While module loading itself is synchronous the creation of the /dev/zfs
device is not. This is because /dev/zfs is typically created by a udev
rule after the module is registered and presented to user space through
sysfs. This small window between module loading and device creation
can result in spurious failures of libzfs_init().
This patch closes that race by extending libzfs_init() so it can detect
that the modules are loaded and only if required wait for the /dev/zfs
device to be created. This allows scripts to reliably use the following
shell construct without the need for additional error handling.
$ /sbin/modprobe zfs && /sbin/zpool import -a
To minimize the potential time waiting in libzfs_init() a strategy
similar to adaptive mutexes is employed. The function will busy-wait
for up to 10ms based on the expectation that the modules were just
loaded and therefore the /dev/zfs will be created imminently. If it
takes longer than this it will fall back to polling for up to 10 seconds.
This behavior can be customized to some degree by setting the following
new environment variables. This functionality is provided for backwards
compatibility with existing scripts which depend on the module auto-load
behavior. By default module auto-loading is now disabled.
* ZFS_MODULE_LOADING="YES|yes|ON|on" - Attempt to load modules.
* ZFS_MODULE_TIMEOUT="<seconds>" - Seconds to wait for /dev/zfs
The zfs-import-* systemd service files have been updated to call
'/sbin/modprobe zfs' so they no longer rely on the legacy auto-loading
behavior.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Closes#2556
The zfs-import-cache.service and zfs-import-scan.service should
should be started after cryptsetup to ensure all LUKS devices have
been opened.
Signed-off-by: alteriks <alteriks@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1474
This adds systemd unit files replacing the functionality offered by
the SysV init script found in etc/init.d.
It has been developed and tested on Fedora 19, Fedora 20
and openSuSE 13.1.
Four unit files and one target are offered.
zfs-import-cache.service:
Import pools from /etc/zfs/zpool.cache. This unit will wait for
udev to settle.
zfs-import-scan.service:
Import pools by scanning /dev/disk/by-id for zvols. This unit will
only run if /etc/zfs/zpool.cache is not present. This unit will wait
for udev to settle
zfs-mount.service:
Mount ZFS native filesystems. It contains a dependency to be loaded
before local-fs.target.
zfs-share.service:
Share NFS/SMB filesystems. This unit contains a dependency that
will cause it to be restarted whenever the smb or nfs-server unit
is restarted, restoring the shares added.
zfs.target:
This target pulls in the other units in order to start ZFS. It's
the only unit that can be enabled/disabled, all other services
are static and pulled in by dependencies. It will honour zfs=off
and zfs=no options on the kernel command line.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#2108
