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zio: lock parent zios when updating wait counts on reexecute #17016

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Merged
merged 1 commit into from
Feb 4, 2025
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zio: lock parent zios when updating wait counts on reexecute #17016

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18 changes: 17 additions & 1 deletion module/zfs/zio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@
* Copyright (c) 2011, 2022 by Delphix. All rights reserved.
* Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2017, Intel Corporation.
* Copyright (c) 2019, 2023, 2024, Klara Inc.
* Copyright (c) 2019, 2023, 2024, 2025, Klara, Inc.
* Copyright (c) 2019, Allan Jude
* Copyright (c) 2021, Datto, Inc.
* Copyright (c) 2021, 2024 by George Melikov. All rights reserved.
Expand Down Expand Up @@ -2537,13 +2537,29 @@ zio_reexecute(void *arg)
pio->io_state[ZIO_WAIT_READY] = (pio->io_stage >= ZIO_STAGE_READY) ||
(pio->io_pipeline & ZIO_STAGE_READY) == 0;
pio->io_state[ZIO_WAIT_DONE] = (pio->io_stage >= ZIO_STAGE_DONE);

/*
* It's possible for a failed ZIO to be a descendant of more than one
* ZIO tree. When reexecuting it, we have to be sure to add its wait
* states to all parent wait counts.
*
* Those parents, in turn, may have other children that are currently
* active, usually because they've already been reexecuted after
* resuming. Those children may be executing and may call
* zio_notify_parent() at the same time as we're updating our parent's
* counts. To avoid races while updating the counts, we take
* gio->io_lock before each update.
*/
zio_link_t *zl = NULL;
while ((gio = zio_walk_parents(pio, &zl)) != NULL) {
mutex_enter(&gio->io_lock);
for (int w = 0; w < ZIO_WAIT_TYPES; w++) {
gio->io_children[pio->io_child_type][w] +=
!pio->io_state[w];
}
mutex_exit(&gio->io_lock);
}

for (int c = 0; c < ZIO_CHILD_TYPES; c++)
pio->io_child_error[c] = 0;

Expand Down
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