Re: [PATCH v2 2/3] btrfs: zoned: fix write time activation failure for metadata block group

[Naohiro Aota <Naohiro.Aota@wdc.com>]

On Fri Jul 11, 2025 at 7:52 PM JST, Johannes Thumshirn wrote:
> On 11.07.25 09:24, Naohiro Aota wrote:
>> +	if (block_group->flags & BTRFS_BLOCK_GROUP_DATA) {
>> +		/* The caller should check if the block group is full. */
>> +		if (WARN_ON_ONCE(btrfs_zoned_bg_is_full(block_group))) {
>
> I get that WARN_ON() triggering when running fio benchmarks:
>
>
> [ 2054.634831] RIP: 0010:btrfs_zone_activate+0x1e0/0x220 [btrfs]
> [ 2054.660477] RSP: 0018:ffffd20f0bd039b8 EFLAGS: 00010246
> [ 2054.666069] RAX: 0000000010000000 RBX: ffff8b7d98747c00 RCX: ffff8b7d4729f508
> [ 2054.673576] RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffff8b7d98747c10
> [ 2054.681069] RBP: 0000000000000000 R08: ffff8b7d5c13b000 R09: 0000000000000000
> [ 2054.688563] R10: ffff8b9c88239480 R11: 0000000000000001 R12: ffff8b7d5c13b000
> [ 2054.696050] R13: ffff8b7d5315b000 R14: ffff8b7d47389400 R15: 0000000000001000
> [ 2054.703546] FS:  00007ff45a4b2840(0000) GS:ffff8b9d02a7e000(0000) knlGS:0000000000000000
> [ 2054.711989] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 2054.718090] CR2: 000056051a88df6c CR3: 000000034dbc0000 CR4: 0000000000350ef0
> [ 2054.725581] Call Trace:
> [ 2054.728392]  <TASK>
> [ 2054.730854]  ? srso_return_thunk+0x5/0x5f
> [ 2054.735233]  ? btrfs_zoned_reserve_data_reloc_bg+0x77/0x230 [btrfs]
> [ 2054.741915]  open_ctree+0x7e9/0xb40 [btrfs]
>
> But before that I see write time errors:
>
> [  203.230377] BTRFS info (device sdh): host-managed zoned block device /dev/sdh, 111760 zones of 268435456 bytes
> [  203.240465] BTRFS info (device sdh): zoned mode enabled with zone size 268435456
> [  203.251064] BTRFS info (device sdh): checking UUID tree
> [ 1958.689947] sdh: zone 1324: Aborting plugged BIOs
> [ 1958.694697] BTRFS error (device sdh): bdev /dev/sdh errs: wr 1, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.703428] BTRFS error (device sdh): bdev /dev/sdh errs: wr 2, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.712157] BTRFS error (device sdh): bdev /dev/sdh errs: wr 3, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.720881] BTRFS error (device sdh): bdev /dev/sdh errs: wr 4, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.729614] BTRFS error (device sdh): bdev /dev/sdh errs: wr 5, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.738345] BTRFS error (device sdh): bdev /dev/sdh errs: wr 6, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.747072] BTRFS error (device sdh): bdev /dev/sdh errs: wr 7, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.755798] BTRFS error (device sdh): bdev /dev/sdh errs: wr 8, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.764525] BTRFS error (device sdh): bdev /dev/sdh errs: wr 9, rd 0, flush 0, corrupt 0, gen 0
> [ 1958.773257] BTRFS error (device sdh): bdev /dev/sdh errs: wr 10, rd 0, flush 0, corrupt 0, gen 0
> [ 1959.306908] BTRFS error (device sdh state A): Transaction aborted (error -5)
> [ 1959.314030] BTRFS: error (device sdh state A) in __btrfs_update_delayed_inode:1015: errno=-5 IO failure
> [ 1959.323481] BTRFS info (device sdh state EA): forced readonly
> [ 1959.536934] sdh: zone 1325: Aborting plugged BIOs
>
>
> This is with today's for-next and the two patch sets of you applied. Will dig deeper.

Ah, yes. I know this issue. This happens because
btrfs_zoned_reserve_data_reloc_bg() uses "if (bg->used > 0)" to choose
(skip) a block group to be reserved. If a block group is fully allocated
and get unused, bg->used == 0 && bg->alloc_offset != 0. Since, reserving
this block group itself is an issue. I should have included the fix for
this. I'll update this series to include the fix.