Add zfs_autoimport_disable tunable

There are times when it is desirable for zfs to not automatically
populate the spa namespace at module load time using the pools
in the /etc/zfs/zpool.cache file.  The zfs_autoimport_disable
module option has been added to control this behavior.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #330
Fix the comment in zfs.h

The path to code is also changed in zfsonlinux.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issues #1566
Update zio.c

The cv_wait_io is used to account io time instead of cv_wait.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1566
Improve code in arc_buf_remove_ref

When we remove references of arc bufs in the arc_anon state we
needn't take its header's hash_lock, so postpone it to where we
really need it to avoid unnecessary invocations of function buf_hash.

Signed-off-by: Ying Zhu <casualfisher@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1557
Avoid abort() in vn_rdwr(): libzpool/kernel.c

Make sure that buffer is aligned to 512 bytes on linux so that
pread call combined with O_DIRECT does not return EINVAL.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1570
zdb: enhancement - Display SA xattrs.

If the znode has SA xattrs, display them following the other
standard attributes.  The format used is similar to that used
when listing the contents of a ZAP.  It is as follows:

	$ zdb -vvv <pool>/<dataset> <object>
	...
	SA xattrs: <size> bytes, <number> entries
		<name1> = <value1>
		<name2> = <value2>
		...

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1581
Readd zpool_clear_label() from OpenSolaris

This patch restores the zpool_clear_label() function from
OpenSolaris.  This was removed by commit d603ed6 because
it wasn't clear we had a use for it in ZoL.  However, this
functionality is a prerequisite for adding the 'zpool labelclear'
command from FreeBSD.

As part of bringing this change in the zpool_clear_label()
function was changed to use fstat64_blk(2) for compatibility
with Linux.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1126
Add FreeBSD 'zpool labelclear' command

The FreeBSD implementation of zfs adds the 'zpool labelclear'
command.  Since this functionality is helpful and straight
forward to add it is being included in ZoL.

References:
  freebsd/freebsd@119a041dc9230275239a8de68c534c0754181e7e

Ported-by: Dmitry Khasanov <pik4ez@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1126
Fix zpool_read_label()

The zpool_read_label() function was subtly broken due to a
difference of behavior in fstat64(2) on Solaris vs Linux.

Under Solaris when a block device is stat'ed the st_size
field will contain the size of the device in bytes.  Under
Linux this is only true for regular file and symlinks.  A
compatibility function called fstat64_blk(2) was added
which can be used when the Solaris behavior is required.

This flaw was never noticed because the only time we would
need to use the device size is when the first two labels
are damaged.  I noticed this issue while adding the
zpool_clear_label() function which is similar in design
and does require us to write all the labels.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Use GFP_NOIO in vdev_disk_io_flush()

To avoid a potential deadlock when using a zvol as a swap
device prevent vdev_disk_io_flush() from performing IO during
the bio_alloc().

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1508
Log pool suspension warnings to the console

In the event that a pool gets suspended log this information to
the console.  This is critical information and we want to make
sure it gets logged.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1555
Add new kstat for monitoring time in dmu_tx_assign

This change adds a new kstat to gain some visibility into the amount of
time spent in each call to dmu_tx_assign. A histogram is exported via
a new dmu_tx_assign_histogram-$POOLNAME file. The information contained
in this histogram is the frequency dmu_tx_assign took to complete given
an interval range. For example, given the below histogram file:

    $ cat /proc/spl/kstat/zfs/dmu_tx_assign_histogram-tank
    12 1 0x01 32 1536 19792068076691 20516481514522
    name                            type data
    1 us                            4    859
    2 us                            4    252
    4 us                            4    171
    8 us                            4    2
    16 us                           4    0
    32 us                           4    2
    64 us                           4    0
    128 us                          4    0
    256 us                          4    0
    512 us                          4    0
    1024 us                         4    0
    2048 us                         4    0
    4096 us                         4    0
    8192 us                         4    0
    16384 us                        4    0
    32768 us                        4    1
    65536 us                        4    1
    131072 us                       4    1
    262144 us                       4    4
    524288 us                       4    0
    1048576 us                      4    0
    2097152 us                      4    0
    4194304 us                      4    0
    8388608 us                      4    0
    16777216 us                     4    0
    33554432 us                     4    0
    67108864 us                     4    0
    134217728 us                    4    0
    268435456 us                    4    0
    536870912 us                    4    0
    1073741824 us                   4    0
    2147483648 us                   4    0

one can see most calls to dmu_tx_assign completed in 32us or less, but a
few outliers did not. Specifically, 4 of the calls took between 262144us
and 131072us. This information is difficult, if not impossible, to gather
without this change.

Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1584
Improve N-way mirror performance

The read bandwidth of an N-way mirror can by increased by 50%,
and the IOPs by 10%, by more carefully selecting the preferred
leaf vdev.

The existing algorthm selects a perferred leaf vdev based on
offset of the zio request modulo the number of members in the
mirror.  It assumes the drives are of equal performance and
that spreading the requests randomly over both drives will be
sufficient to saturate them.  In practice this results in the
leaf vdevs being under utilized.

Utilization can be improved by preferentially selecting the leaf
vdev with the least pending IO.  This prevents leaf vdevs from
being starved and compensates for performance differences between
disks in the mirror.  Faster vdevs will be sent more work and
the mirror performance will not be limitted by the slowest drive.

In the common case where all the pending queues are full and there
is no single least busy leaf vdev a batching stratagy is employed.
Of the N least busy vdevs one is selected with equal probability
to be the preferred vdev for T microseconds.  Compared to randomly
selecting a vdev to break the tie batching the requests greatly
improves the odds of merging the requests in the Linux elevator.

The testing results show a significant performance improvement
for all four workloads tested.  The workloads were generated
using the fio benchmark and are as follows.

1) 1MB sequential reads from 16 threads to 16 files (MB/s).
2) 4KB sequential reads from 16 threads to 16 files (MB/s).
3) 1MB random reads from 16 threads to 16 files (IOP/s).
4) 4KB random reads from 16 threads to 16 files (IOP/s).

               | Pristine              |  With 1461             |
               | Sequential  Random    |  Sequential  Random    |
               | 1MB  4KB    1MB  4KB  |  1MB  4KB    1MB  4KB  |
               | MB/s MB/s   IO/s IO/s |  MB/s MB/s   IO/s IO/s |
---------------+-----------------------+------------------------+
2 Striped      | 226  243     11  304  |  222  255     11  299  |
2 2-Way Mirror | 302  324     16  534  |  433  448     23  571  |
2 3-Way Mirror | 429  458     24  714  |  648  648     41  808  |
2 4-Way Mirror | 562  601     36  849  |  816  828     82  926  |

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1461
Add dkms_version conditional

By adding a dkms_version conditional it's now possible to specify
an exact version of dkms.   This is used by the Fedora and EPEL
yum repositories to ensure the patched version of dkms provided
by the repository is installed.  The patched version of dkms
ensures that the spl modules are built before the zfs modules.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1466
Fix zfsctl_expire_snapshot() deadlock

It is possible for an automounted snapshot which is expiring to
deadlock with a manual unmount of the snapshot.  This can occur
because taskq_cancel_id() will block if the task is currently
executing until it completes.  But it will never complete because
zfsctl_unmount_snapshot() is holding the zsb->z_ctldir_lock which
zfsctl_expire_snapshot() must acquire.

---------------------- z_unmount/0:2153 ---------------------
  mutex_lock                <blocking on zsb->z_ctldir_lock>
  zfsctl_unmount_snapshot
  zfsctl_expire_snapshot
  taskq_thread

------------------------- zfs:10690 -------------------------
  taskq_wait_id             <waiting for z_unmount to exit>
  taskq_cancel_id
  __zfsctl_unmount_snapshot
  zfsctl_unmount_snapshot   <takes zsb->z_ctldir_lock>
  zfs_unmount_snap
  zfs_ioc_destroy_snaps_nvl
  zfsdev_ioctl
  do_vfs_ioctl

We resolve the deadlock by dropping the zsb->z_ctldir_lock before
calling __zfsctl_unmount_snapshot().  The lock is only there to
prevent concurrent modification to the zsb->z_ctldir_snaps AVL
tree.  Moreover, we're careful to remove the zfs_snapentry_t from
the AVL tree before dropping the lock which ensures no other tasks
can find it.  On failure it's added back to the tree.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Closes #1527
Fix read-only pool hang on unmount

During mount a filesystem dataset would have the MS_RDONLY bit
incorrectly cleared even if the entire pool was read-only.
There is existing to code to handle this case but it was being run
before the property callbacks were registered.  To resolve the
issue we move this read-only code after the callback registration.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1338
Fix arc_adapt() spinning in iterate_supers_type()

The iterate_supers_type() function which was introduced in the
3.0 kernel was supposed to provide a safe way to call an arbitrary
function on all super blocks of a specific type.  Unfortunately,
because a list_head was used a bug was introduced which made it
possible for iterate_supers_type() to get stuck spinning on a
super block which was just deactivated.

This can occur because when the list head is removed from the
fs_supers list it is reinitialized to point to itself.  If the
iterate_supers_type() function happened to be processing the
removed list_head it will get stuck spinning on that list_head.

The bug was fixed in the 3.3 kernel by converting the list_head
to an hlist_node.  However, to resolve the issue for existing
3.0 - 3.2 kernels we detect when a list_head is used.  Then to
prevent the spinning from occurring the .next pointer is set to
the fs_supers list_head which ensures the iterate_supers_type()
function will always terminate.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1045
Closes #861
Closes #790
Add documentation for -T and interval to "zpool list"

zpool list has the same options for repeating as zpool iostat
has, but that is not documented. This patch adds the documentation.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Add missing -v to usage help for zpool list.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fix 'zpool list -H' error code

Due to an uninitialized variable it was possible for the command
'zpool list -H' to return a non-zero error when there are no pools.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1605