On 1.03.21 г. 18:15 ч., David Sterba wrote:
> On Mon, Feb 22, 2021 at 06:40:47PM +0200, Nikolay Borisov wrote:
>> btrfs_block_rsv_add can return only ENOSPC since it's called with
>> NO_FLUSH modifier. This so simplify the logic in
>> btrfs_delayed_inode_reserve_metadata to exploit this invariant.
>
> This seems quite fragile, it's not straightforward to see from the
> context that the NO_FLUSH code will always return ENOSPC. I followed a
> few calls down from btrfs_block_rsv_add and it's well hidden inside
> __reserve_bytes. So in case it's an invariant I'd rather add an
> assertion, ie. ASSERT(ret == 0 || ret == -ENOSPC) so at least we know
> when this gets broken. Otherwise looks ok.
>
Fair enough, I'm fine with it. In any case we no longer return eagain
when reserving. either we succeed or we return ENOSPC - either because
we don't have space and we can't flush or because even after the
flushing machinery did its work a ticket still couldn't be satisfied, in
which case we failed it hence ENOSPC got returned.
