Add a unique "eid" value to all zevents

Tagging each zevent with a unique monotonically increasing EID
(Event IDentifier) provides the required infrastructure for a user
space daemon to reliably process zevents.  By writing the EID to
persistent storage the daemon can safely resume where it left off
in the event stream when it's restarted.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Issue #2
Add zpool_events_seek() functionality

The ZFS_IOC_EVENTS_SEEK ioctl was added to allow user space callers
to seek around the zevent file descriptor by EID.  When a specific
EID is passed and it exists the cursor will be positioned there.
If the EID is no longer cached by the kernel ENOENT is returned.
The caller may also pass ZEVENT_SEEK_START or ZEVENT_SEEK_END to seek
to those respective locations.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Issue #2
Clarify zpool_events_next() comment

Due to the very poorly chosen argument name 'cleanup_fd' it was
completely unclear that this file descriptor is used to track the
current cursor location.  When the file descriptor is created by
opening ZFS_DEV a private cursor is created in the kernel for the
returned file descriptor.  Subsequent calls to zpool_events_next()
and zpool_events_seek() then require the file descriptor as an
argument to reposition the cursor.  When the file descriptor is
closed the kernel state tracking the cursor is destroyed.

This patch contains no functional change, it just changes a
few variable names and clarifies the documentation.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Issue #2
Add defs for makefile installation dir vars

Add macro definitions to AM_CPPFLAGS to propagate makefile installation
directory variables for libexecdir, runstatedir, sbindir, and
sysconfdir.

https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Installation-Directory-Variables.html

  A corollary is that you should not use these variables except
  in makefiles. For instance, instead of trying to evaluate
  datadir in configure and hard-coding it in makefiles using e.g.,
  'AC_DEFINE_UNQUOTED([DATADIR], ["$datadir"], [Data directory.])',
  you should add -DDATADIR='$(datadir)' to your makefile's definition
  of CPPFLAGS (AM_CPPFLAGS if you are also using Automake).

The runstatedir directory is for "installing data files which the
programs modify while they run, that pertain to one specific machine,
and which need not persist longer than the execution of the program".

https://www.gnu.org/prep/standards/html_node/Directory-Variables.html

It will be defined by autoconf 2.70 or later, and default to
"$(localstatedir)/run".

http://git.savannah.gnu.org/gitweb/?p=autoconf.git;a=commit;h=a197431414088a417b407b9b20583b2e8f7363bd

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2
Replace zpool_events_next() "block" parm w/ "flags"

zpool_events_next() can be called in blocking mode by specifying a
non-zero value for the "block" parameter.  However, the design of
the ZFS Event Daemon (zed) requires additional functionality from
zpool_events_next().  Instead of adding additional arguments to the
function, it makes more sense to use flags that can be bitwise-or'd
together.

This commit replaces the zpool_events_next() int "block" parameter with
an unsigned bitwise "flags" parameter.  It also defines ZEVENT_NONE
to specify the default behavior.  Since non-blocking mode can be
specified with the existing ZEVENT_NONBLOCK flag, the default behavior
becomes blocking mode.  This, in effect, inverts the previous use
of the "block" parameter.  Existing callers of zpool_events_next()
have been modified to check for the ZEVENT_NONBLOCK flag.

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2
Initial implementation of zed (ZFS Event Daemon)

zed monitors ZFS events.  When a zevent is posted, zed will run any
scripts that have been enabled for the corresponding zevent class.
Multiple scripts may be invoked for a given zevent.  The zevent
nvpairs are passed to the scripts as environment variables.

Events are processed synchronously by the single thread, and there is
no maximum timeout for script execution.  Consequently, a misbehaving
script can delay (or forever block) the processing of subsequent
zevents.  Plans are to address this in future commits.

Initial scripts have been developed to log events to syslog
and send email in response to checksum/data/io errors and
resilver.finish/scrub.finish events.  By default, email will only
be sent if the ZED_EMAIL variable is configured in zed.rc (which is
serving as a config file of sorts until a proper configuration file
is implemented).

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2
Add systemd unit file for zed

This commit adds a systemd unit file for zed.service and integrates
it into the zfs.target from commit 881f45c.

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2108
Issue #2
Make command line guid parsing more tolerant

Several of the zfs utilities allow you to pass a vdev's guid rather
than the device name.  However, the utilities are not consistent in
how they parse that guid.  For example, 'zinject' expects the guid
to be passed as a hex value while 'zpool replace' wants it as a
decimal.  The user is forced to just know what format to use.

This patch improve things by making the parsing more tolerant.
When strtol(3) is called using 0 for the base, rather than say
10 or 16, it will then accept hex, decimal, or octal input based
on the prefix.  From the man page.

    If base is zero or 16, the string may then include a "0x"
    prefix, and  the number  will  be read in base 16; otherwise,
    a zero base is taken as 10 (decimal) unless the next character
    is '0', in which case it  is  taken as 8 (octal).

NOTE: There may be additional conversions not caught be this patch.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Issue #2
Add missing DATA_TYPE_STRING_ARRAY output

This functionality has always been missing.  But until now there
were no zevents which included an array of strings so it wasn't
missed.  However, that's now changed so to ensure this information
is output correctly by 'zpool events -v' the DATA_TYPE_STRING_ARRAY
has been implemented.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Issue #2
Add automatic hot spare functionality

When a vdev starts getting I/O or checksum errors it is now
possible to automatically rebuild to a hot spare device.

To cleanly support this functionality in a shell script some
additional information was added to all zevent ereports which
include a vdev.  This covers both io and checksum zevents but
may be used but other scripts.

In the Illumos FMA solution the same information is required
but it is retrieved through the libzfs library interface.
Specifically the following members were added:

  vdev_spare_paths  - List of vdev paths for all hot spares.
  vdev_spare_guids  - List of vdev guids for all hot spares.
  vdev_read_errors  - Read errors for the problematic vdev
  vdev_write_errors - Write errors for the problematic vdev
  vdev_cksum_errors - Checksum errors for the problematic vdev.

By default the required hot spare scripts are installed but this
functionality is disabled.  To enable hot sparing uncomment the
ZED_SPARE_ON_IO_ERRORS and ZED_SPARE_ON_CHECKSUM_ERRORS in the
/etc/zfs/zed.d/zed.rc configuration file.

These scripts do no add support for the autoexpand property. At
a minimum this requires adding a new udev rule to detect when
a new device is added to the system.  It also requires that the
autoexpand policy be ported from Illumos, see:

  https://github.com/illumos/illumos-gate/blob/master/usr/src/cmd/syseventd/modules/zfs_mod/zfs_mod.c

Support for detecting the correct name of a vdev when it's not
a whole disk was added by Turbo Fredriksson.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Issue #2
Replace check for _POSIX_MEMLOCK w/ HAVE_MLOCKALL

zed supports a '-M' cmdline opt to lock all pages in memory via
mlockall().  The _POSIX_MEMLOCK define is checked to determine whether
this function is supported.  The current test assumes mlockall()
is supported if _POSIX_MEMLOCK is non-zero.  However, this test is
insufficient according to mlock(2) and sysconf(3).  If _POSIX_MEMLOCK
is -1, mlockall() is not supported; but if _POSIX_MEMLOCK is 0,
availability must be checked at runtime.

This commit adds an autoconf check for mlockall() to user.m4.  The zed
code block for mlockall() is now guarded with a test for HAVE_MLOCKALL.
If defined, mlockall() will be called and its runtime availability
checked via its return value.

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2
Merge branch 'zed-initial'

zed monitors ZFS events. When a zevent is posted, zed will run any
scripts that have been enabled for the corresponding zevent class.
Multiple scripts may be invoked for a given zevent. The zevent nvpairs
are passed to the scripts as environment variables. Refer to the zed(8)
manpage for details.

Events are processed synchronously by the single thread, and there is
no maximum timeout for script execution. Consequently, a misbehaving
script can delay (or forever block) the processing of subsequent
zevents. Plans are to address this in future commits.

An EID (Event IDentifier) has been added to each event to uniquely
identify it throughout the lifetime of the loaded ZFS kernel module;
it is a monotonically increasing integer that resets to 1 each time
the module is loaded.

Initial scripts have been developed to log zevents to syslog,
automatically rebuild to a hot spare device, and send email in
response to checksum / data / io / resilver.finish / scrub.finish
zevents. To enable email notifications, configure ZED_EMAIL in zed.rc
(which is serving as a config file of sorts until a proper
configuration file is implemented). To enable hot sparing, uncomment
ZED_SPARE_ON_IO_ERRORS and ZED_SPARE_ON_CHECKSUM_ERRORS in zed.rc;
note that the autoexpand property is not yet supported.

zed is a work-in-progress.

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2
Revert "Fixed a use-after-free bug in zfs_zget()."

This reverts commit 36df284366caa77cb40083d2e6bcce02274e2f05.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fix deadlock in zfs_zget()

zfsonlinux/zfs#180 occurred because of a race between inode eviction and
zfs_zget(). zfsonlinux/zfs@36df284 tried to address it by making a call
to the VFS to learn whether an inode is being evicted.  If it was being
evicted the operation was retried after dropping and reacquiring the
relevant resources.  Unfortunately, this introduced another deadlock.

  INFO: task kworker/u24:6:891 blocked for more than 120 seconds.
        Tainted: P           O 3.13.6 #1
  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  kworker/u24:6   D ffff88107fcd2e80     0   891      2 0x00000000
  Workqueue: writeback bdi_writeback_workfn (flush-zfs-5)
   ffff8810370ff950 0000000000000002 ffff88103853d940 0000000000012e80
   ffff8810370fffd8 0000000000012e80 ffff88103853d940 ffff880f5c8be098
   ffff88107ffb6950 ffff8810370ff980 ffff88103a9a5b78 0000000000000000
  Call Trace:
   [<ffffffff813dd1d4>] schedule+0x24/0x70
   [<ffffffff8115fc09>] __wait_on_freeing_inode+0x99/0xc0
   [<ffffffff8115fdd8>] find_inode_fast+0x78/0xb0
   [<ffffffff811608c5>] ilookup+0x65/0xd0
   [<ffffffffa035c5ab>] zfs_zget+0xdb/0x260 [zfs]
   [<ffffffffa03589d6>] zfs_get_data+0x46/0x340 [zfs]
   [<ffffffffa035fee1>] zil_add_block+0xa31/0xc00 [zfs]
   [<ffffffffa0360642>] zil_commit+0x12/0x20 [zfs]
   [<ffffffffa036a6e4>] zpl_putpage+0x174/0x840 [zfs]
   [<ffffffff811071ec>] do_writepages+0x1c/0x40
   [<ffffffff8116df2b>] __writeback_single_inode+0x3b/0x2b0
   [<ffffffff8116ecf7>] writeback_sb_inodes+0x247/0x420
   [<ffffffff8116f5f3>] wb_writeback+0xe3/0x320
   [<ffffffff81170b8e>] bdi_writeback_workfn+0xfe/0x490
   [<ffffffff8106072c>] process_one_work+0x16c/0x490
   [<ffffffff810613f3>] worker_thread+0x113/0x390
   [<ffffffff81066edf>] kthread+0xdf/0x100

This patch implements the original fix in a slightly different manner in
order to avoid both deadlocks.  Instead of relying on a call to ilookup()
which can block in __wait_on_freeing_inode() the return value from igrab()
is used.  This gives us the information that ilookup() provided without
the risk of a deadlock.

Alternately, this race could be closed by registering an sops->drop_inode()
callback.  The callback would need to detect the active SA hold thereby
informing the VFS that this inode should not be evicted.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #180
Fix locking order in zfs_zget()

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Fix for re-reading /etc/mtab.

This is a continuation of fb5c53ea65b75c67c23f90ebbbb1134a5bb6c140:

    When /etc/mtab is updated on Linux it's done atomically with
    rename(2).  A new mtab is written, the existing mtab is unlinked,
    and the new mtab is renamed to /etc/mtab.  This means that we
    must close the old file and open the new file to get the updated
    contents.  Using rewind(3) will just move the file pointer back
    to the start of the file, freopen(3) will close and open the file.

In this commit, a few more rewind(3) calls were replaced with freopen(3)
to allow updated mtab entries to be picked up immediately.

Signed-off-by: John M. Layman <jml@frijid.net>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2215
Issue #1611
Support using overlay mounts in defaults/init script.

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2103
Allow specifying '-o <opts>' in defaults/init script.

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2103