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panic loop when removing slog device

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There is a window in the slog removal code where a panic loop could
ensue if the system crashes during that operation. The original design
of slog removal did not persisted any state because the removal happened
synchronously. This was changed by a later commit which persisted the
vdev_removing flag and exposed this bug. If a slog removal is in
progress and happens to crash after persisting the vdev_removing flag to
the label but before the vdev is removed from the spa config, then the
pool will continue to panic on import. Here's a sample of the panic:

[  134.387411] VERIFY0(0 == dmu_buf_hold_array(os, object, offset, size,
FALSE, FTAG, &numbufs, &dbp)) failed (0 == 22)
[  134.393865] PANIC at dmu.c:1135:dmu_write()
[  134.396035] Kernel panic - not syncing: VERIFY0(0 ==
dmu_buf_hold_array(os, object, offset, size, FALSE, FTAG, &numbufs,
&dbp)) failed (0 == 22)
[  134.397857] CPU: 2 PID: 5914 Comm: txg_sync Kdump: loaded Tainted:
P           OE     5.4.0-1100-dx2023020205-b3751f8c2-azure #106
[  134.407938] Hardware name: Microsoft Corporation Virtual
Machine/Virtual Machine, BIOS 090008  12/07/2018
[  134.407938] Call Trace:
[  134.407938]  dump_stack+0x57/0x6d
[  134.407938]  panic+0xfb/0x2d7
[  134.407938]  spl_panic+0xcf/0x102 [spl]
[  134.407938]  ? traverse_impl+0x1ca/0x420 [zfs]
[  134.407938]  ? dmu_object_alloc_impl+0x3b4/0x3c0 [zfs]
[  134.407938]  ? dnode_hold+0x1b/0x20 [zfs]
[  134.407938]  dmu_write+0xc3/0xd0 [zfs]
[  134.407938]  ? space_map_alloc+0x55/0x80 [zfs]
[  134.407938]  metaslab_sync+0x61a/0x830 [zfs]
[  134.407938]  ? queued_spin_unlock+0x9/0x10 [zfs]
[  134.407938]  vdev_sync+0x72/0x190 [zfs]
[  134.407938]  spa_sync_iterate_to_convergence+0x160/0x250 [zfs]
[  134.407938]  spa_sync+0x2f7/0x670 [zfs]
[  134.407938]  txg_sync_thread+0x22d/0x2d0 [zfs]
[  134.407938]  ? txg_dispatch_callbacks+0xf0/0xf0 [zfs]
[  134.407938]  thread_generic_wrapper+0x83/0xa0 [spl]
[  134.407938]  kthread+0x104/0x140
[  134.407938]  ? kasan_check_write.constprop.0+0x10/0x10 [spl]
[  134.407938]  ? kthread_park+0x90/0x90
[  134.457802]  ret_from_fork+0x1f/0x40

This change no longer persists the vdev_removing flag when removing slog
devices and also cleans up some code that was added which is not used.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Signed-off-by: George Wilson <gwilson@delphix.com>
Closes #14652
This commit is contained in:
George Wilson 2023-03-24 13:27:07 -04:00 committed by GitHub
parent 2bd0490faf
commit 460d887c43
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 14 additions and 23 deletions
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5
include/sys/vdev.h
View File

@ -186,9 +186,8 @@ extern boolean_t vdev_clear_resilver_deferred(vdev_t *vd, dmu_tx_t *tx);
typedef enum vdev_config_flag {
VDEV_CONFIG_SPARE = 1 << 0,
VDEV_CONFIG_L2CACHE = 1 << 1,
VDEV_CONFIG_REMOVING = 1 << 2,
VDEV_CONFIG_MOS = 1 << 3,
VDEV_CONFIG_MISSING = 1 << 4
VDEV_CONFIG_MOS = 1 << 2,
VDEV_CONFIG_MISSING = 1 << 3
} vdev_config_flag_t;
extern void vdev_post_kobj_evt(vdev_t *vd);

30
module/zfs/vdev_label.c
View File

@ -500,7 +500,12 @@ vdev_config_generate(spa_t *spa, vdev_t *vd, boolean_t getstats,
fnvlist_add_uint64(nv, ZPOOL_CONFIG_NONALLOCATING,
vd->vdev_noalloc);
}
if (vd->vdev_removing) {
/*
* Slog devices are removed synchronously so don't
* persist the vdev_removing flag to the label.
*/
if (vd->vdev_removing && !vd->vdev_islog) {
fnvlist_add_uint64(nv, ZPOOL_CONFIG_REMOVING,
vd->vdev_removing);
}
@ -644,35 +649,22 @@ vdev_config_generate(spa_t *spa, vdev_t *vd, boolean_t getstats,
if (!vd->vdev_ops->vdev_op_leaf) {
nvlist_t **child;
int c, idx;
uint64_t c;
ASSERT(!vd->vdev_ishole);
child = kmem_alloc(vd->vdev_children * sizeof (nvlist_t *),
KM_SLEEP);
for (c = 0, idx = 0; c < vd->vdev_children; c++) {
vdev_t *cvd = vd->vdev_child[c];
/*
* If we're generating an nvlist of removing
* vdevs then skip over any device which is
* not being removed.
*/
if ((flags & VDEV_CONFIG_REMOVING) &&
!cvd->vdev_removing)
continue;
child[idx++] = vdev_config_generate(spa, cvd,
for (c = 0; c < vd->vdev_children; c++) {
child[c] = vdev_config_generate(spa, vd->vdev_child[c],
getstats, flags);
}
if (idx) {
fnvlist_add_nvlist_array(nv, ZPOOL_CONFIG_CHILDREN,
(const nvlist_t * const *)child, idx);
}
(const nvlist_t * const *)child, vd->vdev_children);
for (c = 0; c < idx; c++)
for (c = 0; c < vd->vdev_children; c++)
nvlist_free(child[c]);
kmem_free(child, vd->vdev_children * sizeof (nvlist_t *));