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SubjectRe: [PATCH 07/19] btrfs: do sequential extent allocation in HMZONED mode
On Tue, Jun 18, 2019 at 08:28:07AM +0000, Naohiro Aota wrote:
> On 2019/06/13 23:07, Josef Bacik wrote:
> > On Fri, Jun 07, 2019 at 10:10:13PM +0900, Naohiro Aota wrote:
> >> @@ -9616,7 +9701,8 @@ static int inc_block_group_ro(struct btrfs_block_group_cache *cache, int force)
> >> }
> >>
> >> num_bytes = cache->key.offset - cache->reserved - cache->pinned -
> >> - cache->bytes_super - btrfs_block_group_used(&cache->item);
> >> + cache->bytes_super - cache->unusable -
> >> + btrfs_block_group_used(&cache->item);
> >> sinfo_used = btrfs_space_info_used(sinfo, true);
> >>
> >> if (sinfo_used + num_bytes + min_allocable_bytes <=
> >> @@ -9766,6 +9852,7 @@ void btrfs_dec_block_group_ro(struct btrfs_block_group_cache *cache)
> >> if (!--cache->ro) {
> >> num_bytes = cache->key.offset - cache->reserved -
> >> cache->pinned - cache->bytes_super -
> >> + cache->unusable -
> >> btrfs_block_group_used(&cache->item);
> >
> > You've done this in a few places, but not all the places, most notably
> > btrfs_space_info_used() which is used in the space reservation code a lot.
>
> I added "unsable" to struct btrfs_block_group_cache, but added
> nothing to struct btrfs_space_info. Once extent is allocated and
> freed in an ALLOC_SEQ Block Group, such extent is never resued
> until we remove the BG. I'm accounting the size of such region
> in "cache->unusable" and in "space_info->bytes_readonly". So,
> btrfs_space_info_used() does not need the modify.
>
> I admit it's confusing here. I can add "bytes_zone_unusable" to
> struct btrfs_space_info, if it's better.
>

Ah you're right, sorry I just read it as space_info. Yes please add
bytes_zone_unusable, I'd like to be as verbose as possible about where our space
actually is. I know if I go to debug something and see a huge amount in
read_only I'll be confused. Thanks,

Josef

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