3.10 API change: block_device_operations->release() returns void

Linux kernel commit torvalds/linux@db2a144 changed the return type
of block_device_operations->release() to void.  Detect the expected
prototype and defined our callout accordingly.

Signed-off-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1494
Explicitly flush output at end of each zevent

For "zpool events -f" flush stdout to ensure the last zevent
is always printed immediately.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1568
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