mirror_zfs/include
Serapheim Dimitropoulos 8d103d8856 OpenZFS 8604 - Simplify snapshots unmounting code
Authored by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Andy Stormont <astormont@racktopsystems.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Ported-by: Don Brady <don.brady@delphix.com>

Every time we want to unmount a snapshot (happens during snapshot
deletion or renaming) we unnecessarily iterate through all the
mountpoints in the VFS layer (see zfs_get_vfs).

The current patch completely gets rid of that code and changes
the approach while keeping the behavior of that code path the
same. Specifically, it puts a hold on the dataset/snapshot and
gets its vfs resource reference directly, instead of linearly
searching for it. If that reference exists we attempt to amount
it.

With the above change, it became obvious that the nvlist
manipulations that we do (add_boolean and add_nvlist) take a
significant amount of time ensuring uniqueness of every new
element even though they don't have too. Thus, we updated the
patch so those nvlists are not trying to enforce the uniqueness
of their elements.

A more complete analysis of the problem solved by this patch
can be found below:
https://sdimitro.github.io/post/snap-unmount-perf/

OpenZFS-issue: https://www.illumos.org/issues/8604
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/126118fb
2018-02-08 15:29:44 -08:00
..
linux Linux 3.14 compat: IO acct, global_page_state, etc 2017-09-16 11:00:19 -07:00
sys OpenZFS 8604 - Simplify snapshots unmounting code 2018-02-08 15:29:44 -08:00
libnvpair.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
libuutil_common.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
libuutil_impl.h Support custom build directories and move includes 2010-09-08 12:38:56 -07:00
libuutil.h Correct cppcheck errors 2017-09-19 12:17:29 -07:00
libzfs_core.h OpenZFS 7431 - ZFS Channel Programs 2018-02-08 15:28:18 -08:00
libzfs_impl.h OpenZFS 7431 - ZFS Channel Programs 2018-02-08 15:28:18 -08:00
libzfs.h Added no_scrub_restart flag to zpool reopen 2017-10-26 12:26:09 -07:00
Makefile.am Retire legacy test infrastructure 2017-08-15 17:26:38 -07:00
thread_pool.h Add libtpool (thread pools) 2017-08-09 15:31:08 -07:00
zfeature_common.h Native Encryption for ZFS on Linux 2017-08-14 10:36:48 -07:00
zfs_comutil.h Illumos #2882, #2883, #2900 2013-09-04 15:49:00 -07:00
zfs_deleg.h Native Encryption for ZFS on Linux 2017-08-14 10:36:48 -07:00
zfs_fletcher.h DLPX-44812 integrate EP-220 large memory scalability 2016-11-29 14:34:27 -08:00
zfs_namecheck.h OpenZFS 7386 - zfs get does not work properly with bookmarks 2017-01-26 14:42:15 -08:00
zfs_prop.h Native Encryption for ZFS on Linux 2017-08-14 10:36:48 -07:00