Use stderr for 'no pools/datasets available' error

The 'zfs list' and 'zpool list' commands output the message
'no datasets/pools available' to stdout.  This should go to
stderr and only the available datasets/pools should go to
stdout.  Returning nothing to stdout is expected behavior
when there is nothing to list.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #581
Add missing NULL in zpl_xattr_handlers

The xattr_resolve_name() helper function expects the registered
list of xattr handlers to be NULL terminated.  This NULL was
accidentally missing which could result in a NULL dereference.

Interestingly this issue only manifested itself on certain 32-bit
systems.  Presumably on 64-bit kernels we just always happen to
get lucky and the memory following the structure is zeroed.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #594
ZFS 0.6.0-rc7
Revert "Add zio constructor/destructor"

This patch was slightly flawed and allowed for zio->io_logical
to potentially not be reinitialized for a new zio.  This could
lead to assertion failures in specific cases when debugging is
enabled (--enable-debug) and I/O errors are encountered.  It
may also have caused problems when issues logical I/Os.

Since we want to make sure this workaround can be easily removed
in the future (when we have the real fix).  I'm reverting this
change and applying a new version of the patch which includes
the zio->io_logical fix.

This reverts commit 2c6d0b1e07b0265f0661ed7851d3aa8d3e75e7a9.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #602
Issue #604
Add zio constructor/destructor

Add a standard zio constructor and destructor.  Normally, this is
done to reduce to cost of allocating a new structure by reducing
expensive operations such as memory allocations.  However, in this
case none of the operations moved out of zio_create() were really
very expensive.

This change was principly made as a debug patch (and workaround)
for a zio_destroy() race.  The is good evidence that zio_create()
is reinitializing a mutex which is really still in use by another
thread.  This would completely explain the observed symptoms in
the issue report.

This patch doesn't fix the root cause of the race, but it should
make it less likely by only initializing the mutex once in the
constructor.  Also, this particular flaw might have gone unnoticed
in other zfs implementations due to the specific implementation
details of Linux ticket spinlocks.

Once the real root cause is determined and resolved this change
can be safely reverted.  Until then this should help workaround
the issue.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #496
Add .zfs control directory

Add support for the .zfs control directory.  This was accomplished
by leveraging as much of the existing ZFS infrastructure as posible
and updating it for Linux as required.  The bulk of the core
functionality is now all there with the following limitations.

*) The .zfs/snapshot directory automount support requires a 2.6.37
   or newer kernel.  The exception is RHEL6.2 which has backported
   the d_automount patches.

*) Creating/destroying/renaming snapshots with mkdir/rmdir/mv
   in the .zfs/snapshot directory works as expected.  However,
   this functionality is only available to root until zfs
   delegations are finished.

      * mkdir - create a snapshot
      * rmdir - destroy a snapshot
      * mv    - rename a snapshot

The following issues are known defeciences, but we expect them to
be addressed by future commits.

*) Add automount support for kernels older the 2.6.37.  This should
   be possible using follow_link() which is what Linux did before.

*) Accessing the .zfs/snapshot directory via NFS is not yet possible.
   The majority of the ground work for this is complete.  However,
   finishing this work will require resolving some lingering
   integration issues with the Linux NFS kernel server.

*) The .zfs/shares directory exists but no futher smb functionality
   has yet been implemented.

Contributions-by: Rohan Puri <rohan.puri15@gmail.com>
Contributiobs-by: Andrew Barnes <barnes333@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #173
Account for .zfs ctldir inodes

Because the .zfs ctldir inodes are not backed by physical storage
they use a different create path which was not properly accounting
for them as used.  This could result in ->nr_cached_objects()
returning 0 and cause a divide by zero error in prune_super().

In my option there's a kernel bug here too which allows this to
happen.  They should either be checking for 0 or adding +1 like
they correctly do earlier in the function.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #617
Add ZFS_META_RELEASE to module load/unload messages

Include the ZFS_META_RELEASE in the module load/unload messages
to more clearly indidcate exactly what version of ZFS has been
loaded.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Enhance a dmu_tx_dirty_buf() assertion

The following assertion is good to validate the correctness of
new DMU consumers, but it doesn't quite provide enough information.
Slightly rework the assertion so that when it is hit the actual
offending values will be included in the output.

  SPLError: 4787:0:(dmu_tx.c:828:dmu_tx_dirty_buf())
  ASSERTION(dn == NULL || dn->dn_assigned_txg == tx->tx_txg) failed

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Add --enable-debug-dmu-tx configure option

Allow rigorous (and expensive) tx validation to be enabled/disabled
indepentantly from the standard zfs debugging.  When enabled these
checks ensure that all txs are constructed properly and that a dbuf
is never dirtied without taking the correct tx hold.

This checking is particularly helpful when adding new dmu consumers
like Lustre.  However, for established consumers such as the zpl
with no known outstanding tx construction problems this is just
overhead.

--enable-debug-dmu-tx  - Enable/disable validation of each tx as
--disable-debug-dmu-tx   it is constructed.  By default validation
                         is disabled due to performance concerns.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fix executable permissions

Caught by lint, this permission change was accidentally introduced
by commit 42cb3819f1a1f536105faac81ffc150f3da90a80.  Restore the
correct permissions and while I'm at it add a missing whack-bang
to config/ltmain.sh.

  lint: executable-not-elf-or-script: zpool_main.c zfs_main.c

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #620
ZFS 0.6.0-rc8
Remove hard-coded 80 column output

When stdout is detected to be a tty use the number of columns
specified by the terminal.  If that fails fall back to a default
80 column width.  In the non-tty case allow for 999 column lines.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Properly expose the mfu ghost list kstats

Due to a typo the mru ghost lists stats were accidentally being
exposed as the mfu ghost list stats.  This was harmless but
confusing since memory usage could be over reported.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Print human readable error message for ENOENT

A cryptic error code is printed when mounting a legacy dataset to a
non-existent mountpoint. This patch changes this behavior to print
"mount point '%s' does not exist", which is similar to the error
message printed when mounting procfs.

The single quotes were added to be consistent with the existing EBUSY
error message, which is the only difference between this error message
and the one that is printed when the same condition occurs when mounting
procfs.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #633
Make Gentoo initscript use modinfo

The -l parameter to modprobe has been removed from the latest upstream
code and this change has entered Gentoo. Using modinfo as a substitute
addresses this.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #636
Fixed a NULL pointer dereference bug in zfs_preumount

When zpl_fill_super -> zfs_domount fails (e.g. because the dataset
was destroyed before it could be successfully mounted) the subsequent
call to zpl_kill_sb -> zfs_preumount would derefence a NULL pointer.

This bug can be reproduced using this shell script:

 #!/bin/sh
 (
 while true; do
 	zfs create -o mountpoint=legacz tank/bar
 	zfs destroy tank/bar
 done
 ) &

 (
 while true; do
 	mount -t zfs tank/bar /mnt
 	umount /mnt
 done
 ) &

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #639
Export additional dsl symbols

Principly these symbols were exported to get access to the
dsl_prop_register/dsl_prop_unregister functions.  They allow
us to cleanly register a callback which is called when a
dataset property is modified.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Document the zle compression algorithm

Signed-off-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Improve error message consistency

Signed-off-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>