[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>
diff --git a/arch/mips/kernel/sysirix.c b/arch/mips/kernel/sysirix.c
index 5407b78..19e1ef4 100644
--- a/arch/mips/kernel/sysirix.c
+++ b/arch/mips/kernel/sysirix.c
@@ -694,7 +694,7 @@
 	if (error)
 		goto out;
 
-	error = vfs_statfs(nd.dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(nd.dentry, &kbuf);
 	if (error)
 		goto dput_and_out;
 
@@ -732,7 +732,7 @@
 		goto out;
 	}
 
-	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(file->f_dentry, &kbuf);
 	if (error)
 		goto out_f;
 
@@ -1360,7 +1360,7 @@
 	error = user_path_walk(fname, &nd);
 	if (error)
 		goto out;
-	error = vfs_statfs(nd.dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(nd.dentry, &kbuf);
 	if (error)
 		goto dput_and_out;
 
@@ -1406,7 +1406,7 @@
 		error = -EBADF;
 		goto out;
 	}
-	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(file->f_dentry, &kbuf);
 	if (error)
 		goto out_f;
 
@@ -1611,7 +1611,7 @@
 	error = user_path_walk(fname, &nd);
 	if (error)
 		goto out;
-	error = vfs_statfs(nd.dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(nd.dentry, &kbuf);
 	if (error)
 		goto dput_and_out;
 
@@ -1658,7 +1658,7 @@
 		error = -EBADF;
 		goto out;
 	}
-	error = vfs_statfs(file->f_dentry->d_inode->i_sb, &kbuf);
+	error = vfs_statfs(file->f_dentry, &kbuf);
 	if (error)
 		goto out_f;