[PATCH] VFS: Permit filesystem to perform statfs with a known root dentry

Give the statfs superblock operation a dentry pointer rather than a superblock
pointer.

This complements the get_sb() patch.  That reduced the significance of
sb->s_root, allowing NFS to place a fake root there.  However, NFS does
require a dentry to use as a target for the statfs operation.  This permits
the root in the vfsmount to be used instead.

linux/mount.h has been added where necessary to make allyesconfig build
successfully.

Interest has also been expressed for use with the FUSE and XFS filesystems.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nathan Scott <nathans@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/jffs/inode-v23.c

@@ -377,9 +377,9 @@ jffs_new_inode(const struct inode * dir, struct jffs_raw_inode *raw_inode,
 
 /* Get statistics of the file system.  */
 static int
-jffs_statfs(struct super_block *sb, struct kstatfs *buf)
+jffs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
-	struct jffs_control *c = (struct jffs_control *) sb->s_fs_info;
+	struct jffs_control *c = (struct jffs_control *) dentry->d_sb->s_fs_info;
 	struct jffs_fmcontrol *fmc;
 
 	lock_kernel();