Mark IO pipeline with PF_FSTRANS

In order to avoid deadlocking in the IO pipeline it is critical that
pageout be avoided during direct memory reclaim.  This ensures that
the pipeline threads can always make forward progress and never end
up blocking on a DMU transaction.  For this very reason Linux now
provides the PF_FSTRANS flag which may be set in the process context.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Use is_vmalloc_addr() in vdev_disk.c

The initial port of ZFS to Linux required a way to identify virtual
memory to make IO to virtual memory backed slabs work, so kmem_virt()
was created. Linux 2.6.25 introduced is_vmalloc_addr(), which is
logically equivalent to kmem_virt(). Support for kernels before 2.6.26
was later dropped and more recently, support for kernels before Linux
2.6.32 has been dropped. We retire kmem_virt() in favor of
is_vmalloc_addr() to cleanup the code.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Retire KM_NODEBUG

Callers of kmem_alloc() which passed the KM_NODEBUG flag to suppress
the large allocation warning have been replaced by vmem_alloc() as
appropriate.  The updated vmem_alloc() call will not print a warning
regardless of the size of the allocation.

A careful reader will notice that not all callers have been changed
to vmem_alloc().  Some have only had the KM_NODEBUG flag removed.
This was possible because the default warning threshold has been
increased to 32k.  This is desirable because it minimizes the need
for Linux specific code changes.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Change KM_PUSHPAGE -> KM_SLEEP

By marking DMU transaction processing contexts with PF_FSTRANS
we can revert the KM_PUSHPAGE -> KM_SLEEP changes.  This brings
us back in line with upstream.  In some cases this means simply
swapping the flags back.  For others fnvlist_alloc() was replaced
by nvlist_alloc(..., KM_PUSHPAGE) and must be reverted back to
fnvlist_alloc() which assumes KM_SLEEP.

The one place KM_PUSHPAGE is kept is when allocating ARC buffers
which allows us to dip in to reserved memory.  This is again the
same as upstream.
Add kmem_cache.h include to default context

As part of the spl kmem/vmem refactoring the kmem_cache_* functions
were split in to their own kmem_cache.h header.  This was done in
part so that kmem_* consumers would not be forced to include the
kmem_cache_* functions which mask several Linux SLAB/SLAB functions.

Because of this we now much explicitly include kmem_cache.h in the
zfs_context.h.  However, consumers such as Lustre which need access
to the KM_FLAGS but not the kmem_cache_* functions can now safely
just include kmem.h.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Revert "Pre-allocate vdev I/O buffers"

Commit 86dd0fd added preallocated I/O buffers.  This is no longer
required after the recent kmem changes designed to make our memory
allocation interfaces behave more like those found on Illumos.  A
deadlock in this situation is no longer possible.

However, these allocations still have the potential to be expensive.
So a potential future optimization might be to perform then KM_NOSLEEP
so that they either succeed of fail quicky.  Either case is acceptable
here because we can safely abort the aggregation.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Revert SA spill block cache

The SA spill_cache was originally introduced to avoid the need to
perform large kmem or vmem allocations.  Instead a small cache of
preallocated SA buffers were kept.  In hindsight, relying on the
existing zio buffer cache is preferable because we are not forced
to assume the worst case allocation size.  This change also has
the benefit of brings the code more in sync with Illumos.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>