Revert part of "Log I/Os longer than zio_delay_max (30s default)"

This reverts commit 9dcb97198338ba2d8764dd5604b278118612f74
which was originally introduced to debug occasional slow I/Os.
These I/Os would complete eventually but were observed to take
several 100 seconds.

The root cause of this issue was the CFQ scheduler which can,
under certain conditions, excessively delay an I/O from being
issued to the device.  This issue was mitigated somewhat by
commit 84daaddedbfc9cf4bd1490d8a6f4b2967051e308 which ensures
the I/O elevator gets changed even for DM style devices.

This change isn't in any way harmful but it does conflict with
a required change to properly account from I/O wait time.
Because Linux does not export the io_schedule_timeout() function
we must instead rely  on io_schedule() via cv_wait_io().

The additional debugging information which was added to the
delay event has been intentionally left in place.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Use cv_wait_io() which will will account for iowait

Update zio_wait() to use cv_wait_io() to ensure the iowait time
is properly accounted for.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Merge branch 'io_schedule'

Currently ZFS doesn't show any I/O time in eg "top" wait% or in
/proc/$pid/stat's blkio_ticks.  Using io_schedule() instead of
schedule() in zio_wait()'s cv_wait() is the correct way to fix
this.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1158
Closes #1175
Fix gcc array subscript above bounds warning

In a debug build, certain GCC versions flag an array bounds warning in
the below code from dnode_sync.c

    } else {
            int i;
            ASSERT(dn->dn_next_nblkptr[txgoff] < dnp->dn_nblkptr);
            /* the blkptrs we are losing better be unallocated */
            for (i = dn->dn_next_nblkptr[txgoff];
                i < dnp->dn_nblkptr; i++)
                    ASSERT(BP_IS_HOLE(&dnp->dn_blkptr[i]));

This usage is in fact safe, since the ASSERT ensures the index does
not exceed to maximum possible number of block pointers. However gcc
can't determine that the assignment 'i = dn->dn_next_nblkptr[txgoff];'
falls within the array bounds so it issues a warning.  To avoid this,
initialize i to zero to make gcc happy but skip the elements before
dn->dn_next_nblkptr[txgoff] in the loop body.  Since a dnode contains
at most 3 block pointers this overhead should be negligible.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #950
Allow fake mounts to succeed on non-legacy filesystems.

mountall in Debian depends on being able to pass the -f parameter to
mount, which specifies a fake mount and just updates the mtab. Currently
mount.zfs will fail such a request if it is not passed with -o zfsutil.

This patch allows a fake mount on a non-legacy filesystem to succeed in
the same manner as a -o remount does, thus enabling mountall to work
correctly.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1167
Fix duplicate words in zpool.8

Remove the duplicate words 'cannot be' from the zpool.8 man page.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1177
Illumos #2619 and #2747

2619 asynchronous destruction of ZFS file systems
2747 SPA versioning with zfs feature flags
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <gwilson@delphix.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Reviewed by: Dan Kruchinin <dan.kruchinin@gmail.com>
Approved by: Eric Schrock <Eric.Schrock@delphix.com>

References:
  illumos/illumos-gate@53089ab7c84db6fb76c16ca50076c147cda11757
  illumos/illumos-gate@ad135b5d644628e791c3188a6ecbd9c257961ef8
  illumos changeset: 13700:2889e2596bd6
  https://www.illumos.org/issues/2619
  https://www.illumos.org/issues/2747

NOTE: The grub specific changes were not ported.  This change
must be made to the Linux grub packages.

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Revert "Temporarily disable the reguid test."

This reverts commit d13524579162b35189804c357a63993be758b84c.
Since feature flags have now been merged we can apply the real
upstream fix from Illumos.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #997
Illumos #3090 and #3102

3090 vdev_reopen() during reguid causes vdev to be treated as corrupt
3102 vdev_uberblock_load() and vdev_validate() may read the wrong label

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Christopher Siden <chris.siden@delphix.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Approved by: Eric Schrock <Eric.Schrock@delphix.com>

References:
  illumos/illumos-gate@dfbb943217bf8ab22a1a9d2e9dca01d4da95ee0b
  illumos changeset: 13777:b1e53580146d
  https://www.illumos.org/issues/3090
  https://www.illumos.org/issues/3102

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #939
Illumos #2762: zpool command should have better support for feature flags

2762 zpool command should have better support for feature flags
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Eric Schrock <Eric.Schrock@delphix.com>

References:
  illumos/illumos-gate@57221772c3fc05faba04bf48ddff45abf2bbf2bd
  https://www.illumos.org/issues/2762

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Illumos #3086: unnecessarily setting DS_FLAG_INCONSISTENT on async

3086 unnecessarily setting DS_FLAG_INCONSISTENT on async
destroyed datasets
Reviewed by: Christopher Siden <chris.siden@delphix.com>
Approved by: Eric Schrock <Eric.Schrock@delphix.com>

References:
  illumos/illumos-gate@ce636f8b38e8c9ff484e880d9abb27251a882860
  illumos changeset: 13776:cd512c80fd75
  https://www.illumos.org/issues/3086

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Illumos #3349: zpool upgrade -V bumps the on disk version number

3349 zpool upgrade -V bumps the on disk version number, but leaves
the in core version
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <chris.siden@delphix.com>
Reviewed by: Matt Ahrens <matthew.ahrens@delphix.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Approved by: Dan McDonald <danmcd@nexenta.com>

References:
  illumos/illumos-gate@25345e466695fbe736faa53b8f3413d8e8f81981
  https://www.illumos.org/issues/3349

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fix __zio_execute() asynchronous dispatch

To save valuable stack all zio's were made asynchronous when in the
tgx_sync_thread context or during pool initialization.  See commit
2fac4c2 for the original patch and motivation.

Unfortuantely, the changes to dsl_pool_sync_context() made by the
feature flags broke this logic causing in __zio_execute() to dispatch
itself infinitely when called during pool initialization.  This
commit refines the existing logic to specificly target only the two
cases we care about.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Illumos #3104: eliminate empty bpobjs

3104 eliminate empty bpobjs
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <chris.siden@delphix.com>
Reviewed by: Garrett D'Amore <garrett@damore.org>
Approved by: Eric Schrock <eric.schrock@delphix.com>

References:
  illumos/illumos-gate@f17457368189aa911f774c38c1f21875a568bdca
  illumos changeset: 13782:8f78aae28a63
  https://www.illumos.org/issues/3104

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Illumos #3145, #3212

3145 single-copy arc
3212 ztest: race condition between vdev_online() and spa_vdev_remove()

Reviewed by: Matt Ahrens <matthew.ahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Justin T. Gibbs <gibbs@scsiguy.com>
Approved by: Eric Schrock <eric.schrock@delphix.com>

References:
  illumos-gate/commit/9253d63df408bb48584e0b1abfcc24ef2472382e
  illumos changeset: 13840:97fd5cdf328a
  https://www.illumos.org/issues/3145
  https://www.illumos.org/issues/3212

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #989
Closes #1137
Merge branch 'feature-flags'

Feature flags support for ZFS ported from Illumos.  Only minimal
compatibility changes were made where required to accomidate Linux.
For a detailed description of feature flags see original proposal
on zfs-discuss.  They are conceptually very similar to Linux's
ext[234] style of feature flags.

http://lists.freebsd.org/pipermail/freebsd-fs/2011-May/011568.html

NOTE: This branch updates the default pool version for new pools
from 28 to 5000.  Version 28 pools may still be created for
compatibility with Solaris by using the '-o version=28' option.

$ zpool create -o version=28 ...

Existing pools must be manually upgraded using 'zpool upgrade'.

$ zpool upgrade ...

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #778
Only reduce __zio_execute() stack usage in kernel space

Related to 91579709fccd3e55a21970742b66c388fb1403db we need to
be very careful about not overrunning the stack in kernel space.
However, in user space we're already allowing slightly larger
stacks so this stack usage optimization is not required there.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Revert "Avoid ELOOP on auto-mounted snapshots"

This reverts commit 7afcf5b1da83549bfba70a61fae7a00eaa63c2b0 which
accidentally introduced a regression with the .zfs snapshot directory.
While the updated code still does correctly mount the requested
snapshot.  It updates the vfsmount such that it references the
original dataset vfsmount.  The result is that the snapshot itself
isn't visible.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #816
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.

One visible consequence of this change was that processes accessing
automounted snapshots received an ELOOP error because they failed to
wait for zfs.mount to complete.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #816
Report realpath() canonicalization error

Rather than just reporting the failure include the passed
mount point and error number.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1153