[PATCH] Fix for shmem_truncate_range() BUG_ON()

Ran into BUG() while doing madvise(REMOVE) testing.  If we are punching a
hole into shared memory segment using madvise(REMOVE) and the entire hole
is below the indirect blocks, we hit following assert.

	        BUG_ON(limit <= SHMEM_NR_DIRECT);

Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>