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Brian Behlendorf 278bee9319 Linux 3.18 compat: Snapshot auto-mounting
Re-factor the .zfs/snapshot auto-mouting code to take in to account
changes made to the upstream kernels.  And to lay the groundwork for
enabling access to .zfs snapshots via NFS clients.  This patch makes
the following core improvements.

* All actively auto-mounted snapshots are now tracked in two global
trees which are indexed by snapshot name and objset id respectively.
This allows for fast lookups of any auto-mounted snapshot regardless
without needing access to the parent dataset.

* Snapshot entries are added to the tree in zfsctl_snapshot_mount().
However, they are now removed from the tree in the context of the
unmount process.  This eliminates the need complicated error logic
in zfsctl_snapshot_unmount() to handle unmount failures.

* References are now taken on the snapshot entries in the tree to
ensure they always remain valid while a task is outstanding.

* The MNT_SHRINKABLE flag is set on the snapshot vfsmount_t right
after the auto-mount succeeds.  This allows to kernel to unmount
idle auto-mounted snapshots if needed removing the need for the
zfsctl_unmount_snapshots() function.

* Snapshots in active use will not be automatically unmounted.  As
long as at least one dentry is revalidated every zfs_expire_snapshot/2
seconds the auto-unmount expiration timer will be extended.

* Commit torvalds/linux@bafc9b7 caused snapshots auto-mounted by ZFS
to be immediately unmounted when the dentry was revalidated.  This
was a consequence of ZFS invaliding all snapdir dentries to ensure that
negative dentries didn't mask new snapshots.  This patch modifies the
behavior such that only negative dentries are invalidated.  This solves
the issue and may result in a performance improvement.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3589
Closes #3344
Closes #3295
Closes #3257
Closes #3243
Closes #3030
Closes #2841
2015-08-31 13:54:39 -07:00
cmd Add extra keyword 'slot' to vdev_id.conf 2015-08-30 10:03:56 -07:00
config Linux 3.18 compat: Snapshot auto-mounting 2015-08-31 13:54:39 -07:00
contrib Make sure that POOL_IMPORTED is set, unset and checked where appropriate. 2015-07-28 13:29:28 -07:00
etc Some OpenRC dependency logic belongs in mount 2015-08-30 10:06:59 -07:00
include Linux 3.18 compat: Snapshot auto-mounting 2015-08-31 13:54:39 -07:00
lib Check large block feature flag on volumes 2015-08-28 09:25:03 -07:00
man Add extra keyword 'slot' to vdev_id.conf 2015-08-30 10:03:56 -07:00
module Linux 3.18 compat: Snapshot auto-mounting 2015-08-31 13:54:39 -07:00
rpm Set default _initconfdir directory 2015-07-21 13:16:50 -07:00
scripts Use truncate instead of fallocate in ziltest.sh 2015-07-13 11:02:59 -07:00
udev Support parallel build trees (VPATH builds) 2015-07-17 13:42:51 -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
autogen.sh build: do not call boilerplate ourself 2013-04-02 10:55:20 -07:00
configure.ac Move dracut directory to contrib 2015-07-09 13:59:37 -07:00
copy-builtin Consistent menuconfig name 2012-08-26 13:49:37 -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
Makefile.am Support parallel build trees (VPATH builds) 2015-07-17 13:42:51 -07:00
META Tag zfs-0.6.4 2015-04-08 20:16:45 -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
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

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