Linux 5.16 moved XSTATE_XSAVE and XSTATE_XRESTORE out of our reach,
so add our own XSAVE{,OPT,S} code and use it for Linux 5.16.
Please note that this differs from previous behavior in that it
won't handle exceptions created by XSAVE an XRSTOR. This is sensible
for three reasons.
- Exceptions during XSAVE and XRSTOR can only occur if the feature
is not supported or enabled or the memory operand isn't aligned
on a 64 byte boundary. If this happens something else went
terribly wrong, and it may be better to stop execution.
- Previously we just printed a warning and didn't handle the fault,
this is arguable for the above reason.
- All other *SAVE instruction also don't handle exceptions, so this
at least aligns behavior.
Finally add a test to catch such a regression in the future.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes#13042Closes#13059
The following commit moved the users of `deferred` into function
dsl_pool_unreserved_space:
commit d2734cce68
Author: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Date: Fri Dec 16 14:11:29 2016 -0800
OpenZFS 9166 - zfs storage pool checkpoint
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <freqlabs@FreeBSD.org>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Christian Schwarz <christian.schwarz@nutanix.com>
Closes#13056
POSIX requires that set-uid and set-gid bits to be removed when an
unprivileged user writes to a file and ZFS does that during normal
operation.
The problem arrises when the write is stored in the ZIL and replayed.
During replay we have no access to original credentials of the process
doing the write, so zfs_write() will be performed with the root
credentials. When root is doing the write set-uid and set-gid bits
are not removed from the file.
To correct that, log a separate TX_SETATTR entry that removed those bits
on first write to such file.
Idea from: Christian Schwarz
Add test for ZIL replay of setuid/setgid clearing.
Improve various edge cases when clearing setid bits:
- The setid bits can be readded during a single write, so make sure to check
for them on every chunk write.
- Log TX_SETATTR record at most once per transaction group (if the setid bits
are keep coming back).
- Move zfs_log_setattr() outside of zp->z_acl_lock.
Reviewed-by: Dan McDonald <danmcd@joyent.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Co-authored-by: Christian Schwarz <me@cschwarz.com>
Signed-off-by: Pawel Jakub Dawidek <pawel@dawidek.net>
Closes#13027
In files created/modified before 4254acb there may be a corruption of
xattrs which is not reported during scrub and normal send/receive. It
manifests only as an error when raw sending/receiving. This happens
because currently only the raw receive path checks for discrepancies
between the dnode bonus length and the spill pointer flag.
In case we encounter a dnode whose bonus length is greater than the
predicted one, we should report an error. Modify in this regard
dnode_sync() with an assertion at the end, dump_dnode() to error out,
dsl_scan_recurse() to report errors during a scrub, and zstream to
report a warning when dumping. Also added a test to verify spill blocks
are sent correctly in a raw send.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes#12720Closes#13014
Add support for http and https to the keylocation properly to
allow encryption keys to be fetched from the specified URL.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Issue #9543Closes#9947Closes#11956
Debian ships fake System.map files by default, leading to the
invocation of depmod with them to flood you with errors about
missing symbols.
Let's notice and not do that.
Reviewed-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes#12862
For kernel to send snapshot mount/unmount events to zed.
For kernel to send symlink creates/removes on zvol plumbing.
(/dev/run/dsk/zvol/$pool/$zvol -> /dev/diskX)
If zed misses the ENODEV, all errors after are EINVAL. Treat any error
as kernel module failure.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Jorgen Lundman <lundman@lundman.net>
Closes#12416
Raw receiving a snapshot back to the originating dataset is currently
impossible because of user accounting being present in the originating
dataset.
One solution would be resetting user accounting when raw receiving on
the receiving dataset. However, to recalculate it we would have to dirty
all dnodes, which may not be preferable on big datasets.
Instead, we rely on the os_phys flag
OBJSET_FLAG_USERACCOUNTING_COMPLETE to indicate that user accounting is
incomplete when raw receiving. Thus, on the next mount of the receiving
dataset the local mac protecting user accounting is zeroed out.
The flag is then cleared when user accounting of the raw received
snapshot is calculated.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes#12981Closes#10523Closes#11221Closes#11294Closes#12594
Issue #11300
When using the two argument version of submit_bio() in kernel's prior
to 4.8 the first argument should be specified. It's used by block
dump to report the bio direction.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Finix Yan <yancw@info2soft.com>
Closes#13006
Linux 5.17 sees a rename from complete_and_exit()
to kthread complete_and_exit()
Upstream commit cead18552660702a4a46f58e65188fe5f36e9dfe
("exit: Rename complete_and_exit to kthread_complete_and_exit")
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes#12989
For us, I think it's always just FALLOC_FL_PUNCH_HOLE with a fake
mustache on.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Coleman Kane <ckane@colemankane.org>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes#12975
add_disk went from void to must-check int return.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Coleman Kane <ckane@colemankane.org>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes#12975
FreeBSD's implementation of zfs_uio_fault_move() returns EFAULT when a
page fault occurs while copying data in or out of user buffers. The VFS
treats such errors specially and will retry the I/O operation (which may
have made some partial progress).
When the FreeBSD and Linux implementations of zfs_write() were merged,
the handling of errors from dmu_write_uio_dbuf() changed such that
EFAULT is not handled as a partial write. For example, when appending
to a file, the z_size field of the znode is not updated after a partial
write resulting in EFAULT.
Restore the old handling of errors from dmu_write_uio_dbuf() to fix
this. This should have no impact on Linux, which has special handling
for EFAULT already.
Reviewed-by: Andriy Gapon <avg@FreeBSD.org>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Closes#12964
When the eviction thread goes to shrink an ARC state, it allocates a set
of marker buffers used to hold its place in the state's sublists.
This can be problematic in low memory conditions, since
1) the allocation can be substantial, as we allocate NCPU markers;
2) on at least FreeBSD, page reclamation can block in
arc_wait_for_eviction()
In particular, in stress tests it's possible to hit a deadlock on
FreeBSD when the number of free pages is very low, wherein the system is
waiting for the page daemon to reclaim memory, the page daemon is
waiting for the ARC eviction thread to finish, and the ARC eviction
thread is blocked waiting for more memory.
Try to reduce the likelihood of such deadlocks by pre-allocating markers
for the eviction thread at ARC initialization time. When evicting
buffers from an ARC state, check to see if the current thread is the ARC
eviction thread, and use the pre-allocated markers for that purpose
rather than dynamically allocating them.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: George Amanakis <gamanakis@gmail.com>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Closes#12985
First open locking changes were correctly applied to zvol_geom_open but
incorrectly applied to zvol_cdev_open, causing spa_namespace_lock to be
held indefinitely.
Make the first open locking in zvol_cdev_open match zvol_geom_open.
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes#13016
These are the changes for FreeBSD corresponding to the changes made for
Linux in #12863, see that PR for details.
Changes from #12863 are applied for zvol_geom_open and zvol_cdev_open
on FreeBSD. This also adds a check for the zvol dying which we had
in zvol_geom_open but was missing in zvol_cdev_open. The check causes
the open to fail early with ENXIO when we are in the middle of changing
volmode.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes#12934
Fix from https://github.com/openzfs/zfs/pull/12844#discussion_r774179413
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes#12905
sc.nr_to_scan is an input to super_cache_clean (via
shrinker->scan_objects), used to set the number of objects to scan
in the various caches. However super_cache_scan also modifies
sc.nr_to_scan, so when used in a loop we need to reset
sc.nr_to_scan back to our desired nr_to_scan for the next
iteration.
Issue discovered and solution suggested by
Tenzin Lhakhang @tlhakhan.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chris Dunlop <chris@onthe.net.au>
Issue #12433Closes#12908
Verify that all empty sectors are zero filled before using them to
calculate parity. Failure to do so can result in incorrect parity
columns being generated and written to disk if the contents of an
empty sector are non-zero. This was possible because the checksum
only protects the data portions of the buffer, not the empty sector
padding.
This issue has been addressed by updating raidz_parity_verify() to
check that all dRAID empty sectors are zero filled. Any sectors
which are non-zero will be fixed, repair IO issued, and a checksum
error logged. They can then be safely used to verify the parity.
This specific type of damage is unlikely to occur since it requires
a disk to have silently returned bad data, for an empty sector, while
performing a scrub. However, if a pool were to have been damaged
in this way, scrubbing the pool with this change applied will repair
both the empty sector and parity columns as long as the data checksum
is valid. Checksum errors will be reported in the `zpool status`
output for any repairs which are made.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#12857
When performing I/O on FreeBSD using a file based vdev ensure all
errors encountered when reading/writing are propagated through the
zio pipeline.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes#12904
When restructuring the zvol_open() logic for the Linux 5.13 kernel
a lock inversion was accidentally introduced. In the updated code
the spa_namespace_lock is now taken before the zv_suspend_lock
allowing the following scenario to occur:
down_read <=== waiting for zv_suspend_lock
zvol_open <=== holds spa_namespace_lock
__blkdev_get
blkdev_get_by_dev
blkdev_open
...
mutex_lock <== waiting for spa_namespace_lock
spa_open_common
spa_open
dsl_pool_hold
dmu_objset_hold_flags
dmu_objset_hold
dsl_prop_get
dsl_prop_get_integer
zvol_create_minor
dmu_recv_end
zfs_ioc_recv_impl <=== holds zv_suspend_lock via zvol_suspend()
zfs_ioc_recv
...
This commit resolves the issue by moving the acquisition of the
spa_namespace_lock back to after the zv_suspend_lock which restores
the original ordering.
Additionally, as part of this change the error exit paths were
simplified where possible.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#12863
A recent commit to FreeBSD changed the type of
vop_readdir_args.a_cookies to a uint64_t**. There is no functional
impact to ZFS because ZFS only uses 32-bit cookies, which will be
zero-extended to 64-bits by the existing code.
b214fcceac
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Alan Somers <asomers@gmail.com>
Closes#12874
On FreeBSD vnode reclamation is single-threaded, protected by single
global lock. Linux seems to be able to use a thread per mount point,
but at this time it creates more harm than good.
Reduce number of threads to 1, adding tunable in case somebody wants
to try more.
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Chris Dunlop <chris@onthe.net.au>
Reviewed-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Closes#12896
Issue #9966
va_seq was actually a thin veil over va_gen, so z_gen is a more
appropriate value than z_seq to populate the field with.
Drop the unnecessary compat obfuscation and provide the correct
file generation number.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Ryan Moeller <freqlabs@freebsd.org>
Closes#12851
- To avoid a use-after-free, zfsvfs->z_log needs to be loaded after the
teardown lock is acquired with ZFS_ENTER().
- Avoid leaking vnode locks in zfs_rename_relock() and zfs_rename_()
when the ZFS_ENTER() macros forces an early return.
Refactor the rename implementation so that ZFS_ENTER() can be used
safely. As a bonus, this lets us use the ZFS_VERIFY_ZP() macro instead
of open-coding its implementation.
Reported-by: Peter Holm <pho@FreeBSD.org>
Tested-by: Peter Holm <pho@FreeBSD.org>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Sponsored-by: The FreeBSD Foundation
Closes#12717
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Pawel Jakub Dawidek <pawel@dawidek.net>
Closes#12748
We have to hold the teardown lock while dereferencing zfsvfs->z_os and,
I believe, when committing to the ZIL.
Note that jumping to the "out" label, "error" is always non-zero.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Closes#12704
The objset object is reallocated during certain dataset operations, such
as rollbacks, so the objset pointer must be loaded after acquiring the
teardown lock.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Closes#12704
Improve the ability of zfs send to determine if a block is compressed
or not by using information contained in the blkptr.
Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Reviewed-by: Matthew Ahrens <matthew.ahrens@delphix.com>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes#12770
Newer zstd code introduced in the main kernel tree now creates a symbol
collision with ZSTD_isError in our ZSTD code. This change relabels our
implementation with a ZFS-specific symbol name, and undoes some
macro-based micro-optimizations that conflict with the attempt to rename
our internal-use version.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes#12819
The definition of struct blkcg_gq was moved into blk-cgroup.h, which is
a header that's been in Linux since 2015. This is used by
vdev_blkg_tryget() in module/os/linux/zfs/vdev_disk.c. Since the kernel
for CentOS 7 and similar-generation releases doesn't have this header,
its inclusion is guarded by a configure test.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes#12819
This change adds a confiugre check to determine if bio_set_dev is a
helper macro or not. If not, then the attempt to override its internal
call to bio_associate_blkg(), with a macro definition to our own
version, is no longer possible, as the compiler won't use it when
compiling the new inline function replacement implemented in the header.
This change also creates a new vdev_bio_set_dev() function that performs
the same work, and also performs the work implemented in
vdev_bio_associate_blkg(), as it is the only thing calling that function
in our code. Our custom vdev_bio_associate_blkg() is now only compiled
if the bio_set_dev() is a macro in the Linux headers.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes#12819
The iov_iter->type member was renamed iov_iter->iter_type. However,
while looking into this, realized that in 2018 a iov_iter_type(*iov)
accessor function was introduced. So if that is present, use it,
otherwise fall back to trying the existing behavior of directly
accessing type from iov_iter.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes#12819
The return type for the submit_bio member of struct
block_device_operations was changed to no longer return a value.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes#12819
Due to a possible lock inversion the zvol open call path on Linux
needs to be able to retry in the case where the spa_namespace_lock
cannot be acquired.
For Linux 5.12 an older kernel this was accomplished by returning
-ERESTARTSYS from zvol_open() to request that blkdev_get() drop
the bdev->bd_mutex lock, reaquire it, then call the open callback
again. However, as of the 5.13 kernel this behavior was removed.
Therefore, for 5.12 and older kernels we preserved the existing
retry logic, but for 5.13 and newer kernels we retry internally in
zvol_open(). This should always succeed except in the case where
a pool's vdev are layed on zvols, in which case it may fail. To
handle this case vdev_disk_open() has been updated to retry when
opening a device when -ERESTARTSYS is returned.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #12301Closes#12759
Instead, linux/pagemap.h offers a number of folio-specific functions to
be called instead. In this case, module/os/linux/zfs/zfs_vnops_os.c
wants to call wait_on_page_bit(pp, PG_writeback). This gets replaced
with folio_wait_bit(folio_page(pp), PG_writeback). This change modifies
the code to conditionally compile that if configure identifies th
presence of the folio_wait_bit() function.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Coleman Kane <ckane@colemankane.org>
Closes#12800
Userland figures out which encryption-root keys are required to load,
and issues ZFS_IOC_LOAD_KEY.
The tail section of spa_keystore_load_wkey() will call
zvol_create_minors() on the encryption-root object.
Any clones of the encrypted zvol will not be plumbed. This commits
adds additional logic to detect if zvol has clones, and is encrypted,
then adds these to the list of zvols to call zvol_create_minors() on.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Jorgen Lundman <lundman@lundman.net>
Closes#12471
In addition to flushing memory mapped regions when checking holes,
commit de198f2d95 modified the dirty dnode detection logic to check
the dn->dn_dirty_records instead of the dn->dn_dirty_link. Relying
on the dirty record has not be reliable, switch back to the previous
method.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #11900Closes#12745
When using lseek(2) to report data/holes memory mapped regions of
the file were ignored. This could result in incorrect results.
To handle this zfs_holey_common() was updated to asynchronously
writeback any dirty mmap(2) regions prior to reporting holes.
Additionally, while not strictly required, the dn_struct_rwlock is
now held over the dirty check to prevent the dnode structure from
changing. This ensures that a clean dnode can't be dirtied before
the data/hole is located. The range lock is now also taken to
ensure the call cannot race with zfs_write().
Furthermore, the code was refactored to provide a dnode_is_dirty()
helper function which checks the dnode for any dirty records to
determine its dirtiness.
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #11900Closes#12724
The submit_bio() prototype has changed again. The version is 5.16
still only expects a single argument but the return type has changed
to void. Since we never used the returned value before update the
configure check to detect both single arg versions.
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#12725
When you create a pool, zfs writes vd->vdev_enc_sysfs_path with the
enclosure sysfs path to the fault LEDs, like:
vdev_enc_sysfs_path = /sys/class/enclosure/0:0:1:0/SLOT8
However, this enclosure path doesn't get updated on successive imports
even if enclosure path to the disk changes. This patch fixes the issue.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes#11950Closes#12095
As of the Linux 5.9 kernel a fallthrough macro has been added which
should be used to anotate all intentional fallthrough paths. Once
all of the kernel code paths have been updated to use fallthrough
the -Wimplicit-fallthrough option will because the default. To
avoid warnings in the OpenZFS code base when this happens apply
the fallthrough macro.
Additional reading: https://lwn.net/Articles/794944/
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#12441