Use setmntent() OR fopen()

For the same reasons it's used in libzfs_init(), this was just
overlooked because zinject gets minimal use.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1498
No point in rewind() mtab in zfs_unshare_proto(). We're not really
reading the file, but instead use libzfs_mnttab_find() which does
the nessesary freopen() for us.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1498
Don't specifically open /etc/mtab - it is done in libzfs_init()
a few lines further down and we can share the open file handle.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1498
Fix z_wr_iss_h zio_execute() import hang

Because we need to be more frugal about our stack usage under
Linux.  The __zio_execute() function was modified to re-dispatch
zios to a ZIO_TASKQ_ISSUE thread when we're in a context which
is known to be stack heavy.  Those two contexts are the sync
thread and what ever thread is performing spa initialization.

Unfortunately, this change introduced an unlikely bug which can
result in a zio being re-dispatched indefinitely and never being
executed.  If during spa initialization we handle a zio with
ZIO_PRIORITY_NOW it will be moved to the high priority queue.
When __zio_execute() is called again for the zio it will mis-
interpret the context and re-dispatch it again.  The system
will get stuck spinning re-dispatching the zio and making no
forward progress.

To fix this rare issue __zio_execute() has been updated not
to re-dispatch zios on either the ZIO_TASKQ_ISSUE or
ZIO_TASKQ_ISSUE_HIGH task queues.

In practice this issue was rarely reported and can usually
be fixed by rebooting the system and importing the pool again.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1455
Linux 3.11 compat: fops->iterate()

Commit torvalds/linux@2233f31aade393641f0eaed43a71110e629bb900
replaced ->readdir() with ->iterate() in struct file_operations.
All filesystems must now use the new ->iterate method.

To handle this the code was reworked to use the new ->iterate
interface.  Care was taken to keep the majority of changes
confined to the ZPL layer which is already Linux specific.
However, minor changes were required to the common zfs_readdir()
function.

Compatibility with older kernels was accomplished by adding
versions of the trivial dir_emit* helper functions.  Also the
various *_readdir() functions were reworked in to wrappers
which create a dir_context structure to pass to the new
*_iterate() functions.

Unfortunately, the new dir_emit* functions prevent us from
passing a private pointer to the filldir function.  The xattr
directory code leveraged this ability through zfs_readdir()
to generate the list of xattr names.  Since we can no longer
use zfs_readdir() a simplified zpl_xattr_readdir() function
was added to perform the same task.

Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1653
Issue #1591
Implement database to workaround misreported physical sector sizes

This implements vdev_bdev_database_check(). It alters the detected
sector size of any device listed in a database of drives known to lie
about their physical sector sizes.

This is based on "6931570 Add flash devices' VID/PID to disk table to
advertising 4K physical sector size" from Open Solaris and on
sg_simple4.c from sg3_utils. About two dozen lines are taken from
sg_simple4.c, which is GPLv2 licensed. However, sg_simple4.c is
analogous to a Hello World program and is safe for us to use. We
requested that Douglas Gilbert, the author of sg_simple4.c, confirm that
this is the case. A cutdown version of his response is as follows:

```
I would consider a SCSI INQUIRY example using the Linux sg
driver interface (also written by me) as the equivalent of an
"hello world" program in C.
```

The database was created with the help of the freenode and ZFSOnLinux
communities.

Some notes:

1. The following drives both were confirmed to lie via reports in IRC
and they contain capacity information in their identifiers:

INTEL SSDSA2M080
INTEL SSDSA2M160
M4-CT256M4SSD2
WDC WD15EARS-00S
WDC WD15EARS-00Z
WDC WD20EARS-00M

The identifiers for different capacity models were extrapolated and
added under the assumption that those models also lie. Google was used
to verify that the extrapolated drive identifiers existed prior to their
inclusion.

2. The OCZ-VERTEX2 3.5 identifer applies to two drives that differ
solely in page size (and slightly in capacity). One uses 4096-byte pages
and the other uses 8192-byte pages. Both are set to use 8192-byte pages.
We could detect the page size by checking the capacity, but that would
unnecessarily complicate the code.

3. It is possible for updated drive firmware to correctly report the
sector size. There were reports of a few advanced format drives doing
that. One report stated that the vendor changed the identification
string while another was unclear on this. Both reports involved WDC
models.

4. Google was used to determine the size of pages in the listed flash
devices. Reports of 8192-byte pages took precedence over reports of
4096-byte pages.

5. Devices behind USB adapters can have their identification strings
altered. Identification strings obtained across USB adapters are
omitted and no attempt is made to correct for alterations made by USB
adapters when doing comparisons against the database. Two entries in the
Open Solaris database that appear to have been altered by a USB
adapter were omitted.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1652
Revert "Evict meta data from ghost lists + l2arc headers"

This reverts commit fadd0c4da1e2ccd6014800d8b1a0fd117dd323e8 which
introduced a regression in honoring the meta limit.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Close #1660
Use directory xattrs for symlinks

There is currently a subtle bug in the SA implementation which
can crop up which prevents us from safely using multiple variable
length SAs in one object.

Fortunately, the only existing use case for this are symlinks with
SA based xattrs.  Therefore, until the root cause in the SA code
can be identified and fixed we prevent adding SA xattrs to symlinks.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1468
Tag zfs-0.6.2

META file and release log updated.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Merge branch 'nagios' of github.com:DeHackEd/zfs into nagios