This topic branch leverages the Solaris style FMA call points
in ZFS to create a user space visible event notification system
under Linux. This new system is called zevent and it unifies
all previous Solaris style ereports and sysevent notifications.
Under this Linux specific scheme when a sysevent or ereport event
occurs an nvlist describing the event is created which looks almost
exactly like a Solaris ereport. These events are queued up in the
kernel when they occur and conditionally logged to the console.
It is then up to a user space application to consume the events
and do whatever it likes with them.
To make this possible the existing /dev/zfs ABI has been extended
with two new ioctls which behave as follows.
* ZFS_IOC_EVENTS_NEXT
Get the next pending event. The kernel will keep track of the last
event consumed by the file descriptor and provide the next one if
available. If no new events are available the ioctl() will block
waiting for the next event. This ioctl may also be called in a
non-blocking mode by setting zc.zc_guid = ZEVENT_NONBLOCK. In the
non-blocking case if no events are available ENOENT will be returned.
It is possible that ESHUTDOWN will be returned if the ioctl() is
called while module unloading is in progress. And finally ENOMEM
may occur if the provided nvlist buffer is not large enough to
contain the entire event.
* ZFS_IOC_EVENTS_CLEAR
Clear are events queued by the kernel. The kernel will keep a fairly
large number of recent events queued, use this ioctl to clear the
in kernel list. This will effect all user space processes consuming
events.
The zpool command has been extended to use this events ABI with the
'events' subcommand. You may run 'zpool events -v' to output a
verbose log of all recent events. This is very similar to the
Solaris 'fmdump -ev' command with the key difference being it also
includes what would be considered sysevents under Solaris. You
may also run in follow mode with the '-f' option. To clear the
in kernel event queue use the '-c' option.
$ sudo cmd/zpool/zpool events -fv
TIME CLASS
May 13 2010 16:31:15.777711000 ereport.fs.zfs.config.sync
class = "ereport.fs.zfs.config.sync"
ena = 0x40982b7897700001
detector = (embedded nvlist)
version = 0x0
scheme = "zfs"
pool = 0xed976600de75dfa6
(end detector)
time = 0x4bec8bc3 0x2e5aed98
pool = "zpios"
pool_guid = 0xed976600de75dfa6
pool_context = 0x0
While the 'zpool events' command is handy for interactive debugging
it is not expected to be the primary consumer of zevents. This ABI
was primarily added to facilitate the addition of a user space
monitoring daemon. This daemon would consume all events posted by
the kernel and based on the type of event perform an action. For
most events simply forwarding them on to syslog is likely enough.
But this interface also cleanly allows for more sophisticated
actions to be taken such as generating an email for a failed drive
While I completely agree the udev is the lesser of many possibles
evils when solving the device issue... it is still evil. After
attempting to craft a single rule which will work for various
versions of udev in various distros. I've come to the conclusion
the only maintainable way to solve this issue is to split the rule
from any particular configuration.
This commit provides a generic 60-zpool.rules file which use a
small helper util 'zpool_id' to parse a configuration file by
default located in /etc/zfs/zdev.conf. The helper script maps
a by-path udev name to a more friendly name of <channel><rank>
for large configurations.
As part of this change all of the support scripts why rely on
this udev naming convention have been updated as needed. Example
zdev.conf files have also been added for 3 different systems by
you will always need to add one for your exact hardware.
Finally, included in these changes are the proper tweaks to the
build system to ensure everything still get's packaged properly
in the rpms and can run in or out of tree.
This include updating all the Makefile.am to have the correct
include paths and libraries. In addition, the zlib m4 macro was
updated to more correctly integrate with the Makefiles. And I
added two new macros libblkid and libuuid which will be needed by
subsequent commits for blkid and uuid support respectively. The
blkid support is optional, the uuid support is mandatory for libefi.
Under FC11 rpm builds by default add the --fortify-source option which
ensures that functions flagged with certain attributes must have their
return codes checked. Normally this is just a warning but we always
build with -Werror so this is fatal. Simply wrap the function in a
verify call to ensure we catch a failure if there is one.
Brian Behlendorf