On 3.12.18 г. 17:24 ч., Josef Bacik wrote:
> For FLUSH_LIMIT flushers (think evict, truncate) we can deadlock when
> running delalloc because we may be holding a tree lock. We can also
> deadlock with delayed refs rsv's that are running via the committing
> mechanism. The only safe operations for FLUSH_LIMIT is to run the
> delayed operations and to allocate chunks, everything else has the
> potential to deadlock. Future proof this by explicitly specifying the
> states that FLUSH_LIMIT is allowed to use. This will keep us from
> introducing bugs later on when adding new flush states.
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
> ---
> fs/btrfs/extent-tree.c | 21 ++++++++++-----------
> 1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 0e1a499035ac..ab9d915d9289 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -5123,12 +5123,18 @@ void btrfs_init_async_reclaim_work(struct work_struct *work)
> INIT_WORK(work, btrfs_async_reclaim_metadata_space);
> }
>
> +static const enum btrfs_flush_state priority_flush_states[] = {
> + FLUSH_DELAYED_ITEMS_NR,
> + FLUSH_DELAYED_ITEMS,
> + ALLOC_CHUNK,
> +};
> +
> static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
> struct btrfs_space_info *space_info,
> struct reserve_ticket *ticket)
> {
> u64 to_reclaim;
> - int flush_state = FLUSH_DELAYED_ITEMS_NR;
> + int flush_state = 0;
>
> spin_lock(&space_info->lock);
> to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info,
> @@ -5140,7 +5146,8 @@ static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
> spin_unlock(&space_info->lock);
>
> do {
> - flush_space(fs_info, space_info, to_reclaim, flush_state);
> + flush_space(fs_info, space_info, to_reclaim,
> + priority_flush_states[flush_state]);
> flush_state++;
> spin_lock(&space_info->lock);
> if (ticket->bytes == 0) {
> @@ -5148,15 +5155,7 @@ static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
> return;
> }
> spin_unlock(&space_info->lock);
> -
> - /*
> - * Priority flushers can't wait on delalloc without
> - * deadlocking.
> - */
> - if (flush_state == FLUSH_DELALLOC ||
> - flush_state == FLUSH_DELALLOC_WAIT)
> - flush_state = ALLOC_CHUNK;
> - } while (flush_state < COMMIT_TRANS);
> + } while (flush_state < ARRAY_SIZE(priority_flush_states));
> }
>
> static int wait_reserve_ticket(struct btrfs_fs_info *fs_info,
>
