Branch b1_6

b=12861
i=alex
i=adilger
i=kalpak

Severity   : major
Bugzilla   : 12861
Description: ldiskfs_ext_search_right: bad header in inode #3981353: unexpected
	     eh_depth
Details    : a wrong check of extent headers in ldiskfs_ext_search_right()
	     can cause the filesystem to be remounted read-only.