&s->s_inodes);
+		INIT_LIST_HEAD(&s->s_dentry_lru);
+		INIT_LIST_HEAD(&s->s_async_list);
 		init_rwsem(&s->s_umount);
 		mutex_init(&s->s_lock);
 		lockdep_set_class(&s->s_umount, &type->s_umount_key);
@@ -80,7 +82,22 @@ static struct super_block *alloc_super(struct file_system_type *type)
 		 * lock ordering than usbfs:
 		 */
 		lockdep_set_class(&s->s_lock, &type->s_lock_key);
-		down_write(&s->s_umount);
+		/*
+		 * sget() can have s_umount recursion.
+		 *
+		 * When it cannot find a suitable sb, it allocates a new
+		 * one (this one), and tries again to find a suitable old
+		 * one.
+		 *
+		 * In case that succeeds, it will acquire the s_umount
+		 * lock of the old one. Since these are clearly distrinct
+		 * locks, and this object isn't exposed yet, there's no
+		 * risk of deadlocks.
+		 *
+		 * Annotate this by putting this lock in a different
+		 * subclass.
+		 */
+		down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
 		s->s_count = S_BIAS;
 		atomic_set(&s->s_active, 1);
 		mutex_init(&s->s_vfs_rename_mutex);
@@ -107,6 +124,8 @@ out:
 static inline void destroy_super(struct super_block *s)
 {
 	security_sb_free(s);
+	kfree(s->s_subtype);
+	kfree(s->s_options);
 	kfree(s);
 }
 
@@ -116,7 +135,7 @@ static inline void destroy_super(struct super_block *s)
  * Drop a superblock's refcount.  Returns non-zero if the superblock was
  * destroyed.  The caller must hold sb_lock.
  */
-int __put_super(struct super_block *sb)
+static int __put_super(struct super_block *sb)
 {
 	int ret = 0;
 
@@ -178,7 +197,7 @@ void deactivate_super(struct super_block *s)
 	if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
 		s->s_count -= S_BIAS-1;
 		spin_unlock(&sb_lock);
-		DQUOT_OFF(s);
+		vfs_dq_off(s, 0);
 		down_write(&s->s_umount);
 		fs->kill_sb(s);
 		put_filesystem(fs);
@@ -189,6 +208,34 @@ void deactivate_super(struct super_block *s)
 EXPORT_SYMBOL(deactivate_super);
 
 /**
+ *	deactivate_locked_super	-	drop an active reference to superblock
+ *	@s: superblock to deactivate
+ *
+ *	Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that
+ *	it does not unlock it until it's all over.  As the result, it's safe to
+ *	use to dispose of new superblock on ->get_sb() failure exits - nobody
+ *	will see the sucker until it's all over.  Equivalent using up_write +
+ *	deactivate_super is safe for that purpose only if superblock is either
+ *	safe to use or has NULL ->s_root when we unlock.
+ */
+void deactivate_locked_super(struct super_block *s)
+{
+	struct file_system_type *fs = s->s_type;
+	if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
+		s->s_count -= S_BIAS-1;
+		spin_unlock(&sb_lock);
+		vfs_dq_off(s, 0);
+		fs->kill_sb(s);
+		put_filesystem(fs);
+		put_super(s);
+	} else {
+		up_write(&s->s_umount);
+	}
+}
+
+EXPORT_SYMBOL(deactivate_locked_super);
+
+/**
  *	grab_super - acquire an active reference
  *	@s: reference we are trying to make active
  *
@@ -221,6 +268,24 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
 }
 
 /*
+ * Superblock locking.  We really ought to get rid of these two.
+ */
+void lock_super(struct super_block * sb)
+{
+	get_fs_excl();
+	mutex_lock(&sb->s_lock);
+}
+
+void unlock_super(struct super_block * sb)
+{
+	put_fs_excl();
+	mutex_unlock(&sb->s_lock);
+}
+
+EXPORT_SYMBOL(lock_super);
+EXPORT_SYMBOL(unlock_super);
+
+/*
  * Write out and wait upon all dirty data associated with this
  * superblock.  Filesystem data as well as the underlying block
  * device.  Takes the superblock lock.  Requires a second blkdev
@@ -229,7 +294,7 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
 void __fsync_super(struct super_block *sb)
 {
 	sync_inodes_sb(sb, 0);
-	DQUOT_SYNC(sb);
+	vfs_dq_sync(sb);
 	lock_super(sb);
 	if (sb->s_dirt && sb->s_op->write_super)
 		sb->s_op->write_super(sb);
@@ -250,6 +315,7 @@ int fsync_super(struct super_block *sb)
 	__fsync_super(sb);
 	return sync_blockdev(sb->s_bdev);
 }
+EXPORT_SYMBOL_GPL(fsync_super);
 
 /**
  *	generic_shutdown_super	-	common helper for ->kill_sb()
@@ -260,20 +326,27 @@ int fsync_super(struct super_block *sb)
  *	that need destruction out of superblock, call generic_shutdown_super()
  *	and release aforementioned objects.  Note: dentries and inodes _are_
  *	taken care of and do not need specific handling.
+ *
+ *	Upon calling this function, the filesystem may no longer alter or
+ *	rearrange the set of dentries belonging to this super_block, nor may it
+ *	change the attachments of dentries to inodes.
  */
 void generic_shutdown_super(struct super_block *sb)
 {
-	struct dentry *root = sb->s_root;
-	struct super_operations *sop = sb->s_op;
+	const struct super_operations *sop = sb->s_op;
+
 
-	if (root) {
-		sb->s_root = NULL;
-		shrink_dcache_parent(root);
-		shrink_dcache_sb(sb);
-		dput(root);
+	if (sb->s_root) {
+		shrink_dcache_for_umount(sb);
 		fsync_super(sb);
 		lock_super(sb);
 		sb->s_flags &= ~MS_ACTIVE;
+
+		/*
+		 * wait for asynchronous fs operations to finish before going further
+		 */
+		async_synchronize_full_domain(&sb->s_async_list);
+
 		/* bad name - it should be evict_inodes() */
 		invalidate_inodes(sb);
 		lock_kernel();
@@ -316,21 +389,23 @@ struct super_block *sget(struct file_system_type *type,
 			void *data)
 {
 	struct super_block *s = NULL;
-	struct list_head *p;
+	struct super_block *old;
 	int err;
 
 retry:
 	spin_lock(&sb_lock);
-	if (test) list_for_each(p, &type->fs_supers) {
-		struct super_block *old;
-		old = list_entry(p, struct super_block, s_instances);
-		if (!test(old, data))
-			continue;
-		if (!grab_super(old))
-			goto retry;
-		if (s)
-			destroy_super(s);
-		return old;
+	if (test) {
+		list_for_each_entry(old, &type->fs_supers, s_instances) {
+			if (!test(old, data))
+				continue;
+			if (!grab_super(old))
+				goto retry;
+			if (s) {
+				up_write(&s->s_umount);
+				destroy_super(s);
+			}
+			return old;
+		}
 	}
 	if (!s) {
 		spin_unlock(&sb_lock);
@@ -343,6 +418,7 @@ retry:
 	err = set(s, data);
 	if (err) {
 		spin_unlock(&sb_lock);
+		up_write(&s->s_umount);
 		destroy_super(s);
 		return ERR_PTR(err);
 	}
@@ -401,7 +477,7 @@ restart:
 }
 
 /*
- * Call the ->sync_fs super_op against all filesytems which are r/w and
+ * Call the ->sync_fs super_op against all filesystems which are r/w and
  * which implement it.
  *
  * This operation is careful to avoid the livelock which could easily happen
@@ -409,7 +485,7 @@ restart:
  * is used only here.  We set it against all filesystems and then clear it as
  * we sync them.  So redirtied filesystems are skipped.
  *
- * But if process A is currently running sync_filesytems and then process B
+ * But if process A is currently running sync_filesystems and then process B
  * calls sync_filesystems as well, process B will set all the s_need_sync_fs
  * flags again, which will cause process A to resync everything.  Fix that with
  * a local mutex.
@@ -441,6 +517,7 @@ restart:
 		sb->s_count++;
 		spin_unlock(&sb_lock);
 		down_read(&sb->s_umount);
+		async_synchronize_full_domain(&sb->s_async_list);
 		if (sb->s_root && (wait || sb->s_dirt))
 			sb->s_op->sync_fs(sb, wait);
 		up_read(&sb->s_umount);
@@ -514,7 +591,7 @@ rescan:
 	return NULL;
 }
 
-asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
+SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
 {
         struct super_block *s;
         struct ustat tmp;
@@ -539,21 +616,40 @@ out:
 }
 
 /**
- *	mark_files_ro
+ *	mark_files_ro - mark all files read-only
  *	@sb: superblock in question
  *
- *	All files are marked read/only.  We don't care about pending
- *	delete files so this should be used in 'force' mode only
+ *	All files are marked read-only.  We don't care about pending
+ *	delete files so this should be used in 'force' mode only.
  */
 
 static void mark_files_ro(struct super_block *sb)
 {
 	struct file *f;
 
+retry:
 	file_list_lock();
 	list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
-		if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
-			f->f_mode &= ~FMODE_WRITE;
+		struct vfsmount *mnt;
+		if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
+		       continue;
+		if (!file_count(f))
+			continue;
+		if (!(f->f_mode & FMODE_WRITE))
+			continue;
+		f->f_mode &= ~FMODE_WRITE;
+		if (file_check_writeable(f) != 0)
+			continue;
+		file_release_write(f);
+		mnt = mntget(f->f_path.mnt);
+		file_list_unlock();
+		/*
+		 * This can sleep, so we can't hold
+		 * the file_list_lock() spinlock.
+		 */
+		mnt_drop_write(mnt);
+		mntput(mnt);
+		goto retry;
 	}
 	file_list_unlock();
 }
@@ -570,9 +666,12 @@ static void mark_files_ro(struct super_block *sb)
 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 {
 	int retval;
+	int remount_rw;
 	
+#ifdef CONFIG_BLOCK
 	if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
 		return -EACCES;
+#endif
 	if (flags & MS_RDONLY)
 		acct_auto_close(sb);
 	shrink_dcache_sb(sb);
@@ -585,7 +684,11 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 			mark_files_ro(sb);
 		else if (!fs_may_remount_ro(sb))
 			return -EBUSY;
+		retval = vfs_dq_off(sb, 1);
+		if (retval < 0 && retval != -ENOSYS)
+			return -EBUSY;
 	}
+	remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
 
 	if (sb->s_op->remount_fs) {
 		lock_super(sb);
@@ -595,10 +698,12 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 			return retval;
 	}
 	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
+	if (remount_rw)
+		vfs_dq_quota_on_remount(sb);
 	return 0;
 }
 
-static void do_emergency_remount(unsigned long foo)
+static void do_emergency_remount(struct work_struct *work)
 {
 	struct super_block *sb;
 
@@ -621,12 +726,19 @@ static void do_emergency_remount(unsigned long foo)
 		spin_lock(&sb_lock);
 	}
 	spin_unlock(&sb_lock);
+	kfree(work);
 	printk("Emergency Remount complete\n");
 }
 
 void emergency_remount(void)
 {
-	pdflush_operation(do_emergency_remount, 0);
+	struct work_struct *work;
+
+	work = kmalloc(sizeof(*work), GFP_ATOMIC);
+	if (work) {
+		INIT_WORK(work, do_emergency_remount);
+		schedule_work(work);
+	}
 }
 
 /*
@@ -634,7 +746,7 @@ void emergency_remount(void)
  * filesystems which don't use real block-devices.  -- jrs
  */
 
-static struct idr unnamed_dev_idr;
+static DEFINE_IDA(unnamed_dev_ida);
 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
 
 int set_anon_super(struct super_block *s, void *data)
@@ -643,10 +755,10 @@ int set_anon_super(struct super_block *s, void *data)
 	int error;
 
  retry:
-	if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
+	if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
 		return -ENOMEM;
 	spin_lock(&unnamed_dev_lock);
-	error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
+	error = ida_get_new(&unnamed_dev_ida, &dev);
 	spin_unlock(&unnamed_dev_lock);
 	if (error == -EAGAIN)
 		/* We raced and lost with another CPU. */
@@ -656,7 +768,7 @@ int set_anon_super(struct super_block *s, void *data)
 
 	if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
 		spin_lock(&unnamed_dev_lock);
-		idr_remove(&unnamed_dev_idr, dev);
+		ida_remove(&unnamed_dev_ida, dev);
 		spin_unlock(&unnamed_dev_lock);
 		return -EMFILE;
 	}
@@ -672,17 +784,12 @@ void kill_anon_super(struct super_block *sb)
 
 	generic_shutdown_super(sb);
 	spin_lock(&unnamed_dev_lock);
-	idr_remove(&unnamed_dev_idr, slot);
+	ida_remove(&unnamed_dev_ida, slot);
 	spin_unlock(&unnamed_dev_lock);
 }
 
 EXPORT_SYMBOL(kill_anon_super);
 
-void __init unnamed_dev_init(void)
-{
-	idr_init(&unnamed_dev_idr);
-}
-
 void kill_litter_super(struct super_block *sb)
 {
 	if (sb->s_root)
@@ -692,6 +799,46 @@ void kill_litter_super(struct super_block *sb)
 
 EXPORT_SYMBOL(kill_litter_super);
 
+static int ns_test_super(struct super_block *sb, void *data)
+{
+	return sb->s_fs_info == data;
+}
+
+static int ns_set_super(struct super_block *sb, void *data)
+{
+	sb->s_fs_info = data;
+	return set_anon_super(sb, NULL);
+}
+
+int get_sb_ns(struct file_system_type *fs_type, int flags, void *data,
+	int (*fill_super)(struct super_block *, void *, int),
+	struct vfsmount *mnt)
+{
+	struct super_block *sb;
+
+	sb = sget(fs_type, ns_test_super, ns_set_super, data);
+	if (IS_ERR(sb))
+		return PTR_ERR(sb);
+
+	if (!sb->s_root) {
+		int err;
+		sb->s_flags = flags;
+		err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
+		if (err) {
+			deactivate_locked_super(sb);
+			return err;
+		}
+
+		sb->s_flags |= MS_ACTIVE;
+	}
+
+	simple_set_mnt(mnt, sb);
+	return 0;
+}
+
+EXPORT_SYMBOL(get_sb_ns);
+
+#ifdef CONFIG_BLOCK
 static int set_bdev_super(struct super_block *s, void *data)
 {
 	s->s_bdev = data;
@@ -704,16 +851,6 @@ static int test_bdev_super(struct super_block *s, void *data)
 	return (void *)s->s_bdev == data;
 }
 
-static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
-{
-	if (bdev->bd_disk) {
-		if (bdev->bd_part)
-			kobject_uevent(&bdev->bd_part->kobj, action);
-		else
-			kobject_uevent(&bdev->bd_disk->kobj, action);
-	}
-}
-
 int get_sb_bdev(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data,
 	int (*fill_super)(struct super_block *, void *, int),
@@ -721,9 +858,13 @@ int get_sb_bdev(struct file_system_type *fs_type,
 {
 	struct block_device *bdev;
 	struct super_block *s;
+	fmode_t mode = FMODE_READ;
 	int error = 0;
 
-	bdev = open_bdev_excl(dev_name, flags, fs_type);
+	if (!(flags & MS_RDONLY))
+		mode |= FMODE_WRITE;
+
+	bdev = open_bdev_exclusive(dev_name, mode, fs_type);
 	if (IS_ERR(bdev))
 		return PTR_ERR(bdev);
 
@@ -732,44 +873,44 @@ int get_sb_bdev(struct file_system_type *fs_type,
 	 * will protect the lockfs code from trying to start a snapshot
 	 * while we are mounting
 	 */
-	mutex_lock(&bdev->bd_mount_mutex);
+	down(&bdev->bd_mount_sem);
 	s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
-	mutex_unlock(&bdev->bd_mount_mutex);
+	up(&bdev->bd_mount_sem);
 	if (IS_ERR(s))
 		goto error_s;
 
 	if (s->s_root) {
 		if ((flags ^ s->s_flags) & MS_RDONLY) {
-			up_write(&s->s_umount);
-			deactivate_super(s);
+			deactivate_locked_super(s);
 			error = -EBUSY;
 			goto error_bdev;
 		}
 
-		close_bdev_excl(bdev);
+		close_bdev_exclusive(bdev, mode);
 	} else {
 		char b[BDEVNAME_SIZE];
 
 		s->s_flags = flags;
+		s->s_mode = mode;
 		strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 		sb_set_blocksize(s, block_size(bdev));
 		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 		if (error) {
-			up_write(&s->s_umount);
-			deactivate_super(s);
+			deactivate_locked_super(s);
 			goto error;
 		}
 
 		s->s_flags |= MS_ACTIVE;
-		bdev_uevent(bdev, KOBJ_MOUNT);
+		bdev->bd_super = s;
 	}
 
-	return simple_set_mnt(mnt, s);
+	simple_set_mnt(mnt, s);
+	return 0;
 
 error_s:
 	error = PTR_ERR(s);
 error_bdev:
-	close_bdev_excl(bdev);
+	close_bdev_exclusive(bdev, mode);
 error:
 	return error;
 }
@@ -779,14 +920,16 @@ EXPORT_SYMBOL(get_sb_bdev);
 void kill_block_super(struct super_block *sb)
 {
 	struct block_device *bdev = sb->s_bdev;
+	fmode_t mode = sb->s_mode;
 
-	bdev_uevent(bdev, KOBJ_UMOUNT);
+	bdev->bd_super = NULL;
 	generic_shutdown_super(sb);
 	sync_blockdev(bdev);
-	close_bdev_excl(bdev);
+	close_bdev_exclusive(bdev, mode);
 }
 
 EXPORT_SYMBOL(kill_block_super);
+#endif
 
 int get_sb_nodev(struct file_system_type *fs_type,
 	int flags, void *data,
@@ -803,12 +946,12 @@ int get_sb_nodev(struct file_system_type *fs_type,
 
 	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 	if (error) {
-		up_write(&s->s_umount);
-		deactivate_super(s);
+		deactivate_locked_super(s);
 		return error;
 	}
 	s->s_flags |= MS_ACTIVE;
-	return simple_set_mnt(mnt, s);
+	simple_set_mnt(mnt, s);
+	return 0;
 }
 
 EXPORT_SYMBOL(get_sb_nodev);
@@ -833,14 +976,14 @@ int get_sb_single(struct file_system_type *fs_type,
 		s->s_flags = flags;
 		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 		if (error) {
-			up_write(&s->s_umount);
-			deactivate_super(s);
+			deactivate_locked_super(s);
 			return error;
 		}
 		s->s_flags |= MS_ACTIVE;
 	}
 	do_remount_sb(s, flags, data, 0);
-	return simple_set_mnt(mnt, s);
+	simple_set_mnt(mnt, s);
+	return 0;
 }
 
 EXPORT_SYMBOL(get_sb_single);
@@ -860,12 +1003,12 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
 	if (!mnt)
 		goto out;
 
-	if (data) {
+	if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
 		secdata = alloc_secdata();
 		if (!secdata)
 			goto out_mnt;
 
-		error = security_sb_copy_data(type, data, secdata);
+		error = security_sb_copy_data(data, secdata);
 		if (error)
 			goto out_free_secdata;
 	}
@@ -873,8 +1016,9 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
 	error = type->get_sb(type, flags, name, data, mnt);
 	if (error < 0)
 		goto out_free_secdata;
+	BUG_ON(!mnt->mnt_sb);
 
- 	error = security_sb_kern_mount(mnt->mnt_sb, secdata);
+ 	error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
  	if (error)
  		goto out_sb;
 
@@ -885,8 +1029,7 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
 	return mnt;
 out_sb:
 	dput(mnt->mnt_root);
-	up_write(&mnt->mnt_sb->s_umount);
-	deactivate_super(mnt->mnt_sb);
+	deactivate_locked_super(mnt->mnt_sb);
 out_free_secdata:
 	free_secdata(secdata);
 out_mnt:
@@ -897,6 +1040,29 @@ out:
 
 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 
+static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
+{
+	int err;
+	const char *subtype = strchr(fstype, '.');
+	if (subtype) {
+		subtype++;
+		err = -EINVAL;
+		if (!subtype[0])
+			goto err;
+	} else
+		subtype = "";
+
+	mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
+	err = -ENOMEM;
+	if (!mnt->mnt_sb->s_subtype)
+		goto err;
+	return mnt;
+
+ err:
+	mntput(mnt);
+	return ERR_PTR(err);
+}
+
 struct vfsmount *
 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 {
@@ -905,13 +1071,17 @@ do_kern_mount(const char *fstype, int flags, const char *name, void *data)
 	if (!type)
 		return ERR_PTR(-ENODEV);
 	mnt = vfs_kern_mount(type, flags, name, data);
+	if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
+	    !mnt->mnt_sb->s_subtype)
+		mnt = fs_set_subtype(mnt, fstype);
 	put_filesystem(type);
 	return mnt;
 }
+EXPORT_SYMBOL_GPL(do_kern_mount);
 
-struct vfsmount *kern_mount(struct file_system_type *type)
+struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
 {
-	return vfs_kern_mount(type, 0, type->name, NULL);
+	return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
 }
 
-EXPORT_SYMBOL(kern_mount);
+EXPORT_SYMBOL_GPL(kern_mount_data);