Re: [PATCH 15/23] btrfs: use ticketing for data space reservations

Josef Bacik
2020-07-07T14:56:04Z

On 7/7/20 10:46 AM, Nikolay Borisov wrote:
>
>
> On 30.06.20 г. 16:59 ч., Josef Bacik wrote:
>> Now that we have all the infrastructure in place, use the ticketing
>> infrastructure to make data allocations. This still maintains the exact
>> same flushing behavior, but now we're using tickets to get our
>> reservations satisfied.
>>
>> Reviewed-by: Nikolay Borisov <nborisov@suse.com>
>> Tested-by: Nikolay Borisov <nborisov@suse.com>
>> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
>> ---
>> fs/btrfs/space-info.c | 125 ++++++++++++++++++++++--------------------
>> 1 file changed, 67 insertions(+), 58 deletions(-)
>>
>> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
>> index 799ee6090693..ee4747917b81 100644
>> --- a/fs/btrfs/space-info.c
>> +++ b/fs/btrfs/space-info.c
>> @@ -1068,6 +1068,54 @@ static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
>> } while (flush_state < states_nr);
>> }
>>
>> +static void priority_reclaim_data_space(struct btrfs_fs_info *fs_info,
>> + struct btrfs_space_info *space_info,
>> + struct reserve_ticket *ticket,
>> + const enum btrfs_flush_state *states,
>> + int states_nr)
>> +{
>> + int flush_state = 0;
>> + int commit_cycles = 2;
>> +
>> + while (!space_info->full) {
>> + flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE);
>> + spin_lock(&space_info->lock);
>> + if (ticket->bytes == 0) {
>> + spin_unlock(&space_info->lock);
>> + return;
>> + }
>> + spin_unlock(&space_info->lock);
>> + }
>> +again:
>> + while (flush_state < states_nr) {
>> + u64 flush_bytes = U64_MAX;
>> +
>> + if (!commit_cycles) {
>> + if (states[flush_state] == FLUSH_DELALLOC_WAIT) {
>> + flush_state++;
>> + continue;
>> + }
>> + if (states[flush_state] == COMMIT_TRANS)
>> + flush_bytes = ticket->bytes;
>> + }
>> +
>> + flush_space(fs_info, space_info, flush_bytes,
>> + states[flush_state]);
>> + spin_lock(&space_info->lock);
>> + if (ticket->bytes == 0) {
>> + spin_unlock(&space_info->lock);
>> + return;
>> + }
>> + spin_unlock(&space_info->lock);
>> + flush_state++;
>> + }
>> + if (commit_cycles) {
>> + commit_cycles--;
>> + flush_state = 0;
>> + goto again;
>> + }
>> +}
>> +
>> static void wait_reserve_ticket(struct btrfs_fs_info *fs_info,
>> struct btrfs_space_info *space_info,
>> struct reserve_ticket *ticket)
>> @@ -1134,6 +1182,15 @@ static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,
>> evict_flush_states,
>> ARRAY_SIZE(evict_flush_states));
>> break;
>> + case BTRFS_RESERVE_FLUSH_DATA:
>> + priority_reclaim_data_space(fs_info, space_info, ticket,
>> + data_flush_states,
>> + ARRAY_SIZE(data_flush_states));
>> + break;
>> + case BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE:
>> + priority_reclaim_data_space(fs_info, space_info, ticket,
>> + NULL, 0);
>> + break;
>> default:
>> ASSERT(0);
>> break;
>> @@ -1341,78 +1398,30 @@ int btrfs_reserve_data_bytes(struct btrfs_fs_info *fs_info, u64 bytes,
>> enum btrfs_reserve_flush_enum flush)
>> {
>> struct btrfs_space_info *data_sinfo = fs_info->data_sinfo;
>> - const enum btrfs_flush_state *states = NULL;
>> u64 used;
>> - int states_nr = 0;
>> - int commit_cycles = 2;
>> int ret = -ENOSPC;
>>
>> ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_DATA);
>>
>> - if (flush == BTRFS_RESERVE_FLUSH_DATA) {
>> - states = data_flush_states;
>> - states_nr = ARRAY_SIZE(data_flush_states);
>> - }
>> -
>> spin_lock(&data_sinfo->lock);
>> -again:
>> used = btrfs_space_info_used(data_sinfo, true);
>>
>> if (used + bytes > data_sinfo->total_bytes) {
>> - u64 prev_total_bytes = data_sinfo->total_bytes;
>> - int flush_state = 0;
>> + struct reserve_ticket ticket;
>>
>> + init_waitqueue_head(&ticket.wait);
>> + ticket.bytes = bytes;
>> + ticket.error = 0;
>> + list_add_tail(&ticket.list, &data_sinfo->priority_tickets);
>
> nit: Shouldn't adding the ticket also be recorded in
> spac_info->reclaim_size?
> I see later that you are removing this code and relying on the existing
> logic in __reserve_metadata_bytes( renamed to reserve_bytes) which
> correctly modifies reclaim_size, but this just means this particular
> patch is slightly broken.

Yup I'll fix this up, thanks. Thanks,

Josef