Linux 3.17 compat: remove wait_on_bit action function

Linux kernel 3.17 removes the action function argument from
wait_on_bit().  Add autoconf test and compatibility macro to support
the new interface.

The former "wait_on_bit" interface required an 'action' function to
be provided which does the actual waiting. There were over 20 such
functions in the kernel, many of them identical, though most cases
can be satisfied by one of just two functions: one which uses
io_schedule() and one which just uses schedule().  This API change
was made to consolidate all of those redundant wait functions.

References: torvalds/linux@7431620

Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #378
Cleanup vn_rename() and vn_remove()

zfsonlinux/spl#bcb15891ab394e11615eee08bba1fd85ac32e158 implemented
Linux 3.6+ support by adding duplicate vn_rename and vn_remove
functions. The new ones were cleaner, but the duplicate functions made
the codebase less maintainable. This adds some compatibility shims that
allow us to retire the older vn_rename and vn_remove in favor of the new
ones on old kernels. The result is a net 143 line reduction in lines of
code and a cleaner codebase.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #370
Avoid PAGESIZE redefinition

Add #ifndef PAGESIZE to avoid redefinition warning on platforms
where this value is already provided.

Signed-off-by: stf <s@ctrlc.hu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #382
Linux 3.16 compat: smp_mb__after_clear_bit()

The smp_mb__{before,after}_clear_bit functions have been renamed
smp_mb__{before,after}_atomic.  Rather than adding a compatibility
function to handle this the code has been updated to use smp_wmb().

This has the advantage of being a stable functionally equivalent
interface.  On many architectures smp_mb__after_clear_bit() expands
to smp_wmb().  Others might be able to do something slightly more
efficient but this will be safe and correct on all of them.

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #386