Rebase to v3.12-rc5
Add more v3.12 stable patches
add patch ratelimit-ext4-messages
add patch pair-trace-ext4_writepages_and-trace_ext4_writepages_result
add patch fix-the-ext4_read_inline_dir-return-value
add patch mbcache-decouple-locking-from-global-data and
each-fs-creates-its-own-mb_cache to the unstable series
add patch drop-unused-reclen-variable-from-ext4_add_dirent_to_inline
add patch fix-FITRIM-in-no-journal-mode
add patch dont-count-free-clusters-from-a-corrupt-block-group
add commit avoid-bh-leak-in-retry-path-of-ext4_expand_extra_isize_ea
add commit fiemap_discard
add patch remove-unreachable-code-in-ext4_can_extents_be_merged
add patch remove-unreachable-code-after-ext4_can_extents_be_merged
add patch fix-reading-of-extended-tv_sec
add patch use-prandom_u32-instead-of-get_random_bytes
replace fiemap_discard with add-blkdiscard-ioctl