Re: [PATCH v4] btrfs: zoned: don't force read-only on transient -EAGAIN from reloc merge

On 6/22/26 1:29 PM, Filipe Manana wrote:
> On Mon, Jun 22, 2026 at 9:27 AM Johannes Thumshirn
> <[email protected]> wrote:
>> On a zoned FS, btrfs_delayed_refs_rsv_refill() returns -EAGAIN whenever
>> the over-committed metadata plus the zone_unusable bytes exceeds the
>> usable size in a metadata block-group to avoid heavy over-commit of
>> metadata and early ENOSPC in one transaction.
>>
>> If this happens while doing reclaim, the transaction is getting
>> aborted.
>>
>> Treat -EAGAIN as a soft, retryable condition in case of block-group
>> reclaim.
>>
>> Reported-by: Damien Le Moal <[email protected]>
>> Fixes: 7bcb04de982f ("btrfs: zoned: cap delayed refs metadata reservation to avoid overcommit")
>> Signed-off-by: Johannes Thumshirn <[email protected]>
>> ---
>> Changes to v3:
>> - Don't ASSERT() for zoned in case of EAGAIN in
>>    btrfs_reclaim_block_group but check for zoned
>>
>>   fs/btrfs/block-group.c | 10 +++++++-
>>   fs/btrfs/relocation.c  | 52 ++++++++++++++++++++++++++++++++++++++----
>>   2 files changed, 57 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
>> index ab76a5173272..1327fd526b06 100644
>> --- a/fs/btrfs/block-group.c
>> +++ b/fs/btrfs/block-group.c
>> @@ -2047,6 +2047,12 @@ static int btrfs_reclaim_block_group(struct btrfs_block_group *bg, int *reclaime
>>
>>          trace_btrfs_reclaim_block_group(bg);
>>          ret = btrfs_relocate_chunk(fs_info, bg->start, false);
>> +       if (btrfs_is_zoned(fs_info) && ret == -EAGAIN) {
>> +               btrfs_dec_block_group_ro(bg);
>> +               btrfs_debug(fs_info, "deferring reclaim of chunk %llu",
>> +                           bg->start);
>> +               return ret;
>> +       }
>>          if (ret) {
>>                  btrfs_dec_block_group_ro(bg);
>>                  btrfs_err(fs_info, "error relocating chunk %llu",
>> @@ -2113,7 +2119,9 @@ void btrfs_reclaim_block_groups(struct btrfs_fs_info *fs_info, unsigned int limi
>>                  spin_unlock(&fs_info->unused_bgs_lock);
>>                  ret = btrfs_reclaim_block_group(bg, &reclaimed);
>>
>> -               if (ret && !READ_ONCE(space_info->periodic_reclaim))
>> +               if (ret == -EAGAIN)
>> +                       btrfs_link_bg_list(bg, &retry_list);
>> +               else if (ret && !READ_ONCE(space_info->periodic_reclaim))
>>                          btrfs_link_bg_list(bg, &retry_list);
>>                  btrfs_put_block_group(bg);
>>
>> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
>> index 1819d49d19c3..73d9948b5382 100644
>> --- a/fs/btrfs/relocation.c
>> +++ b/fs/btrfs/relocation.c
>> @@ -1530,6 +1530,36 @@ static void clear_reloc_root(struct btrfs_root *root)
>>          clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
>>   }
>>
>> +/* Drop the reloc trees of a relocation that is being deferred and retried */
> Same comment as in v3: always add punctuation to sentences, this is
> our preferred style.
Yes I apparently sent out the wrong version, also for the if above.