Some nvlist allocations in hold processing need to use KM_PUSHPAGE.

This should hopefully catch the rest of the allocations in the
user hold/release processing that were missed by commit
65c67ea86e9f112177f1ad32de8e780f10798a64.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1852
Closes #1855
Drive database update

Added:

Adata S396 (obtained from drive_id)
Apple MacBookAir3,1 SSD (obtained from drive_id)
Apple MacBookPro10,1 SSD (obtained from drive_id)
Intel 510 (obtained from drive_id)
Intel 710 (obtained from drive_id)
Intel DC S3500 (obtained from drive_id)
Netapp LUN (obtained from illumos user's sd.conf)
OCZ Agility 3 (obtained from drive_id)
OCZ Vertex (obtained from drive_id)
Samsung PM800 (obtained from drive_id)
Sandisk U100 (obtained from drive_id)
Sun Comstar (obtained from illumos user's sd.conf)

Notes:

1. The entries for the Intel DC S3500 were extrapolated from the 800GB
model's entry, which is "ATA     INTEL SSDSC2BB80".

2. The entires for the Intel 710 were extrapolated from the 120GG
model's entry, which is "ATA     INTEL SSDSA2BZ12".

3. The entires for the Intel 510 were extrapolated from the 250GB
model's entry, which is "ATA     INTEL SSDSC2MH25".

4. The entires for the Apple MacBookPro10,1 SSD were extrapolated from
the 512GB model's entry, which is "ATA     APPLE SSD SM512E". Google
searches suggest that this is a rebadged Samsung 830.

5. The entires for the Apple MacBookAir3,1 SSD were extrapolated from
the 128GB model's entry, which is "ATA     APPLE SSD TS128C". Google
searches suggest that this is a rebadged Kingston SSDNow V+ 100 (based
on Toshiba).

6. Sun Comstar is an iSCSI Target, so we cannot tell what the correct
sector size is through this method. We list it only for reference
purposes, but it is commented out. Similarly, it is not clear what the
right thing to do for Netapp is, so we comment it out.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1907
Remove incorrect ASSERT in zfs_sb_teardown()

As part of zfs_sb_teardown() there is an assertion that all inodes
which are part of the zsb->z_all_znodes list have at least one
reference on them.  This is always true for the standard unmount
case but there are two other cases where it is not strictly true.

* zfs_ioc_rollback() - This is the most common case and it results
  from the fact that we aren't unmounting the filesystem.  During a
  normal unmount the MS_ACTIVE flag will be cleared on the super block
  causing iput_final() to evict the inode when its reference count
  drops to zero.  However, during a rollback MS_ACTIVE remains set
  since we're rolling back a live filesystem and need to preserve the
  existing super block.  This allows inodes with a zero reference count
  to stay in the cache thereby violating the assertion.

* destroy_inode() / zfs_sb_teardown() - There exists a small race
  between dropping the last reference on an inode and removing it from
  the zsb->z_all_znodes list.  This is unlikely to occur but could also
  trigger the assertion which is incorrect.  The inode may safely have
  a zero reference count in this case.

Since allowing a zero reference count on the inode is expected and
safe for both of these cases the simplest thing to do is remove the
ASSERT.  This code is only enabled for default builds so removing
this entirely is a very safe change.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes #1417
Closes #1536