Linux 3.12 compat: shrinker semantics

The new shrinker API as of Linux 3.12 modifies "struct shrinker" by
replacing the @shrink callback with the pair of @count_objects and
@scan_objects.  It also requires the return value of @count_objects to
return the number of objects actually freed whereas the previous @shrink
callback returned the number of remaining freeable objects.

This patch adds support for the new @scan_objects return value semantics.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes #2837
Kernel header installation should respect --prefix

This is the upstream component of work that enables preliminary support
for building Gentoo's ZFS packaging on other Linux systems via Gentoo
Prefix.

Signed-off-by: Richard Yao <richard.yao@clusterhq.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2641
Search /usr/local/src for SPL Object Directory

Since we changed the default location for the kernel headers to respect
--prefix in the SPL, we must search that location to prevent user builds
from breaking.

Signed-off-by: Richard Yao <richard.yao@clusterhq.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2641
Make directory into which mount.zfs is installed configurable

Installing outside of the prefix is not permissible under Gentoo Prefix.
The package manager will cause the installation process to fail if/when
it sees this. I could script a workaround inside the ebuild, but it
seemed to make more sense to make this more configurable.

Signed-off-by: Richard Yao <richard.yao@clusterhq.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2641
Make systemd-modules-load.service file directory configurable

Installing outside of the prefix is not permissible under Gentoo Prefix.
The package manager will cause the installation process to fail if/when
it sees this. We could handle this by disabling systemd support on
prefix because systemd does not check these paths, but the Gentoo
Council decided that small files such as these should be installed.
That means disabling systemd support on prefix is not an acceptable
workaround. As a consequence, we need some way of control the directory
into which these files are installed.

Making this configurable increases our compliance with the
freedesktop.org specification, which allows these files to be installed
into /etc/modules-load.d:

http://www.freedesktop.org/software/systemd/man/modules-load.d.html

Signed-off-by: Richard Yao <richard.yao@clusterhq.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2641
Fix modules installation directory

When building zfs modules with kernel, compiled from deb.src, the
packaging process ends up installing the modules in the wrong place.

Signed-off-by: Alexander Pyhalov <apyhalov@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2822
Add config/compile to config/.gitignore

This file may be added by automake and therefore should be added
to config/.gitignore.  For the full list of possible auxiliary
programs see the full automake documentation.

http://www.gnu.org/software/automake/manual/automake.html#Auxiliary-Programs

Signed-off-by: Marcel Wysocki <maci.stgn@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2848
Improve zvol symlink handling.

Change the zvol helper program to replace any embedded spaces
in the pool or dataset names with '+' to ensure we have valid
symlinks.

The '+' character was choosen because it is not a valid character
for a dataset name but it is allowed by udev.  This ensures that
all dataset names with an embedded space will be translated to
a unique /dev/zvol/ symlink.

Signed-off-by: Dan Swartzendruber <dswartz@druber.com>
Signed-off-by: Darik Horn <dajhorn@vanadac.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2834
Export symbols for ZIL interface

These symbols are needed by consumers (i.e. Lustre) who wish to
integrate with the ZIL.  In addition the zil_rollback_destroy()
prototype was removed because the implementation of this function
was removed long ago.

Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2892
Reduce buf/dbuf mutex contention

Due to evidence of contention both the buf_hash_table and the
dbuf_hash_table sizes have been increased from 256 to 8192.

This increase in hash table size adds approximating 0.5M to
our fixed memory footprint.  This relatively small increase
is not expected to cause problems even on low memory machines.
This footprint will also become dynamic when the persistent
L2ARC support is finalized.  In the meanwhile, this small
change significantly reduces contention for certain workloads.

Signed-off-by: Chris Wedgwood <cw@f00f.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Pavel Snajdr <snajpa@snajpa.net>
Closes #1291
Fix inaccurate field descriptions

The field descriptions from arcstat.py -v for the demand accesses
are inaccurate. They all begin with "Demand Data" yet the fields
actually covered both demand data and demand meta-data accesses.

Signed-off-by: Isaac Huang <he.huang@intel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2842
Print header properly when terminal resizes

Added a handler for SIGWINCH, so that one header
is printed per screen even when the terminal resizes.

Signed-off-by: Isaac Huang <he.huang@intel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2847
Illumos 5213 - panic in metaslab_init due to space_map_open returning ENXIO

5213 panic in metaslab_init due to space_map_open returning ENXIO
Reviewed by: Matthew Ahrens mahrens@delphix.com
Reviewed by: George Wilson george.wilson@delphix.com

References:
  https://www.illumos.org/issues/5213
  https://reviews.csiden.org/r/110

Porting notes:

For the Linux port, KM_SLEEP was replaced with KM_PUSHPAGE.

Ported by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2745
Fix small spelling mistake

recieve becomes receive

Signed-off-by: Randall Mason <ClashTheBunny@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2877
Move a few internal ARC strucutres to arc_impl.h

Add a new file named arc_impl.h and move a few internal
ARC structure definitions into this file. This is
needed in order to allow the Linux tracepoint functions to grub
around in the internals of these structures.

Signed-off-by: Prakash Surya <prakash.surya@delphix.com>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fix dprintf format specifiers

Fix a few dprintf format specifiers that disagreed with their argument
types.  These came to light as compiler errors when converting dprintf
to use the Linux trace buffer.  Previously this wasn't a problem,
presumably because the SPL debug logging uses vsnprintf which must
perform automatic type conversion.

Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
cstyle: allow right paren on its own line

Make the style checker script accept right parentheses on their own
lines. This is motivated by the Linux tracepoints macro
DECLARE_EVENT_CLASS.

The code within TP_fast_assign() (a parameter of DECLARE_EVENT_CLASS)
is normal C assignments terminated by semicolons.  But the style
checker forbids us from following a semicolon with a non-blank and
from preceding a right parenthesis with white space.  Therefore the
closing parenthesis must go on the next line, yet the style checker
foribs us from indenting it for readability.  Relaxing the
no-non-blank-after-semicolon rule would open the door to too many bad
style practices. So instead we relax the
no-white-space-before-right-paren rule if the parenthesis is on its
own line.  The relaxation is overriden with the -p option so we still
have a way to catch misuse of this style.

Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Swap DTRACE_PROBE* with Linux tracepoints

This patch leverages Linux tracepoints from within the ZFS on Linux
code base. It also refactors the debug code to bring it back in sync
with Illumos.

The information exported via tracepoints can be used for a variety of
reasons (e.g. debugging, tuning, general exploration/understanding,
etc). It is advantageous to use Linux tracepoints as the mechanism to
export this kind of information (as opposed to something else) for a
number of reasons:

    * A number of external tools can make use of our tracepoints
      "automatically" (e.g. perf, systemtap)
    * Tracepoints are designed to be extremely cheap when disabled
    * It's one of the "accepted" ways to export this kind of
      information; many other kernel subsystems use tracepoints too.

Unfortunately, though, there are a few caveats as well:

    * Linux tracepoints appear to only be available to GPL licensed
      modules due to the way certain kernel functions are exported.
      Thus, to actually make use of the tracepoints introduced by this
      patch, one might have to patch and re-compile the kernel;
      exporting the necessary functions to non-GPL modules.

    * Prior to upstream kernel version v3.14-rc6-30-g66cc69e, Linux
      tracepoints are not available for unsigned kernel modules
      (tracepoints will get disabled due to the module's 'F' taint).
      Thus, one either has to sign the zfs kernel module prior to
      loading it, or use a kernel versioned v3.14-rc6-30-g66cc69e or
      newer.

Assuming the above two requirements are satisfied, lets look at an
example of how this patch can be used and what information it exposes
(all commands run as 'root'):

    # list all zfs tracepoints available

    $ ls /sys/kernel/debug/tracing/events/zfs
    enable              filter              zfs_arc__delete
    zfs_arc__evict      zfs_arc__hit        zfs_arc__miss
    zfs_l2arc__evict    zfs_l2arc__hit      zfs_l2arc__iodone
    zfs_l2arc__miss     zfs_l2arc__read     zfs_l2arc__write
    zfs_new_state__mfu  zfs_new_state__mru

    # enable all zfs tracepoints, clear the tracepoint ring buffer

    $ echo 1 > /sys/kernel/debug/tracing/events/zfs/enable
    $ echo 0 > /sys/kernel/debug/tracing/trace

    # import zpool called 'tank', inspect tracepoint data (each line was
    # truncated, they're too long for a commit message otherwise)

    $ zpool import tank
    $ cat /sys/kernel/debug/tracing/trace | head -n35
    # tracer: nop
    #
    # entries-in-buffer/entries-written: 1219/1219   #P:8
    #
    #                              _-----=> irqs-off
    #                             / _----=> need-resched
    #                            | / _---=> hardirq/softirq
    #                            || / _--=> preempt-depth
    #                            ||| /     delay
    #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
    #              | |       |   ||||       |         |
            lt-zpool-30132 [003] .... 91344.200050: zfs_arc__miss: hdr...
          z_rd_int/0-30156 [003] .... 91344.200611: zfs_new_state__mru...
            lt-zpool-30132 [003] .... 91344.201173: zfs_arc__miss: hdr...
          z_rd_int/1-30157 [003] .... 91344.201756: zfs_new_state__mru...
            lt-zpool-30132 [003] .... 91344.201795: zfs_arc__miss: hdr...
          z_rd_int/2-30158 [003] .... 91344.202099: zfs_new_state__mru...
            lt-zpool-30132 [003] .... 91344.202126: zfs_arc__hit: hdr ...
            lt-zpool-30132 [003] .... 91344.202130: zfs_arc__hit: hdr ...
            lt-zpool-30132 [003] .... 91344.202134: zfs_arc__hit: hdr ...
            lt-zpool-30132 [003] .... 91344.202146: zfs_arc__miss: hdr...
          z_rd_int/3-30159 [003] .... 91344.202457: zfs_new_state__mru...
            lt-zpool-30132 [003] .... 91344.202484: zfs_arc__miss: hdr...
          z_rd_int/4-30160 [003] .... 91344.202866: zfs_new_state__mru...
            lt-zpool-30132 [003] .... 91344.202891: zfs_arc__hit: hdr ...
            lt-zpool-30132 [001] .... 91344.203034: zfs_arc__miss: hdr...
          z_rd_iss/1-30149 [001] .... 91344.203749: zfs_new_state__mru...
            lt-zpool-30132 [001] .... 91344.203789: zfs_arc__hit: hdr ...
            lt-zpool-30132 [001] .... 91344.203878: zfs_arc__miss: hdr...
          z_rd_iss/3-30151 [001] .... 91344.204315: zfs_new_state__mru...
            lt-zpool-30132 [001] .... 91344.204332: zfs_arc__hit: hdr ...
            lt-zpool-30132 [001] .... 91344.204337: zfs_arc__hit: hdr ...
            lt-zpool-30132 [001] .... 91344.204352: zfs_arc__hit: hdr ...
            lt-zpool-30132 [001] .... 91344.204356: zfs_arc__hit: hdr ...
            lt-zpool-30132 [001] .... 91344.204360: zfs_arc__hit: hdr ...

To highlight the kind of detailed information that is being exported
using this infrastructure, I've taken the first tracepoint line from the
output above and reformatted it such that it fits in 80 columns:

    lt-zpool-30132 [003] .... 91344.200050: zfs_arc__miss:
        hdr {
            dva 0x1:0x40082
            birth 15491
            cksum0 0x163edbff3a
            flags 0x640
            datacnt 1
            type 1
            size 2048
            spa 3133524293419867460
            state_type 0
            access 0
            mru_hits 0
            mru_ghost_hits 0
            mfu_hits 0
            mfu_ghost_hits 0
            l2_hits 0
            refcount 1
        } bp {
            dva0 0x1:0x40082
            dva1 0x1:0x3000e5
            dva2 0x1:0x5a006e
            cksum 0x163edbff3a:0x75af30b3dd6:0x1499263ff5f2b:0x288bd118815e00
            lsize 2048
        } zb {
            objset 0
            object 0
            level -1
            blkid 0
        }

For the specific tracepoint shown here, 'zfs_arc__miss', data is
exported detailing the arc_buf_hdr_t (hdr), blkptr_t (bp), and
zbookmark_t (zb) that caused the ARC miss (down to the exact DVA!).
This kind of precise and detailed information can be extremely valuable
when trying to answer certain kinds of questions.

For anybody unfamiliar but looking to build on this, I found the XFS
source code along with the following three web links to be extremely
helpful:

    * http://lwn.net/Articles/379903/
    * http://lwn.net/Articles/381064/
    * http://lwn.net/Articles/383362/

I should also node the more "boring" aspects of this patch:

    * The ZFS_LINUX_COMPILE_IFELSE autoconf macro was modified to
       support a sixth paramter. This parameter is used to populate the
       contents of the new conftest.h file. If no sixth parameter is
       provided, conftest.h will be empty.

    * The ZFS_LINUX_TRY_COMPILE_HEADER autoconf macro was introduced.
      This macro is nearly identical to the ZFS_LINUX_TRY_COMPILE macro,
      except it has support for a fifth option that is then passed as
      the sixth parameter to ZFS_LINUX_COMPILE_IFELSE.

These autoconf changes were needed to test the availability of the Linux
tracepoint macros. Due to the odd nature of the Linux tracepoint macro
API, a separate ".h" must be created (the path and filename is used
internally by the kernel's define_trace.h file).

    * The HAVE_DECLARE_EVENT_CLASS autoconf macro was introduced. This
      is to determine if we can safely enable the Linux tracepoint
      functionality. We need to selectively disable the tracepoint code
      due to the kernel exporting certain functions as GPL only. Without
      this check, the build process will fail at link time.

In addition, the SET_ERROR macro was modified into a tracepoint as well.
To do this, the 'sdt.h' file was moved into the 'include/sys' directory
and now contains a userspace portion and a kernel space portion. The
dprintf and zfs_dbgmsg* interfaces are now implemented as tracepoint as
well.

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Merge branch 'b_tracepoints'

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2874
Undirty freed spill blocks.

If a spill block's dbuf hasn't yet been written when a spill block is
freed, the unwritten version will still be written.  This patch handles
the case in which a spill block's dbuf is freed and undirties it to
prevent it from being written.

The most common case in which this could happen is when xattr=sa is being
used and a long xattr is immediately replaced by a short xattr as in:

	setfattr -n user.test -v very_very_very..._long_value  <file>
	setfattr -n user.test -v short_value  <file>

The first value must be sufficiently long that a spill block is generated
and the second value must be short enough to not require a spill block.
In practice, this would typically happen due to internal xattr operations
as a result of setting acltype=posixacl.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2663
Closes #2700
Closes #2701
Closes #2717
Closes #2863
Closes #2884