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Fix deadlock on I/O errors during device removal #17145

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merged 1 commit into from
Mar 19, 2025
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Fix deadlock on I/O errors during device removal #17145

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58 changes: 39 additions & 19 deletions module/zfs/vdev_removal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1620,6 +1620,9 @@ spa_vdev_remove_thread(void *arg)
vca.vca_read_error_bytes = 0;
vca.vca_write_error_bytes = 0;

zfs_range_tree_t *segs = zfs_range_tree_create(NULL, ZFS_RANGE_SEG64,
NULL, 0, 0);

mutex_enter(&svr->svr_lock);

/*
Expand All @@ -1632,7 +1635,9 @@ spa_vdev_remove_thread(void *arg)
metaslab_t *msp = vd->vdev_ms[msi];
ASSERT3U(msi, <=, vd->vdev_ms_count);

again:
ASSERT0(zfs_range_tree_space(svr->svr_allocd_segs));
mutex_exit(&svr->svr_lock);

mutex_enter(&msp->ms_sync_lock);
mutex_enter(&msp->ms_lock);
Expand All @@ -1645,36 +1650,49 @@ spa_vdev_remove_thread(void *arg)
}

/*
* If the metaslab has ever been allocated from (ms_sm!=NULL),
* If the metaslab has ever been synced (ms_sm != NULL),
* read the allocated segments from the space map object
* into svr_allocd_segs. Since we do this while holding
* svr_lock and ms_sync_lock, concurrent frees (which
* ms_lock and ms_sync_lock, concurrent frees (which
* would have modified the space map) will wait for us
* to finish loading the spacemap, and then take the
* appropriate action (see free_from_removing_vdev()).
*/
if (msp->ms_sm != NULL) {
VERIFY0(space_map_load(msp->ms_sm,
svr->svr_allocd_segs, SM_ALLOC));

zfs_range_tree_walk(msp->ms_unflushed_allocs,
zfs_range_tree_add, svr->svr_allocd_segs);
zfs_range_tree_walk(msp->ms_unflushed_frees,
zfs_range_tree_remove, svr->svr_allocd_segs);
zfs_range_tree_walk(msp->ms_freeing,
zfs_range_tree_remove, svr->svr_allocd_segs);
if (msp->ms_sm != NULL)
VERIFY0(space_map_load(msp->ms_sm, segs, SM_ALLOC));

/*
* When we are resuming from a paused removal (i.e.
* when importing a pool with a removal in progress),
* discard any state that we have already processed.
*/
zfs_range_tree_clear(svr->svr_allocd_segs, 0,
start_offset);
/*
* We could not hold svr_lock while loading space map, or we
* could hit deadlock in a ZIO pipeline, having to wait for
* it. But we can not block for it here under metaslab locks,
* or it would be a lock ordering violation.
*/
if (!mutex_tryenter(&svr->svr_lock)) {
mutex_exit(&msp->ms_lock);
mutex_exit(&msp->ms_sync_lock);
zfs_range_tree_vacate(segs, NULL, NULL);
mutex_enter(&svr->svr_lock);
goto again;
}

zfs_range_tree_swap(&segs, &svr->svr_allocd_segs);
zfs_range_tree_walk(msp->ms_unflushed_allocs,
zfs_range_tree_add, svr->svr_allocd_segs);
zfs_range_tree_walk(msp->ms_unflushed_frees,
zfs_range_tree_remove, svr->svr_allocd_segs);
zfs_range_tree_walk(msp->ms_freeing,
zfs_range_tree_remove, svr->svr_allocd_segs);

mutex_exit(&msp->ms_lock);
mutex_exit(&msp->ms_sync_lock);

/*
* When we are resuming from a paused removal (i.e.
* when importing a pool with a removal in progress),
* discard any state that we have already processed.
*/
zfs_range_tree_clear(svr->svr_allocd_segs, 0, start_offset);

vca.vca_msp = msp;
zfs_dbgmsg("copying %llu segments for metaslab %llu",
(u_longlong_t)zfs_btree_numnodes(
Expand Down Expand Up @@ -1750,6 +1768,8 @@ spa_vdev_remove_thread(void *arg)

spa_config_exit(spa, SCL_CONFIG, FTAG);

zfs_range_tree_destroy(segs);

/*
* Wait for all copies to finish before cleaning up the vca.
*/
Expand Down
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