Illumos #952: separate intent logs should be obvious in 'zpool iostat' output

Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Reviewed by: Garrett D'Amore <garrett@nexenta.com>
Approved by: Eric Schrock <eric.schrock@delphix.com>

Refererce to Illumos issue:
  https://www.illumos.org/issues/952

Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #607
Illumos #1946: incorrect formatting when listing output of multiple pools with zpool iostat -v

Reviewed by: Richard Elling <richard.elling@richardelling.com>
Reviewed by: Joshua M. Clulow <josh@sysmgr.org>
Approved by: Richard Lowe <richlowe@richlowe.net>

Reference to Illumos issue:
  https://www.illumos.org/issues/1946

Ported by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Illumos #2067: uninitialized variables in zfs(1M) may make snapshots undestroyable

Reviewed by: Joshua M. Clulow <josh@sysmgr.org>
Reviewed by: Milan Jurik <milan.jurik@xylab.cz>
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Steve Gonczi <gonczi@comcast.net>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
	https://www.illumos.org/issues/2067

Ported by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Add zfs_mdcomp_disable module option

Expose the zfs_mdcomp_disable variable as a module option.  This
can be used to disable compression of zfs meta data which is
enabled by default.  This shouldn't need to be tuned but for
most workloads, however there may be very specific instances
where it makes sense to trade disk capacity for extra cpu cycles.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Integrate ARC more tightly with Linux

Under Solaris the ARC was designed to stay one step ahead of the
VM subsystem.  It would attempt to recognize low memory situtions
before they occured and evict data from the cache.  It would also
make assessments about if there was enough free memory to perform
a specific operation.

This was all possible because Solaris exposes a fairly decent
view of the memory state of the system to other kernel threads.
Linux on the other hand does not make this information easily
available.  To avoid extensive modifications to the ARC the SPL
attempts to provide these same interfaces.  While this works it
is not ideal and problems can arise when the ARC and Linux have
different ideas about when your out of memory.  This has manifested
itself in the past as a spinning arc_reclaim_thread.

This patch abandons the emulated Solaris interfaces in favor of
the prefered Linux interface.  That means moving the bulk of the
memory reclaim logic out of the arc_reclaim_thread and in to the
evict driven shrinker callback.  The Linux VM will call this
function when it needs memory.  The ARC is then responsible for
attempting to free the requested amount of memory if possible.

Several interfaces have been modified to accomidate this approach,
however the basic user space implementation remains the same.
The following changes almost exclusively just apply to the kernel
implementation.

* Removed the hdr_recl() reclaim callback which is redundant
  with the broader arc_shrinker_func().

* Reduced arc_grow_retry to 5 seconds from 60.  This is now used
  internally in the ARC with arc_no_grow to indicate that direct
  reclaim was recently performed.  This typically indicates a
  rapid change in memory demands which the kswapd threads were
  unable to keep ahead of.  As long as direct reclaim is happening
  once every 5 seconds arc growth will be paused to avoid further
  contributing to the existing memory pressure.  The more common
  indirect reclaim paths will not set arc_no_grow.

* arc_shrink() has been extended to take the number of bytes by
  which arc_c should be reduced.  This allows for a more granual
  reduction of the arc target.  Since the kernel provides a
  reclaim value to the arc_shrinker_func() this value is used
  instead of 1<<arc_shrink_shift.

* arc_reclaim_needed() has been removed.  It was used to determine
  if the system was under memory pressure and relied extensively
  on Solaris specific VM interfaces.  In most case the new code
  just checks arc_no_grow which indicates that within the last
  arc_grow_retry seconds direct memory reclaim occurred.

* arc_memory_throttle() has been updated to always include the
  amount of evictable memory (arc and page cache) in its free
  space calculations.  This space is largely available in most
  call paths due to direct memory reclaim.

* The Solaris pageout code was also removed to avoid confusion.
  It has always been disabled due to proc_pageout being defined
  as NULL in the Linux port.

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Update ARC memory limits to account for SLUB internal fragmentation

23bdb07d4e4c435205d25d3efdb5fef2d089ce5e updated the ARC memory limits
to be 1/2 of memory or all but 4GB. Unfortunately, these values assume
zero internal fragmentation in the SLUB allocator, when in reality, the
internal fragmentation could be as high as 50%, effectively doubling
memory usage. This poses clear safety issues, because it permits the
size of ARC to exceed system memory.

This patch changes this so that the default value of arc_c_max is always
1/2 of system memory. This effectively limits the ARC to the memory that
the system has physically installed.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #660
Disable direct reclaim on zvols

Previously, it was possible for the direct reclaim path to be invoked
when a write to a zvol was made. When a zvol is used as a swap device,
this often causes swap requests to depend on additional swap requests,
which deadlocks. We address this by disabling the direct reclaim path
on zvols.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #342
Linux 3.3 compat, iops->create()/mkdir()/mknod()

The mode argument of iops->create()/mkdir()/mknod() was changed from
an 'int' to a 'umode_t'.  To prevent a compiler warning an autoconf
check was added to detect the API change and then correctly set a
zpl_umode_t typedef.  There is no functional change.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #701
Add mdadm and bc dependencies

The zfs-test package additionally depends on mdadm and bc to
run the zfault.sh tests.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #690
Revert "Disable direct reclaim on zvols"

This reverts commit ce90208cf9e04df966429f115d8831371ea9afce.  This
change was observed to cause problems when using a zvol to back a VM
under 2.6.32.59 kernels.  This issue was filed as #710.

Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #342
Issue #710
Add vdev_id for JBOD-friendly udev aliases

vdev_id parses the file /etc/zfs/vdev_id.conf to map a physical path
in a storage topology to a channel name.  The channel name is combined
with a disk enclosure slot number to create an alias that reflects the
physical location of the drive.  This is particularly helpful when it
comes to tasks like replacing failed drives.  Slot numbers may also be
re-mapped in case the default numbering is unsatisfactory.  The drive
aliases will be created as symbolic links in /dev/disk/by-vdev.

The only currently supported topologies are sas_direct and sas_switch.
A multipath mode is supported in which dm-mpath devices are handled by
examining the first-listed running component disk.  Multipath mode
relies on earlier udev rules that export the variable DM_NAME, which
may not be supported on non-Red Hat distributions.  In multipath mode
the configuration file should contain a channel definition with the
same name for each path to a given enclosure.

vdev_id can replace the existing zpool_id script on systems where the
storage topology conforms to one of the supported modes, sas_direct or
sas_switch.  The script could be extended to support other topologies
as well.  The advantage of vdev_id is that it is driven by a single
static input file that can be shared across multiple nodes having a
common storage toplogy.  zpool_id, on the other hand, requires a
unique /etc/zfs/zdev.conf per node and a separate slot-mapping file.
However, zpool_id provides the flexibility of using any device names
that show up in /dev/disk/by-path, so it may still be needed on some
systems.

vdev_id's functionality subsumes that of the sas_switch_id script, so
that script is removed since it is unlikely anyone is using it.

Finally, add /dev/disk/by-vdev to the list of directories that
'zpool import' will scan.