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Fix deadlock on dmu_tx_assign() from vdev_rebuild()

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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
This commit is contained in:
Andriy Tkachuk 2026-02-26 19:18:02 +00:00 committed by GitHub
parent f3d4c79496
commit f8457fbdc4
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
3 changed files with 6 additions and 7 deletions
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2
include/sys/vdev_rebuild.h
View File

@ -90,7 +90,7 @@ typedef struct vdev_rebuild {
boolean_t vdev_rebuild_active(vdev_t *);
int vdev_rebuild_load(vdev_t *);
void vdev_rebuild(vdev_t *);
void vdev_rebuild(vdev_t *, uint64_t);
void vdev_rebuild_stop_wait(vdev_t *);
void vdev_rebuild_stop_all(spa_t *);
void vdev_rebuild_restart(spa_t *);

2
module/zfs/spa.c
View File

@ -8484,7 +8484,7 @@ spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot, int replacing,
if (rebuild) {
newvd->vdev_rebuild_txg = txg;
vdev_rebuild(tvd);
vdev_rebuild(tvd, txg);
} else {
newvd->vdev_resilver_txg = txg;

9
module/zfs/vdev_rebuild.c
View File

@ -278,7 +278,7 @@ vdev_rebuild_log_notify(spa_t *spa, vdev_t *vd, const char *name)
* active for the duration of the rebuild, then revert to the enabled state.
*/
static void
vdev_rebuild_initiate(vdev_t *vd)
vdev_rebuild_initiate(vdev_t *vd, uint64_t txg)
{
spa_t *spa = vd->vdev_spa;
@ -286,8 +286,7 @@ vdev_rebuild_initiate(vdev_t *vd)
ASSERT(MUTEX_HELD(&vd->vdev_rebuild_lock));
ASSERT(!vd->vdev_rebuilding);
dmu_tx_t *tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir);
VERIFY0(dmu_tx_assign(tx, DMU_TX_WAIT | DMU_TX_SUSPEND));
dmu_tx_t *tx = dmu_tx_create_assigned(spa_get_dsl(spa), txg);
vd->vdev_rebuilding = B_TRUE;
@ -1015,7 +1014,7 @@ vdev_rebuild_active(vdev_t *vd)
* top-level vdev is currently actively rebuilding.
*/
void
vdev_rebuild(vdev_t *vd)
vdev_rebuild(vdev_t *vd, uint64_t txg)
{
vdev_rebuild_t *vr = &vd->vdev_rebuild_config;
vdev_rebuild_phys_t *vrp __maybe_unused = &vr->vr_rebuild_phys;
@ -1039,7 +1038,7 @@ vdev_rebuild(vdev_t *vd)
if (!vd->vdev_rebuild_reset_wanted)
vd->vdev_rebuild_reset_wanted = B_TRUE;
} else {
vdev_rebuild_initiate(vd);
vdev_rebuild_initiate(vd, txg);
}
mutex_exit(&vd->vdev_rebuild_lock);
}