Re: [PATCH 06/35] btrfs: check if free bgs for commit

Nikolay Borisov
2018-09-03T13:25:45Z

On 30.08.2018 20:41, Josef Bacik wrote:
> may_commit_transaction will skip committing the transaction if we don't
> have enough pinned space or if we're trying to find space for a SYSTEM
> chunk. However if we have pending free block groups in this transaction
> we still want to commit as we may be able to allocate a chunk to make
> our reservation. So instead of just returning ENOSPC, check if we have
> free block groups pending, and if so commit the transaction to allow us
> to use that free space.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
> fs/btrfs/extent-tree.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 6e7f350754d2..80615a579b18 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -4804,6 +4804,7 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
> struct btrfs_trans_handle *trans;
> u64 bytes;
> u64 reclaim_bytes = 0;
> + bool do_commit = true;
>
> trans = (struct btrfs_trans_handle *)current->journal_info;
> if (trans)

While you are at it, does this check even make sense, since the
transaction handle is acquired proper later I think this can be removed?

> @@ -4832,8 +4833,10 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
> * See if there is some space in the delayed insertion reservation for
> * this reservation.
> */
> - if (space_info != delayed_rsv->space_info)
> - return -ENOSPC;
> + if (space_info != delayed_rsv->space_info) {
> + do_commit = false;
> + goto commit;
> + }
>
> spin_lock(&delayed_rsv->lock);
> reclaim_bytes += delayed_rsv->reserved;
> @@ -4848,15 +4851,18 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
>
> if (__percpu_counter_compare(&space_info->total_bytes_pinned,
> bytes,
> - BTRFS_TOTAL_BYTES_PINNED_BATCH) < 0) {
> - return -ENOSPC;
> - }
> -
> + BTRFS_TOTAL_BYTES_PINNED_BATCH) < 0)
> + do_commit = false;
> commit:
> trans = btrfs_join_transaction(fs_info->extent_root);
> if (IS_ERR(trans))
> return -ENOSPC;
>
> + if (!do_commit &&> + !test_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags)) {
> + btrfs_end_transaction(trans);
> + return -ENOSPC;
> + }
> return btrfs_commit_transaction(trans);
> }
>
>