[PATCH] fuse: add support for block device based filesystems

I never intended this, but people started using fuse to implement block device
based "real" filesystems (ntfs-3g, zfs).

The following four patches add better support for these kinds of filesystems.
Unlike "normal" fuse filesystems, using this feature should require superuser
privileges (enforced by the fusermount utility).

Thanks to Szabolcs Szakacsits for the input and testing.

This patch adds a 'fuseblk' filesystem type, which is only different from the
'fuse' filesystem type in how the 'dev_name' mount argument is interpreted.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 37 insertions, 11 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 2bdc652b8b46..38cf97d6469c 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -591,6 +591,14 @@ static int fuse_get_sb(struct file_system_type *fs_type,
 	return get_sb_nodev(fs_type, flags, raw_data, fuse_fill_super, mnt);
 }
 
+static int fuse_get_sb_blk(struct file_system_type *fs_type,
+			   int flags, const char *dev_name,
+			   void *raw_data, struct vfsmount *mnt)
+{
+	return get_sb_bdev(fs_type, flags, dev_name, raw_data, fuse_fill_super,
+			   mnt);
+}
+
 static struct file_system_type fuse_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "fuse",
@@ -598,6 +606,14 @@ static struct file_system_type fuse_fs_type = {
 	.kill_sb	= kill_anon_super,
 };
 
+static struct file_system_type fuseblk_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "fuseblk",
+	.get_sb		= fuse_get_sb_blk,
+	.kill_sb	= kill_block_super,
+	.fs_flags	= FS_REQUIRES_DEV,
+};
+
 static decl_subsys(fuse, NULL, NULL);
 static decl_subsys(connections, NULL, NULL);
 
@@ -617,24 +633,34 @@ static int __init fuse_fs_init(void)
 
 	err = register_filesystem(&fuse_fs_type);
 	if (err)
-		printk("fuse: failed to register filesystem\n");
-	else {
-		fuse_inode_cachep = kmem_cache_create("fuse_inode",
-						      sizeof(struct fuse_inode),
-						      0, SLAB_HWCACHE_ALIGN,
-						      fuse_inode_init_once, NULL);
-		if (!fuse_inode_cachep) {
-			unregister_filesystem(&fuse_fs_type);
-			err = -ENOMEM;
-		}
-	}
+		goto out;
+
+	err = register_filesystem(&fuseblk_fs_type);
+	if (err)
+		goto out_unreg;
+
+	fuse_inode_cachep = kmem_cache_create("fuse_inode",
+					      sizeof(struct fuse_inode),
+					      0, SLAB_HWCACHE_ALIGN,
+					      fuse_inode_init_once, NULL);
+	err = -ENOMEM;
+	if (!fuse_inode_cachep)
+		goto out_unreg2;
+
+	return 0;
 
+ out_unreg2:
+	unregister_filesystem(&fuseblk_fs_type);
+ out_unreg:
+	unregister_filesystem(&fuse_fs_type);
+ out:
 	return err;
 }
 
 static void fuse_fs_cleanup(void)
 {
 	unregister_filesystem(&fuse_fs_type);
+	unregister_filesystem(&fuseblk_fs_type);
 	kmem_cache_destroy(fuse_inode_cachep);
 }