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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 |
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| .. | ||
| README.md | ||
| spl-atomic.c | ||
| spl-condvar.c | ||
| spl-cred.c | ||
| spl-err.c | ||
| spl-generic.c | ||
| spl-kmem-cache.c | ||
| spl-kmem.c | ||
| spl-kstat.c | ||
| spl-proc.c | ||
| spl-procfs-list.c | ||
| spl-shrinker.c | ||
| spl-taskq.c | ||
| spl-thread.c | ||
| spl-trace.c | ||
| spl-tsd.c | ||
| spl-vmem.c | ||
| spl-xdr.c | ||
| spl-zlib.c | ||
| spl-zone.c | ||
| THIRDPARTYLICENSE.gplv2 | ||
| THIRDPARTYLICENSE.gplv2.descrip | ||
The Solaris Porting Layer, SPL, is a Linux kernel module which provides a compatibility layer used by the OpenZFS project.
Installation
The latest version of the SPL is maintained as part of this repository. Only when building ZFS version 0.7.x or earlier must an external SPL release be used. These releases can be found at:
- Version 0.7.x: https://github.com/zfsonlinux/spl/tree/spl-0.7-release
- Version 0.6.5.x: https://github.com/zfsonlinux/spl/tree/spl-0.6.5-release
Release
The SPL is released under a GPLv2 license.
For more details see the NOTICE and THIRDPARTYLICENSE files; UCRL-CODE-235197