in 5.5: The kernel crypto API was significantly reworked.
This impacts the adler32 and gss
in 5.5: Changed struct jbd2_journal_handle
Members h_buffer_credits* changed to h_revoke_credits*
In 5.6: procfs changed from file_operations to proc_ops
This impacts all users of procfs and a few places where procfs and debugfs usages are interchanged as well as some structures that contain file_operations vs proc_ops.
In 5.6: time_t is removed.
All users are expected to shift to time64_t. For the majority of cases this is just a name change (64 bit architectures have been using 'long' for time_t for a very long time.
However this does impact 32 bit architectures and inter-op where time_t was not enforced to 64 bit previously needs to be resolved.
In 5.6: timespec*_trunc is removed.
It's not very useful so the one usage can probably be dropped entirely.