Commit Graph

8747 Commits

Author SHA1 Message Date
Brian Behlendorf
e1310afae3 Remove get_vmalloc_info() wrapper
The get_vmalloc_info() function was used to back the vmem_size()
function.  This was always problematic and resulted in brittle
code because the kernel never provided a clean interface for
modules.

However, it turns out that the only caller of this function in
ZFS uses it to determine the total virtual address space size.
This can be determined easily without get_vmalloc_info() so
vmem_size() has been updated to take this approach which allows
us to shed the get_vmalloc_info() dependency.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:51 -07:00
Brian Behlendorf
50e41ab1e1 Remove on_each_cpu() wrapper
The on_each_cpu() function has been available since Linux 2.6.27.
There is no longer a need to maintain this compatibility code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:51 -07:00
Brian Behlendorf
b652d169b0 Remove mutex_lock_nested() wrapper
The mutex_lock_nested() function has been available since Linux 2.6.18.
There is no longer a need to maintain this compatibility code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:51 -07:00
Brian Behlendorf
2bc5666f53 Remove i_mutex() configure check
The inode structure has used i_mutex as its internal locking
primitive since 2.6.16.  The compatibility code to check for
the previous semaphore primitive has been removed.  However,
the wrapper function itself is being kept because it's entirely
possible this primitive will change again to allow finer grained
locking.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:51 -07:00
Brian Behlendorf
9f36cace41 Remove kmalloc_node() compatibility code
The kmalloc_node() function has been available since Linux 2.6.12.
There is no longer a need to maintain this compatibility code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:51 -07:00
Brian Behlendorf
d227e114ed Remove linux/uaccess.h header check
The uaccess header has been available in the same location since
Linux 2.6.18.  There is no longer a need to maintain this
compatibility code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:51 -07:00
Brian Behlendorf
e5b65e3179 Remove uintptr_t typedef
The uintptr_t typedef has been available since Linux 2.6.24.
There is no longer a need to maintain this compatibility code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:50 -07:00
Brian Behlendorf
ff0582cb39 Remove atomic64_xchg() wrappers
The atomic64_xchg() and atomic64_cmpxchg() functions have been
available since Linux 2.6.24.  There is no longer a need to
maintain this compatibility code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:50 -07:00
Brian Behlendorf
82f2f1a3af Simplify the time compatibility wrappers
Many of the time functions had grown overly complex in order to
handle kernel compatibility issues.  However, as of Linux 2.6.26
all the required functionality is available.  This allows us to
retire numerous configure checks and greatly simplify the time
compatibility wrappers.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:50 -07:00
Brian Behlendorf
87f8055a91 Map highbit64() to fls64()
The fls64() function has been available since Linux 2.6.16 and
it should be used to implemented highbit64().  This allows us
to provide an optimized implementation and simplify the code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:50 -07:00
Brian Behlendorf
9c91800d19 Remove CTL_UNNUMBERED sysctl interface
Support for the CTL_UNNUMBERED sysctl interface was removed in
Linux 2.6.19.  There is no longer any reason to maintain this
compatibility code.  There also issue any reason to keep around
the CTL_NAME macro and helpers so they have been retired.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:50 -07:00
Brian Behlendorf
b38bf6a4e3 Remove register_sysctl() compatibility code
The register_sysctl() interface has been stable since Linux 2.6.21.
There is no longer a need to maintain compatibility code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:50 -07:00
Brian Behlendorf
bb4dee3df2 Remove utsname() wrapper
There is no longer a need to wrap this because utsname() is provided
by the kernel and can be called directly.  This will require a small
change in the ZFS code because utsname is expected to be a global
structure and not a function.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:11:41 -07:00
Brian Behlendorf
aa363c5c05 Remove sysctl_vfs_cache_pressure assumption
The generic SPL cache shrinkers make the assumption that the
caches only contain VFS cache data and therefore should be scaled
based on vfs_cache_pressure.  This is not strictly true and it
should not be assumed.

Removing this tuning should not have any impact on the stock
behavior because vfs_cache_pressure=100 by default.  This means
that no scaling will take place.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:07:28 -07:00
Brian Behlendorf
a80d69caf0 Remove adaptive mutex implementation
Since the Linux 2.6.29 kernel all mutexes have been adaptive mutexs.
There is no longer any point in keeping this code so it is being
removed to simplify the code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:07:28 -07:00
Brian Behlendorf
56cfabd3e8 Remove patches directory
There is no longer a need to carry these stale patches in the
SPL source tree.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:07:28 -07:00
Brian Behlendorf
3a92530563 Update code to use misc_register()/misc_deregister()
When the SPL was originally written it was designed to use the
device_create() and device_destroy() functions.  Unfortunately,
these functions changed considerably over the years making them
difficult to rely on.

As it turns out a better choice would have been to use the
misc_register()/misc_deregister() functions.  This interface
for registering character devices has remained stable, is simple,
and provides everything we need.

Therefore the code has been reworked to use this interface.  The
higher level ZFS code has always depended on these same interfaces
so this is also as a step towards minimizing our kernel dependencies.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:07:28 -07:00
Brian Behlendorf
0cb3dafccd Update SPLAT to use kmutex_t for portability
For consistency throughout the code update the SPLAT infrastructure
to use the wrapped mutex interfaces.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:07:28 -07:00
Brian Behlendorf
6203295438 Make license compatibility checks consistent
Apply the license specified in the META file to ensure the
compatibility checks are all performed consistently.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-17 15:07:28 -07:00
Darik Horn
d94fd5f0de Let zpool import ignore a missing hostid record.
Change the zpool program to skip its hostid mismatch check in the
same way that libzfs already does.

Invoked imports fail if the ZPOOL_CONFIG_HOSTID nvpair is missing in
the /etc/zfs/zpool.cache file, which can happen as of the /etc/hostid
deprecation in commit zfsonlinux/spl@acf0ade362.

Signed-off-by: Darik Horn <dajhorn@vanadac.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2794
2014-10-17 14:59:05 -07:00
Brian Behlendorf
33074f2254 Handle NULL mirror child vdev
When selecting a mirror child it's possible that map allocated by
vdev_mirror_map_allc() contains a NULL for the child vdev.  In
this case the child should be skipped and the read issues to
another member of the mirror.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes #1744
2014-10-17 14:59:05 -07:00
Brian Behlendorf
f0e324f25d Update utsname support
Modify the code to use the utsname() kernel function rather than
a global variable.  This results is cleaner more portable code
because utsname() is already provided by the kernel and can be
easily emulated in user space via uname(2).  This means that it
will behave consistently in both contexts.

This is also has the benefit that it allows the removal of a few
_KERNEL pre-processor conditions.  And it also is a pre-requisite
for a proper FUSE port because we need to provide a valid utsname.

Finally, it allows us to remove this functionality from the SPL
and all the related compatibility code.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2757
2014-10-17 14:58:57 -07:00
Brian Behlendorf
050d22b068 Remove shrink_dcache_memory() and shrink_icache_memory()
This functionality is optional and until Linux 3.0, which
provided per-filesystem shinkers, they was never a reasonable
interface.  Therefore, this functionality is being dropped
for earlier kernels.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2757
2014-10-17 14:58:50 -07:00
Brian Behlendorf
60bba62814 Update code to use misc_register()/misc_deregister()
When ZPIOS was originally written it was designed to use the
device_create() and device_destroy() functions.  Unfortunately,
these functions changed considerably over the years making them
difficult to rely on.

As it turns out a better choice would have been to use the
misc_register()/misc_deregister() functions.  This interface
for registering character devices has remained stable, is simple,
and provides everything we need.

Therefore the code has been reworked to use this interface.  The
higher level ZFS code has always depended on these same interfaces
so this is also as a step towards minimizing our kernel dependencies.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2757
2014-10-17 14:58:44 -07:00
Brian Behlendorf
e33045ee98 Make license compatibility checks consistent
Apply the license specified in the META file to ensure the
compatibility checks are all performed consistently.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2757
2014-10-17 14:58:38 -07:00
Ned Bass
e82cdc3acc ztest: print backtrace on SIGSEGV and SIGABRT
Add signal handlers to print a backtrace if we crash or assert.

Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2788
2014-10-13 10:39:39 -07:00
Brian Behlendorf
bf2850de82 Fix source_tree variable in dkms build
The source_tree variable in the previous commit had an extra $.
Remove it so that source_tree is expanded properly.  An identical
fix has been applied in the original patch to the stable branch.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2776
2014-10-13 10:38:41 -07:00
Tom Prince
f178adea81 Point dkms build at installed source tree, rather than build directory.
Signed-off-by: Tom Prince <tom.prince@clusterhq.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2776
2014-10-09 12:05:43 -07:00
Tom Prince
fee48fd22c Install header during post-build rather than post-install.
New versions of dkms clean up the build directory after installing.

It appears that this was always intended, but had rm -rf "/path/to/build/*"
(note the quotes), which prevented it from working.

Also, the build step is already installing stuff into the directory where
these files go, so installing our stuff there as part of build rather than
install makes sense.

Signed-off-by: Tom Prince <tom.prince@clusterhq.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2776
2014-10-09 12:03:50 -07:00
Tom Prince
de2a22fcb3 Install header during post-build rather than post-install.
New versions of dkms clean up the build directory after installing.

It appears that this was always intended, but had rm -rf "/path/to/build/*"
(note the quotes), which prevented it from working.

Also, the build step is already installing stuff into the directory where
these files go, so installing our stuff there as part of build rather than
install makes sense.

Signed-off-by: Tom Prince <tom.prince@clusterhq.com>
Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #399
2014-10-09 12:00:25 -07:00
Turbo Fredriksson
971808ec9f Add a stern warning about dedup
Users intending to use dedup should be clearly advised about
its memory requirements and the risks involved.

Thanx to Sachiru for comments and suggestions.

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2754
2014-10-08 17:07:11 -07:00
Brian Behlendorf
e6659763c6 Improve VERIFY() error in dmu_write()
This is a debug patch designed to ensure an error code is logged
to the console when this VERIFY() is hit.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Issue #1440
2014-10-08 09:18:14 -07:00
Brian Behlendorf
8878261fc9 Fix CPU_SEQID use in preemptible context
Commit e022864 introduced a regression for kernels which are built
with CONFIG_DEBUG_PREEMPT.  The use of CPU_SEQID in a preemptible
context causes zio_nowait() to trigger the BUG.  Since CPU_SEQID
is simply being used as a random index the usage here is safe. To
resolve the issue preempt is disable while calling CPU_SEQID.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes #2769
2014-10-07 16:40:29 -07:00
Turbo Fredriksson
a215ee16c0 Add an example for 'zfs bookmark' to the Example section.
Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2762
2014-10-07 11:29:26 -07:00
Matthew Ahrens
e022864d19 Illumos 5176 - lock contention on godfather zio
5176 lock contention on godfather zio
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Alex Reece <alex.reece@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Richard Elling <richard.elling@gmail.com>
Reviewed by: Bayard Bell <Bayard.Bell@nexenta.com>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
  https://www.illumos.org/issues/5176
  https://github.com/illumos/illumos-gate/commit/6f834bc

Porting notes:

Under Linux max_ncpus is defined as num_possible_cpus().  This is
largest number of cpu ids which might be available during the life
time of the system boot.  This value can be larger than the number
of present cpus if CONFIG_HOTPLUG_CPU is defined.

Ported by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2711
2014-10-07 11:24:24 -07:00
Lukas Wunner
07a3312f17 Amend Dracut module to export ZFS root on shutdown
Make use of Dracut's ability to restore the initramfs on shutdown and
pivot to it, allowing for a clean unmount and export of the ZFS root.
No need to force-import on every reboot anymore.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2195
Issue #2476
Issue #2498
Issue #2556
Issue #2563
Issue #2575
Issue #2600
Issue #2755
Issue #2766
2014-10-07 10:20:56 -07:00
Chris Dunlap
8ac9b5e6b5 Cleanup struct zed_conf vars in zed_conf_destroy
Reset struct zed_conf file descriptors to -1 after close(),
and pointers to NULL after free().

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2756
2014-10-06 13:18:11 -07:00
Chris Dunlap
56697c4264 Obtain advisory lock on ZED PID file
ZED uses an advisory lock on its state file to protect against
multiple instances running concurrently.  However, work is planned
to move this state information into the kernel, and ZED will still
need to protect against starting multiple instances.

This commit adds an advisory lock on the PID file to protect against
starting multiple instances.  A lock failure can be overridden with
the "-f" (force) command-line option.  The advisory lock on the state
file is being retained for as long as the state information is stored
in the state file.

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2756
2014-10-06 13:17:40 -07:00
Brian Behlendorf
81857a34d1 Fix bug in SPLAT taskq:front
While running SPLAT on a kernel with CONFIG_DEBUG_ATOMIC_SLEEP
enabled the taskq:front was flagged as a test which might sleep
which in an unsafe context.  Specifically, the splat_vprint()
function which internally takes a mutex was being called under
a spin lock.  Moving the log function outside the spin lock
cleanly solves this issue.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2014-10-03 10:42:20 -07:00
Andriy Gapon
057485504e zfs send -p send properties only for snapshots that are actually sent
... as opposed to sending properties of all snapshots of the relevant
filesystem.  The previous behavior results in properties being set on
all snapshots on the receiving side, which is quite slow.

Behavior of zfs send -R is not changed.

References:
  http://thread.gmane.org/gmane.comp.file-systems.openzfs.devel/346

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2729
Issue #2210
2014-10-02 16:52:02 -07:00
smh
7509a3d299 FreeBSD PR kern/172259: Fixes zfs receive errors
FreeBSD PR kern/172259: Fixes zfs receive errors caused by snapshot
replication being processed in a random order instead of creation
order.

Eliminates needless filesystem renames caused by removed parent
snapshots which subsequently causes many more errors.

PR:		kern/172259
Submitted by:	Steven Hartland
Reviewed by:	pjd (mentor)
Approved by:	pjd (mentor)
MFC after:	2 weeks

References:
  https://github.com/freebsd/freebsd/commit/4995789

Porting notes:

Minor whitespace fixes were made to conform with style requirements:

lib/libzfs/libzfs_sendrecv.c: 2269: indent by spaces instead of tabs
lib/libzfs/libzfs_sendrecv.c: 2270: indent by spaces instead of tabs

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2729
2014-10-02 16:48:19 -07:00
Richard Yao
83e9986f6e Implement -t option to zpool create for temporary pool names
Creating virtual machines that have their rootfs on ZFS on hosts that
have their rootfs on ZFS causes SPA namespace collisions when the
standard name rpool is used. The solution is either to give each guest
pool a name unique to the host, which is not always desireable, or boot
a VM environment containing an ISO image to install it, which is
cumbersome.

26b42f3f9d introduced `zpool import -t
...` to simplify situations where a host must access a guest's pool when
there is a SPA namespace conflict. We build upon that to introduce
`zpool import -t tname ...`. That allows us to create a pool whose
in-core name is tname, but whose on-disk name is the normal name
specified.

This simplifies the creation of machine images that use a rootfs on ZFS.
That benefits not only real world deployments, but also ZFSOnLinux
development by decreasing the time needed to perform rootfs on ZFS
experiments.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2417
2014-09-30 10:46:59 -07:00
Richard Yao
00d2a8c92f zpool import -t should not update cachefile
zpool import's -t parameter is intended for use with -R when operating
on pools that belong to other systems. Like -R, pools imported in this
way should not update the cachefile unless explicitly requested. The
initial implementation allowed the cachefile to be updated when -R was
not used. This went uncaught during testing because -R had implicitly
disabled use of the cachefile.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2417
2014-09-30 10:46:58 -07:00
Richard Yao
2f3ec90061 Add add_prop_list_default helper
Adding to a property list only if there is no existing value is used
twice. Once by zpool create -R and again by zpool import -R. Now that
zpool create -t and zpool import -t also need it, lets refactor it into
a helper function to make the code more readable.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #2417
2014-09-30 10:46:58 -07:00
Brian Behlendorf
aa0ac7caa4 Make user stack limit configurable
To aid in detecting and debugging stack overflow issues make the
user space stack limit configurable via a new ZFS_STACK_SIZE
environment variable.  The value assigned to ZFS_STACK_SIZE will
be used as the default stack size in bytes.

Because this is mainly useful as a debugging aid in conjunction
with ztest the stack limit is disabled by default.  See the ztest(1)
man page for additional details on using the ZFS_STACK_SIZE
environment variable.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ned Bass <bass6@llnl.gov>
Closes #2743
Issue #2293
2014-09-30 10:46:55 -07:00
Tim Chase
cb08f06307 Perform whole-page page truncation for hole-punching under a range lock
As an attempt to perform the page truncation more optimally, the
hole-punching support added in 223df0161f
truncated performed the operation in two steps: first, sub-page "stubs"
were zeroed under the range lock in zfs_free_range() using the new
zfs_zero_partial_page() function and then the whole pages were truncated
within zfs_freesp().  This left a window of opportunity during which
the full pages could be touched.

This patch closes the window by moving the whole-page truncation into
zfs_free_range() under the range lock.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2733
2014-09-29 09:22:03 -07:00
Chris Dunlap
dcca723ace Refer to ZED's scripts as ZEDLETs
The executables invoked by the ZED in response to a given zevent
have been generically referred to as "scripts".  By convention,
these scripts have aimed to be /bin/sh compatible for reasons of
portability and comprehensibility.  However, the ZED only requires
they be executable and (ideally) capable of reading environment
variables.  As such, these scripts are now referred to as ZEDLETs
(ZFS Event Daemon Linkage for Executable Tasks).

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2735
2014-09-25 13:54:17 -07:00
Chris Dunlap
8cb8cf91df Replace zed's use of malloc with calloc
When zed allocates memory via malloc(), it typically follows that
with a memset().  However, calloc() implementations can often perform
optimizations when zeroing memory:

https://stackoverflow.com/questions/2688466/why-mallocmemset-is-slower-than-calloc

This commit replaces zed's use of malloc() with calloc().

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2736
2014-09-25 13:43:57 -07:00
Chris Dunlap
bee6665b88 Fix zed io-spare.sh dash incompatibility
The zed's io-spare.sh script defines a vdev_status() function to query
the 'zpool status' output for obtaining the status of a specified vdev.
This function contains a small awk script that uses a parameter
expansion (${parameter/pattern/string}) supported in bash but not
in dash.  Under dash, this fails with a "Bad substitution" error.

This commit replaces the awk script with a (hopefully more portable)
sed script that has been tested under both bash and dash.

Signed-off-by: Chris Dunlap <cdunlap@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2536
2014-09-23 15:32:30 -07:00
Max Grossman
36283ca233 Illumos 5138 - add tunable for maximum number of blocks freed in one txg
Reviewed by: Adam Leventhal <adam.leventhal@delphix.com>
Reviewed by: Mattew Ahrens <mahrens@delphix.com>
Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Reviewed by: Richard Elling <richard.elling@gmail.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/5138
  https://github.com/illumos/illumos-gate/commit/af3465d

Porting notes:

Because support for exposing a uint64_t parameter wasn't added
until v3.17-rc1 the zfs_free_max_blocks variable has been declared
as a unsigned long.  This is already far larger than required and
it allows us to avoid additional autoconf compatibility code.

The default value has been set to 100,000 on Linux instead of
ULONG_MAX which is used on Illumos.  This was done to limit the
number of outstanding IOs in the system when snapshots are destroyed.
This helps ensure individual TXG sync times are kept reasonable and
memory isn't wasted managing a huge backlog of outstanding IOs.

Ported by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2675
Closes #2581
2014-09-23 14:26:34 -07:00