Use a dedicated taskq for vdev_file

Originally, vdev_file used system_taskq. This would cause a deadlock,
especially on system with few CPUs. The reason is that the prefetcher
threads, which are on system_taskq, will sometimes be blocked waiting
for I/O to finish. If the prefetcher threads consume all the tasks in
system_taskq, the I/O cannot be served and thus results in a deadlock.

We fix this by creating a dedicated vdev_file_taskq for vdev_file I/O.

Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2270
Handle ZPOOL_STATUS_HOSTID_MISMATCH in zpool status

Verbatim imports can cause hostid mismatches, but things otherwise work. `zpool
status` does not handle this and will fail when assertions are enabled:

```
zpool: ../../cmd/zpool/zpool_main.c:4418: status_callback: Assertion `reason == ZPOOL_STATUS_OK' failed.

Program received signal SIGABRT, Aborted.
```

Lets instead add a case to display an informative message such as this:

```
  pool: rpool
 state: ONLINE
status: Mismatch between pool hostid and system hostid on imported pool.
        This pool was previously imported into a system with a different hostid,
        and then was verbatim imported into this system.
action: Export this pool on all systems on which it is imported.
        Then import it to correct the mismatch.
   see: http://zfsonlinux.org/msg/ZFS-8000-EY
  scan: scrub repaired 0 in 0h8m with 0 errors on Thu Apr 17 19:43:57 2014
config:

        NAME        STATE     READ WRITE CKSUM
        rpool       ONLINE       0     0     0
          sda       ONLINE       0     0     0

errors: No known data errors
```

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2342
Allow for lock-free reading zfsdev_state_list.

Restructure the zfsdev_state_list to allow for lock-free reading by
converting to a simple singly-linked list from which items are never
deleted and over which only forward iterations are performed.  It depends
on, among other things, the atomicity of accessing the zs_minor integer
and zs_next pointer.

This fixes a lock inversion in which the zfsdev_state_lock is used by
both the sync task (txg_sync) and indirectly by any user program which
uses /dev/zfs; the zfsdev_release method uses the same lock and then
blocks on the sync task.

The most typical failure scenerio occurs when the sync task is cleaning
up a user hold while various concurrent "zfs" commands are in progress.

Neither Illumos nor Solaris are affected by this issue because they use
DDI interface which provides lock-free reading of device state via the
ddi_get_soft_state() function.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2301
Calculate header size correctly in sa_find_sizes()

In the case where a variable-sized SA overlaps the spill block pointer and
a new variable-sized SA is being added, the header size was improperly
calculated to include the to-be-moved SA.  This problem could be
reproduced when xattr=sa enabled as follows:

	ln -s $(perl -e 'print "x" x 120') blah
	setfattr -n security.selinux -v blahblah -h blah

The symlink is large enough to interfere with the spill block pointer and
has a typical SA registration as follows (shown in modified "zdb -dddd"
<SA attr layout obj> format):

	[ ... ZPL_DACL_COUNT ZPL_DACL_ACES ZPL_SYMLINK ]

Adding the SA xattr will attempt to extend the registration to:

	[ ... ZPL_DACL_COUNT ZPL_DACL_ACES ZPL_SYMLINK ZPL_DXATTR ]

but since the ZPL_SYMLINK SA interferes with the spill block pointer, it
must also be moved to the spill block which will have a registration of:

	[ ZPL_SYMLINK ZPL_DXATTR ]

This commit updates extra_hdrsize when this condition occurs, allowing
hdrsize to be subsequently decreased appropriately.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Issue #2214
Issue #2228
Issue #2316
Issue #2343
Honor zfs_nocacheflush for file vdevs

For consistency with disk vdevs honor the zfs_nocacheflush tunable.
This setting is available primarily for debugging and performance
analysis.

Signed-off-by: HC <mmttdebbcc@yahoo.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2336
Added INTEL SSD 530 Series

INTEL SSD 530 Series... SSDSC2BW24

Signed-off-by: John Albietz <inthecloud247@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2184
This is iSCSI sharing for ZoL (shareiscsi).
* Supports the following iSCSI implementations (in this order of discovery):
  + IET		http://iscsitarget.sourceforge.net
  + STGT	http://stgt.berlios.de
    + Not complete - works in simple tests but better/more testing is needed.
  + SCST	http://scst.sourceforge.net
    + Requires that SCST was compiled with /sys support (the default).
* Will refuse to unshares an active target (one with sessions).
* Supports the following options to the 'shareiscsi' property:
  + name/iqn	Full iSCSI Qualified Name (IQN), including identifier.
		This is generated by iscsi_generate_target():
		+ Uses the content of an optional /etc/iscsi_target_id file:
		  Example: iqn.YYYY-MM.tld.domain
		+ If this file doesn't exist, it uses todays year, month and
		  domain name to generate the iqn.
		+ The dataset name is appended at the end of the iqn, with
		  slashes replaced with dots.
		  => <iqn>:<dataset>
  + lun		LUN (0-16384)
		Default: 0 (1 for STGT)
  + type	Share mode (fileio, blockio, nullio, disk, tape)
		STGT: ssc, pt
		Default: blockio (disk for STGT)
  + iomode	IO mode (wb, wt, ro)
		STGT: rdwr, aio, mmap, sg, ssc
		Default: wt (rdwr for STGT)
  + blocksize	Logical block size (512, 1024, 2048, 4096)
		Default: Volume blocksize, 4096 if not usable.
		NOTE: Currently not supported for STGT (doesn't seem to be
		      an option for it in tgtadm).
* If not called with a 'name/iqn' value, then force setting it.
  This so that the IQN doesn't change every month (when it is
  regenerated again). It will be generated by iscsi_generate_target()
  (see above).

NOTE:
+ Moved nfs.c:foreach_nfs_shareopt() to libshare.c:foreach_shareopt()
  so that it can be (re)used in smb.c and iscsi.c.
+ Use the list_{create,insert}() etc for keeping tabs of the linked lists
  instead of using a home-made version.
+ A half second delay had to be added in lib/libzfs/libzfs_mount.c:zfs_unmount()
  after the successful unshare. This to avoid 'dataset busy' when destroying
  recursivly.
Misc iSCSI fixes/cleanups/attempts to get 'zfs rename' to work.

!! Doesn't - a 'zfs rename' works, but most often than not, the rename
!! IOCTL hangs. Not every time and not always on the first dataset being
!! renamed... Seems a little to random to me.