Commit Graph

220 Commits

Author SHA1 Message Date
Alexander Moch
05e2747bf2
Provide loff_t via <fcntl.h> on musl-based Linux systems
Musl exposes loff_t only as a macro in <fcntl.h> when _GNU_SOURCE is
defined. Including <fcntl.h> ensures the type is available, and a
fallback typedef is provided when no macro is defined. This fixes build
failures on musl systems.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <robn@despairlabs.com>
Signed-off-by: Alexander Moch <mail@alexmoch.com>
Closes #18002
2025-12-02 12:14:09 -08:00
Ameer Hamza
88d012a1d6
Fix snapshot automount expiry cancellation deadlock
A deadlock occurs when snapshot expiry tasks are cancelled while holding
locks. The snapshot expiry task (snapentry_expire) spawns an umount
process and waits for it to complete. Concurrently, ARC memory pressure
triggers arc_prune which calls zfs_exit_fs(), attempting to cancel the
expiry task while holding locks. The umount process spawned by the
expiry task blocks trying to acquire locks held by arc_prune, which is
blocked waiting for the expiry task to complete. This creates a circular
dependency: expiry task waits for umount, umount waits for arc_prune,
arc_prune waits for expiry task.

Fix by adding non-blocking cancellation support to taskq_cancel_id().
The zfs_exit_fs() path calls zfsctl_snapshot_unmount_delay() to
reschedule the unmount, which needs to cancel any existing expiry task.
It now uses non-blocking cancellation to avoid waiting while holding
locks, breaking the deadlock by returning immediately when the task is
already running.

The per-entry se_taskqid_lock has been removed, with all taskqid
operations now protected by the global zfs_snapshot_lock held as
WRITER. Additionally, an se_in_umount flag prevents recursive waits when
zfsctl_destroy() is called during unmount. The taskqid is now only
cleared by the caller on successful cancellation; running tasks clear
their own taskqid upon completion.

Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
Closes #17941
2025-12-01 14:43:42 -08:00
Rob Norris
71609a9264 zfs: replace tpool with taskq
They're basically the same thing; lets just carry one.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17948
2025-11-19 08:16:51 -08:00
Rob Norris
23d17f3587 libspl/random: add switch to force pseudo-random numbers for all calls
ztest wants to force all kernel random calls to use the pseudo-random
generator (/dev/urandom), to avoid depleting the system entropy pool
just for testing.

Up until the previous commit, it did this by switching the path that the
libzpool (now libspl) random API would use to get random data from; that
is, it took advantage of an implementation detail.

Now that that hole is closed to it, we need another method. This commit
introduces that; a simple API call to enable/disable "force pseudo"
mode.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:04:30 -08:00
Rob Norris
4d451bae8a libspl: hide global data objects
Currently libspl is a static archive that is linked into multiple shared
objects, which then re-export its symbols. We intend to fix this soon.

For the moment though, most programs shipped with OpenZFS depend on two
or more of these shared objects, and see the same symbols twice. For
functions this is not a problem, as they do not have any mutable state
and so the linker can simply select the first one and use that for all.

For global data objects however, each shared object will have direct
(non-relocatable) references to its own instance of the symbol, such
that changes on one will not necessarily be seen by the other. While
this shouldn't be a problem in practice as these reexported interfaces
are not supposed to be used, they are technically undefined behaviour in
C (C17 6.9.2) and are reported by ASAN as a violation of C++'s "One
Definition Rule".

To fix this, we hide these globals inside their compilation units, and
add access functions and macros as appropriate to preserve the existing
API (though not ABI).

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:04:22 -08:00
Brian Behlendorf
801d9b4f96 debug: move all of the debug bits out of the spl
Pull all of the internal debug infrastructure up in to the zfs
code to clean up the layering.  Remove all the dodgy usage of
SET_ERROR and DTRACE_PROBE from the spl.  Luckily it was
lightly used in the spl layer so we're not losing much.

Sponsored-by: https://despairlabs.com/sponsor/
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:02:51 -08:00
Rob Norris
eceb5b32e9 libspl: move loff_t declaration from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:02:46 -08:00
Rob Norris
5305d0f8b9 zfs_context: move empty __init/__exit macros to sys/debug.h
These are kind-of compiler attribute placeholders, so go here with the
others for now.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:02:42 -08:00
Rob Norris
292438295d libspl: move compiler attribute macros from zfs_context.h
sys/debug.h is not really the right place for them, but we already have
some there for libspl, so it is at least convenient.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:02:35 -08:00
Rob Norris
b9d2e7782f libspl: common sysmacros.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:02:25 -08:00
Rob Norris
248c7ed0d2 libspl: move DTRACE_PROBE macros from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:02:20 -08:00
Rob Norris
03b2e5c40c libspl: move remaining ddi_* prototypes from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:02:12 -08:00
Rob Norris
b5af61b569 libspl: move zone definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:02:00 -08:00
Rob Norris
faa295b9a6 libspl: move SID definitions from zfs_context.h; remove kernel gate
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:01:48 -08:00
Rob Norris
2b4a0dd6c0 libspl: move callb stubs from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:01:44 -08:00
Rob Norris
1911501c7d libspl: move random definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:01:32 -08:00
Rob Norris
daff6b7e35 libspl: move utsname() etc to sys/misc.h; initialise in libspl_init()
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:01:21 -08:00
Rob Norris
6cf6f091cf libspl: move physmem to sys/systm.h; initialise at libspl_init()
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:01:17 -08:00
Rob Norris
0c6be03fd7 zfs_context: remove duplicated access control stuff; remove kernel gate
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:00:52 -08:00
Rob Norris
bca4ca7949 libspl: add include guards for sys/string.h
The extra inclusion via xvattr.h appears to upset the linter in CI. I'm
not entirely sure what its complaint is, but removing sys/string.h
entirely is not quite possible yet, and include guards are rarely a bad
idea, so this will do.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:00:41 -08:00
Rob Norris
db1c58095e libspl: move vattr and xvattr definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:00:24 -08:00
Rob Norris
8b5d919d4e libspl: move kmem definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:00:17 -08:00
Rob Norris
8700fc669b libspl: move procfs_list definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:00:10 -08:00
Rob Norris
ce7a894af1 libspl: move kstat definitions from zfs_context.h, slim down to basics
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 10:00:03 -08:00
Rob Norris
8c022088a7 libspl: move tsd definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:59:59 -08:00
Rob Norris
52cf8eac42 libspl: move cred definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:59:51 -08:00
Rob Norris
a2e10ebfd3 libspl: move taskq definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:59:43 -08:00
Rob Norris
21ae59a53b libspl: move thread definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:59:14 -08:00
Rob Norris
7234d69748 libspl: move cmn_err definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:59:09 -08:00
Rob Norris
a9f3733376 libspl: move condvar definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:58:59 -08:00
Rob Norris
c7eb0a7633 libspl: move rwlock definitions from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:58:50 -08:00
Rob Norris
cc119fbb48 libspl: move mutex headers from zfs_context.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:58:37 -08:00
Rob Norris
ba2ff4b42c libspl: move time definitions from zfs_context_os.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:58:31 -08:00
Rob Norris
37d5df62e0 libzpool: move ZFS-specific headers from libspl
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:58:27 -08:00
Rob Norris
f49b93e2c7 libzpool: move zfs_context_os.h from libspl
Keeping the spl/zfs module split, libzpool is the zfs module for
userspace. Headers and functions specific to it belong there.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:58:18 -08:00
Rob Norris
5588f189a7 libspl: single zfs_context_os.h
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
2025-11-12 09:53:34 -08:00
Brian Behlendorf
64c4b6d17a libspl: hide zfs_tunable_* symbols
The zfs_tunable_* functions are a public interface which are
part of the internal libspl convenience library.  They should
be hidden to prevent an unnecessary ABI change in installed
libraries which link against libspl (e.g. libzfs_core, libuutil).

We do already leak long standing libspl symbols.  This commit is
solely intended to prevent leaking these new ones until this is
properly sorted out.

Reviewed-by: Rob Norris <robn@despairlabs.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #17911
2025-11-12 09:38:54 -08:00
Shreshth3
ea914e4a43
Add missing include statement
Resolve a build failure for user applications that include <sys/uio.h>.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Shreshth Srivastava <shreshthsrivastava2@gmail.com>
Closes #17781
Closes #17814
2025-10-07 09:21:03 -07:00
Paul Dagnelie
d64711c202 Detect a slow raidz child during reads
A single slow responding disk can affect the overall read
performance of a raidz group.  When a raidz child disk is
determined to be a persistent slow outlier, then have it
sit out during reads for a period of time. The raidz group
can use parity to reconstruct the data that was skipped.

Each time a slow disk is placed into a sit out period, its
`vdev_stat.vs_slow_ios count` is incremented and a zevent
class `ereport.fs.zfs.delay` is posted.

The length of the sit out period can be changed using the
`raid_read_sit_out_secs` module parameter.  Setting it to
zero disables slow outlier detection.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Contributions-by: Don Brady <don.brady@klarasystems.com>
Contributions-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #17227
2025-09-10 15:25:03 -07:00
Joel Low
bb9225ea86 Backport AVX2 AES-GCM implementation from BoringSSL
This uses the AVX2 versions of the AESENC and PCLMULQDQ instructions; on
Zen 3 this provides an up to 80% performance improvement.

Original source:
d5440dd2c2/gen/bcm/aes-gcm-avx2-x86_64-linux.S

See the original BoringSSL commit at
3b6e1be439.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Attila Fülöp <attila@fueloep.org>
Signed-off-by: Joel Low <joel@joelsplace.sg>
Closes #17058
2025-08-13 14:51:20 -07:00
Rob Norris
967b15b888 ZIL: allow zil_commit() to fail with error
This changes zil_commit() to have an int return, and updates all callers
to check it. There are no corresponding internal changes yet; it will
always return 0.

Since zil_commit() is an indication that the caller _really_ wants the
associated data to be durability stored, I've annotated it with the
__warn_unused_result__ compiler attribute (via __must_check), to emit a
warning if it's ever ussd without doing something with the return code.
I hope this will mean we never misuse it in the future.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes #17398
2025-08-08 16:43:09 -07:00
Rob Norris
cb9742e532 libspl: add API for manipulating tunables
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17537
2025-07-15 15:46:58 -07:00
Rob Norris
967ce75669 libspl: implement ZFS_MODULE_PARAM for userspace
For each tunable declaration, we create a zfs_tunable_t with its
details, and then a pointer to it in the 'zfs_tunables' ELF section,
that we can access later with a little support from the linker.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17537
2025-07-15 15:46:51 -07:00
Rob Norris
3a494c6d2a mod.h: make consistent across all three platforms
mod.h only exists to include the platform-specific mod_os.h, so we can
get rid of it and just call the platform header mod.h.

Then, create a libspl mod.h, and move the relevant items to it so we can
start building on it.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17537
2025-07-15 15:46:14 -07:00
Rob Norris
1bd225ed8a
abd_os: move headers from libzpool to libspl
5b9e695 added specific userspace versions of abd_os.h and abd_impl_os.h
for libzpool. However, abd.h and abd_impl.h, which include them, are
packaged with libzfs, so other programs building against libzfs can
fail to build, either because the headers aren't installed, or because
they aren't on any standard include path.

So, move abd_os.h and abd_impl_os.h to libspl, where they we will be
installed alongside abd.h and abd_impl.h in a known path.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@klarasystems.com>
Closes #16940
Closes #17390
Closes #17394
2025-05-30 13:38:20 -07:00
Rob Norris
eb9098ed47 SPDX: license tags: CDDL-1.0
Sponsored-by: https://despairlabs.com/sponsor/
Signed-off-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
2025-03-13 17:56:27 -07:00
Brian Atkinson
c6442bd3b6 Removing old code outside of 4.18 kernsls
There were checks still in place to verify we could completely use
iov_iter's on the Linux side. All interfaces are available as of kernel
4.18, so there is no reason to check whether we should use that
interface at this point. This PR completely removes the UIO_USERSPACE
type. It also removes the check for the direct_IO interface checks.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Closes #16856
2024-12-16 10:23:45 -08:00
Martin Matuška
ab777f436c
Return boolean_t in inline functions of lib/libspl/include/sys/uio.h
The inline functions zfs_dio_offset_aligned(), zfs_dio_size_aligned()
and zfs_dio_aligned() are declared as boolean_t but return the bool
type.

This fixes the build of FreeBSD.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Martin Matuska <mm@FreeBSD.org>
Closes #16613
2024-10-07 10:31:46 -07:00
Rich Ercolani
5d01243964
Add SIMD metadata in /proc on Linux
Too many times, people's performance problems have amounted to
"somehow your SIMD support isn't working", and determining that
at runtime is difficult to describe to people.

This adds a /proc/spl/kstat/zfs/simd node, which exposes
metadata about which instructions ZFS thinks it can use,
on AArch64 and x86_64 Linux, to make investigating things
like this much easier.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #16530
2024-09-20 08:16:44 -07:00
Brian Atkinson
a10e552b99
Adding Direct IO Support
Adding O_DIRECT support to ZFS to bypass the ARC for writes/reads.

O_DIRECT support in ZFS will always ensure there is coherency between
buffered and O_DIRECT IO requests. This ensures that all IO requests,
whether buffered or direct, will see the same file contents at all
times. Just as in other FS's , O_DIRECT does not imply O_SYNC. While
data is written directly to VDEV disks, metadata will not be synced
until the associated  TXG is synced.
For both O_DIRECT read and write request the offset and request sizes,
at a minimum, must be PAGE_SIZE aligned. In the event they are not,
then EINVAL is returned unless the direct property is set to always (see
below).

For O_DIRECT writes:
The request also must be block aligned (recordsize) or the write
request will take the normal (buffered) write path. In the event that
request is block aligned and a cached copy of the buffer in the ARC,
then it will be discarded from the ARC forcing all further reads to
retrieve the data from disk.

For O_DIRECT reads:
The only alignment restrictions are PAGE_SIZE alignment. In the event
that the requested data is in buffered (in the ARC) it will just be
copied from the ARC into the user buffer.

For both O_DIRECT writes and reads the O_DIRECT flag will be ignored in
the event that file contents are mmap'ed. In this case, all requests
that are at least PAGE_SIZE aligned will just fall back to the buffered
paths. If the request however is not PAGE_SIZE aligned, EINVAL will
be returned as always regardless if the file's contents are mmap'ed.

Since O_DIRECT writes go through the normal ZIO pipeline, the
following operations are supported just as with normal buffered writes:
Checksum
Compression
Encryption
Erasure Coding
There is one caveat for the data integrity of O_DIRECT writes that is
distinct for each of the OS's supported by ZFS.
FreeBSD - FreeBSD is able to place user pages under write protection so
          any data in the user buffers and written directly down to the
	  VDEV disks is guaranteed to not change. There is no concern
	  with data integrity and O_DIRECT writes.
Linux - Linux is not able to place anonymous user pages under write
        protection. Because of this, if the user decides to manipulate
	the page contents while the write operation is occurring, data
	integrity can not be guaranteed. However, there is a module
	parameter `zfs_vdev_direct_write_verify` that controls the
	if a O_DIRECT writes that can occur to a top-level VDEV before
	a checksum verify is run before the contents of the I/O buffer
        are committed to disk. In the event of a checksum verification
	failure the write will return EIO. The number of O_DIRECT write
	checksum verification errors can be observed by doing
	`zpool status -d`, which will list all verification errors that
	have occurred on a top-level VDEV. Along with `zpool status`, a
	ZED event will be issues as `dio_verify` when a checksum
	verification error occurs.

ZVOLs and dedup is not currently supported with Direct I/O.

A new dataset property `direct` has been added with the following 3
allowable values:
disabled - Accepts O_DIRECT flag, but silently ignores it and treats
	   the request as a buffered IO request.
standard - Follows the alignment restrictions  outlined above for
	   write/read IO requests when the O_DIRECT flag is used.
always   - Treats every write/read IO request as though it passed
           O_DIRECT and will do O_DIRECT if the alignment restrictions
	   are met otherwise will redirect through the ARC. This
	   property will not allow a request to fail.

There is also a module parameter zfs_dio_enabled that can be used to
force all reads and writes through the ARC. By setting this module
parameter to 0, it mimics as if the  direct dataset property is set to
disabled.

Reviewed-by: Brian Behlendorf <behlendorf@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Co-authored-by: Mark Maybee <mark.maybee@delphix.com>
Co-authored-by: Matt Macy <mmacy@FreeBSD.org>
Co-authored-by: Brian Behlendorf <behlendorf@llnl.gov>
Closes #10018
2024-09-14 13:47:59 -07:00