mm/hugetlbfs: fix error handling when setting up mounts

mm/hugetlbfs: fix error handling when setting up mounts

It is assumed that the hugetlbfs_vfsmount[] array will contain either a
valid vfsmount pointer or NULL for each hstate after initialization.
Changes made while converting to use fs_context broke this assumption.

While fixing the hugetlbfs_vfsmount issue, it was discovered that
init_hugetlbfs_fs never did correctly clean up when encountering a vfs
mount error.

It was found during code inspection.  A small memory allocation failure
would be the most likely cause of taking a error path with the bug.
This is unlikely to happen as this is early init code.

Link: http://lkml.kernel.org/r/94b6244d-2c24-e269-b12c-e3ba694b242d@oracle.com
Reported-by: Chengguang Xu <cgxu519@mykernel.net>
Fixes: 32021982a324 ("hugetlbfs: Convert to fs_context")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>