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Recieving a stream with the large microzap feature flag is not properly recorded #18143
Description
System information
| Type | Version/Name |
|---|---|
| Distribution Name | Ubuntu |
| Distribution Version | 25.10 |
| Kernel Version | 6.17.0-8-generic |
| Architecture | x86_64 |
| OpenZFS Version | zfs-2.3.4-1ubuntu2 , zfs-kmod-2.3.4-1ubuntu2 |
Describe the problem you're observing
When receiving a stream with the large microzap feature is enabled, the activation is not properly recorded. There are two distinct issues:
- The in-memory status of the feature is not recorded. This causes sends of the received dataset to not included the large microzap feature flag.
- The feature can attempt to be activated multiple times, causing a panic.
Describe how to reproduce the problem
echo 1048576 >> /sys/module/zfs/parameters/zap_micro_max_size
dd if=/dev/zero of=./test.zfs bs=1M count=128
zpool create test `pwd`/test.zfs
zpool set feature@large_microzap=enabled test
zpool get feature@large_microzap test
zfs create test/src
cd /test/src
seq 1 4096 | xargs touch
zfs snap test/src@snap
zfs send -L test/src@snap | zfs recv test/dest
# The feature is not recorded as active in the test/third's dataset extensions
zfs send -L test/dest@snap | zfs recv test/third
# sync so we can inspect the on disk structures
zpool sync test
zfs snap test/src@second
# The receive panics
zfs send -L -i test/src@snap test/src@second | zfs recv -F test/destI was not sure how to inspect the dataset extensions for test/third using zdb. I instead used my c# program to dump them and verify the large dataset feature was not activated.
Include any warning/errors/backtraces from the system logs
VERIFY0(zap_add(mos, dsobj, spa_feature_table[f].fi_guid, sizeof (zero), 1, &zero, tx)) failed (17)
PANIC at dsl_dataset.c:1139:dsl_dataset_activate_feature()
Showing stack for process 3101
CPU: 24 UID: 0 PID: 3101 Comm: txg_sync Tainted: P OE 6.14.0-37-generic #37~24.04.1-Ubuntu
Tainted: [P]=PROPRIETARY_MODULE, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x76/0xa0
dump_stack+0x10/0x20
spl_dumpstack+0x28/0x40 [spl]
spl_panic+0xfc/0x120 [spl]
? zap_add+0x83/0xc0 [zfs]
dsl_dataset_activate_feature+0x1a9/0x290 [zfs]
dsl_dataset_clone_swap_sync_impl+0x9cd/0xf40 [zfs]
? dmu_buf_rele+0x3a/0x50 [zfs]
? dsl_dir_rele+0x31/0x40 [zfs]
dmu_recv_end_sync+0x274/0x5d0 [zfs]
dsl_sync_task_sync+0xb8/0x110 [zfs]
dsl_pool_sync+0x3ca/0x4e0 [zfs]
spa_sync+0x421/0xda0 [zfs]
? spa_txg_history_set.part.0+0xb1/0x110 [zfs]
? spa_txg_history_init_io+0x120/0x130 [zfs]
txg_sync_thread+0x20a/0x3b0 [zfs]
? __pfx_txg_sync_thread+0x10/0x10 [zfs]
? __pfx_thread_generic_wrapper+0x10/0x10 [spl]
thread_generic_wrapper+0x5e/0x70 [spl]
kthread+0xfe/0x230
? __pfx_kthread+0x10/0x10
ret_from_fork+0x47/0x70
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
Activity
Fix activating large_microzap on receive
Fix activating large_microzap on receive
Fix activating large_microzap on receive
Fix activating large_microzap on receive v2
Fix activating large_microzap on receive