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
On FreeBSD errno is defined as (* __error()), which means compiler
can't say whether two consecutive reads will return the same.
And without this knowledge the reported error is formally right.
Caching of the errno in local variable fixes the issue.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <robn@despairlabs.com>
Signed-off-by: Alexander Motin <alexander.motin@TrueNAS.com>
Closes#17975
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
Doing it this way means that callers don't have to call
system_taskq_init() and also get the system and system_delay taskqs that
they possibly don't even want.
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
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
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
Only include the zfs headers where they're currently required to
compile. Unfortunately, including zfs_ioctl.h in user space pulls
in a bunch of internal zfs headers as a side effect. We'll need
to move these structures in to a new shared header to avoid this.
We should not need to add the LIBZPOOL_CPPFLAGS when building the
zed, zinject, zpool, libzfs, ior libzfs_core.
Sponsored-by: https://despairlabs.com/sponsor/
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes#17861
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
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
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
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
