Add cv_wait_io() to account I/O time

Under Linux when a task is waiting on I/O it should call the
io_schedule() function for proper accounting.  The Solaris
cv_wait() function provides no way to specify what the cv
is waiting on therefore cv_wait_io() is introduced.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #206
RHEL 6.4 compat, fallocate()

In the upstream kernel the FALLOC_FL_PUNCH_HOLE #define was
introduced after the fallocate() function was moved from the
inode_operations to the file_operations structure.  Therefore,
the SPL code assumed that if FALLOC_FL_PUNCH_HOLE was defined
it was safe to use f_ops->fallocate().

Unfortunately, the RHEL6.4 kernel has only backported the
FALLOC_FL_PUNCH_HOLE #define and not the fallocate() change.

To address this compatibility issue the spl_filp_fallocate()
helper function was added to properly detect which interface
is available.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Linux compat 3.7.1, on_each_cpu()

Some kernels require that we include the 'linux/irqflags.h'
header for the SPL_AC_3ARGS_ON_EACH_CPU check.  Otherwise,
the functions local_irq_enable()/local_irq_disable() will not
be defined and the prototype will be misdetected as the four
argument version.

This change actually include 'linux/interrupt.h' which in turn
includes 'linux/irqflags.h' to be as generic as possible.

Additionally, passing NULL as the function can result in a
gcc error because the on_each_cpu() macro executes it
unconditionally.  To make the test more robust we pass the
dummy function on_each_cpu_func().

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #204
Check for ZLIB_INFLATE and ZLIB_DEFLATE

Check at ./configure time that the kernel was built with zlib
support enabled.  This support may either be configured as a
module or builtin to the kernel.  But if it's missing the build
will fail so it's best to catch this early.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes zfsonlinux/zfs#582
call_usermodehelper() should wait for process

As of Linux 3.4 the UMH_WAIT_* constants were renumbered.  In
particular, the meaning of "1" changed from UMH_WAIT_PROC (wait for
process to complete), to UMH_WAIT_EXEC (wait for the exec, but not the
process).  A number of call sites used the number 1 instead of the
constant name, so the behavior was not as expected on kernels with
this change.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Merge remote-tracking branch 'upstream/master'