On 22.08.19 г. 22:10 ч., Josef Bacik wrote:
> If we already have tickets on the list we don't want to steal their
> reservations. This is a preparation patch for upcoming changes,
> technically this shouldn't happen today because of the way we add bytes
> to tickets before adding them to the space_info in most cases.
>
> This does not change the FIFO nature of reserve tickets, it simply
> allows us to enforce it in a different way. Previously it was enforced
> because any new space would be added to the first ticket on the list,
> which would result in new reservations getting a reserve ticket. This
> replaces that mechanism by simply checking to see if we have outstanding
> reserve tickets and skipping straight to adding a ticket for our
> reservation.
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
> ---
> fs/btrfs/space-info.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
> index 5f8f65599de1..33fa0ba49759 100644
> --- a/fs/btrfs/space-info.c
> +++ b/fs/btrfs/space-info.c
> @@ -993,6 +993,7 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
> struct reserve_ticket ticket;
> u64 used;
> int ret = 0;
> + bool pending_tickets;
>
> ASSERT(orig_bytes);
> ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_ALL);
> @@ -1000,14 +1001,17 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
> spin_lock(&space_info->lock);
> ret = -ENOSPC;
> used = btrfs_space_info_used(space_info, true);
> + pending_tickets = !list_empty(&space_info->tickets) ||
> + !list_empty(&space_info->priority_tickets);
>
> /*
> * Carry on if we have enough space (short-circuit) OR call
> * can_overcommit() to ensure we can overcommit to continue.
> */
> - if ((used + orig_bytes <= space_info->total_bytes) ||
> - can_overcommit(fs_info, space_info, orig_bytes, flush,
> - system_chunk)) {
> + if (!pending_tickets &&
> + ((used + orig_bytes <= space_info->total_bytes) ||
> + can_overcommit(fs_info, space_info, orig_bytes, flush,
> + system_chunk))) {
> btrfs_space_info_update_bytes_may_use(fs_info, space_info,
> orig_bytes);
> trace_btrfs_space_reservation(fs_info, "space_info",
>
