OpenZFS on Linux and FreeBSD
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Brian Behlendorf 87abfcba22 Wait in libzfs_init() for the /dev/zfs device
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
2015-05-22 13:31:58 -07:00
cmd Illumos 5243 - zdb -b could be much faster 2015-05-15 11:14:54 -07:00
config The mount helper mount.zfs MUST be in /sbin (not '$sbindir'). 2015-05-18 16:54:36 -07:00
contrib Add bash completions by Aneurin Price. 2014-08-06 15:03:28 -07:00
dracut Execute udevadm settle before trying to import pools 2015-03-24 13:38:55 -07:00
etc Wait in libzfs_init() for the /dev/zfs device 2015-05-22 13:31:58 -07:00
include Initialize dbu_tqent in dmu_buf_init_user() 2015-05-18 11:39:14 -07:00
lib Wait in libzfs_init() for the /dev/zfs device 2015-05-22 13:31:58 -07:00
man Zdb should be able to open the root dataset 2015-05-15 10:52:46 -07:00
module Illumos 5243 - zdb -b could be much faster 2015-05-15 11:14:54 -07:00
rpm Tag zfs-0.6.4 2015-04-08 20:16:45 -07:00
scripts Set zfs_autoimport_disable default value to 1 2015-02-17 16:09:41 -08:00
udev Open pools asynchronously after module load 2013-07-03 09:24:38 -07:00
.gitignore Ignore *.{deb,rpm,tar.gz} files in the top directory. 2013-04-24 16:18:59 -07:00
.gitmodules Add zimport.sh compatibility test script 2014-02-21 12:10:31 -08:00
AUTHORS Add a missing > to AUTHORS 2014-09-02 14:18:53 -07:00
COPYRIGHT Update ZED copyright boilerplate 2015-05-11 15:07:00 -07:00
DISCLAIMER Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
META Tag zfs-0.6.4 2015-04-08 20:16:45 -07:00
Makefile.am Style check shell scripts 2015-05-20 14:10:03 -07:00
OPENSOLARIS.LICENSE Add CDDL license file 2008-12-01 14:49:34 -08:00
README.markdown Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
autogen.sh build: do not call boilerplate ourself 2013-04-02 10:55:20 -07:00
configure.ac Add RHEL style kmod packages 2015-03-27 14:41:48 -07:00
copy-builtin Consistent menuconfig name 2012-08-26 13:49:37 -07:00
zfs-script-config.sh.in Initial implementation of zed (ZFS Event Daemon) 2014-04-02 13:10:03 -07:00
zfs.release.in Move zfs.release generation to configure step 2012-07-12 12:22:51 -07:00

README.markdown

Native ZFS for Linux!

ZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the Illumos community.

ZFS on Linux, which is also known as ZoL, is currently feature complete. It includes fully functional and stable SPA, DMU, ZVOL, and ZPL layers.

Full documentation for installing ZoL on your favorite Linux distribution can be found at: http://zfsonlinux.org