Andriy Tkachuk f8457fbdc4 Fix deadlock on dmu_tx_assign() from vdev_rebuild()
vdev_rebuild() is always called with spa_config_lock held in
RW_WRITER mode. However, when it tries to call dmu_tx_assign()
the latter may hang on dmu_tx_wait() waiting for available txg.
But that available txg may not happen because txg_sync takes
spa_config_lock in order to process the current txg. So we have
a deadlock case here:

 - dmu_tx_assign() waits for txg holding spa_config_lock;
 - txg_sync waits for spa_config_lock not progressing with txg.

Here are the stacks:

    __schedule+0x24e/0x590
    schedule+0x69/0x110
    cv_wait_common+0xf8/0x130 [spl]
    __cv_wait+0x15/0x20 [spl]
    dmu_tx_wait+0x8e/0x1e0 [zfs]
    dmu_tx_assign+0x49/0x80 [zfs]
    vdev_rebuild_initiate+0x39/0xc0 [zfs]
    vdev_rebuild+0x84/0x90 [zfs]
    spa_vdev_attach+0x305/0x680 [zfs]
    zfs_ioc_vdev_attach+0xc7/0xe0 [zfs]

    cv_wait_common+0xf8/0x130 [spl]
    __cv_wait+0x15/0x20 [spl]
    spa_config_enter+0xf9/0x120 [zfs]
    spa_sync+0x6d/0x5b0 [zfs]
    txg_sync_thread+0x266/0x2f0 [zfs]

The solution is to pass txg returned by spa_vdev_enter(spa)
at the top of spa_vdev_attach() to vdev_rebuild() and call
dmu_tx_create_assigned(txg) which doesn't wait for txg.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Akash B <akash-b@hpe.com>
Reviewed-by: Alek Pinchuk <apinchuk@axcient.com>
Signed-off-by: Andriy Tkachuk <andriy.tkachuk@seagate.com>
Closes #18210
Closes #18258
2026-02-26 11:18:02 -08:00
2026-02-25 11:20:23 -08:00
2022-12-22 11:34:28 -08:00
2020-06-09 21:24:09 -07:00
2018-05-29 16:00:33 -07:00
2026-02-11 09:37:02 -08:00
2020-08-26 21:44:41 -07:00
2018-05-29 16:00:33 -07:00
2025-11-03 16:37:58 -08:00
2020-03-16 10:46:03 -07:00

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OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.

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Official Resources

Installation

Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.

Contribute & Develop

We have a separate document with contribution guidelines.

We have a Code of Conduct.

Release

OpenZFS is released under a CDDL license. For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197

Supported Kernels

  • The META file contains the officially recognized supported Linux kernel versions.
  • Supported FreeBSD versions are any supported branches and releases starting from 13.0-RELEASE.
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