Re: [PATCH 5/8] btrfs: don't enospc all tickets on flush failure

[Nikolay Borisov <nborisov@suse.com>]

On 3.12.18 г. 17:24 ч., Josef Bacik wrote:
> With the introduction of the per-inode block_rsv it became possible to
> have really really large reservation requests made because of data
> fragmentation.  Since the ticket stuff assumed that we'd always have
> relatively small reservation requests it just killed all tickets if we
> were unable to satisfy the current request.  However this is generally
> not the case anymore.  So fix this logic to instead see if we had a
> ticket that we were able to give some reservation to, and if we were
> continue the flushing loop again.  Likewise we make the tickets use the
> space_info_add_old_bytes() method of returning what reservation they did
> receive in hopes that it could satisfy reservations down the line.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>


> ---
>  fs/btrfs/extent-tree.c | 45 +++++++++++++++++++++++++--------------------
>  1 file changed, 25 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 2d0dd70570ca..0ee77a98f867 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -4801,6 +4801,7 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
>  }
>  
>  struct reserve_ticket {
> +	u64 orig_bytes;
>  	u64 bytes;
>  	int error;
>  	struct list_head list;
> @@ -5023,7 +5024,7 @@ static inline int need_do_async_reclaim(struct btrfs_fs_info *fs_info,
>  		!test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
>  }
>  
> -static void wake_all_tickets(struct list_head *head)
> +static bool wake_all_tickets(struct list_head *head)
>  {
>  	struct reserve_ticket *ticket;
>  
> @@ -5032,7 +5033,10 @@ static void wake_all_tickets(struct list_head *head)
>  		list_del_init(&ticket->list);
>  		ticket->error = -ENOSPC;
>  		wake_up(&ticket->wait);
> +		if (ticket->bytes != ticket->orig_bytes)
> +			return true;
>  	}
> +	return false;
>  }
>  
>  /*
> @@ -5100,8 +5104,12 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
>  		if (flush_state > COMMIT_TRANS) {
>  			commit_cycles++;
>  			if (commit_cycles > 2) {
> -				wake_all_tickets(&space_info->tickets);
> -				space_info->flush = 0;
> +				if (wake_all_tickets(&space_info->tickets)) {
> +					flush_state = FLUSH_DELAYED_ITEMS_NR;
> +					commit_cycles--;
> +				} else {
> +					space_info->flush = 0;
> +				}
>  			} else {
>  				flush_state = FLUSH_DELAYED_ITEMS_NR;
>  			}
> @@ -5153,10 +5161,11 @@ static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
>  
>  static int wait_reserve_ticket(struct btrfs_fs_info *fs_info,
>  			       struct btrfs_space_info *space_info,
> -			       struct reserve_ticket *ticket, u64 orig_bytes)
> +			       struct reserve_ticket *ticket)
>  
>  {
>  	DEFINE_WAIT(wait);
> +	u64 reclaim_bytes = 0;
>  	int ret = 0;
>  
>  	spin_lock(&space_info->lock);
> @@ -5177,14 +5186,12 @@ static int wait_reserve_ticket(struct btrfs_fs_info *fs_info,
>  		ret = ticket->error;
>  	if (!list_empty(&ticket->list))
>  		list_del_init(&ticket->list);
> -	if (ticket->bytes && ticket->bytes < orig_bytes) {
> -		u64 num_bytes = orig_bytes - ticket->bytes;
> -		update_bytes_may_use(space_info, -num_bytes);
> -		trace_btrfs_space_reservation(fs_info, "space_info",
> -					      space_info->flags, num_bytes, 0);
> -	}
> +	if (ticket->bytes && ticket->bytes < ticket->orig_bytes)
> +		reclaim_bytes = ticket->orig_bytes - ticket->bytes;
>  	spin_unlock(&space_info->lock);
>  
> +	if (reclaim_bytes)
> +		space_info_add_old_bytes(fs_info, space_info, reclaim_bytes);
>  	return ret;
>  }
>  
> @@ -5210,6 +5217,7 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
>  {
>  	struct reserve_ticket ticket;
>  	u64 used;
> +	u64 reclaim_bytes = 0;
>  	int ret = 0;
>  
>  	ASSERT(orig_bytes);
> @@ -5245,6 +5253,7 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
>  	 * the list and we will do our own flushing further down.
>  	 */
>  	if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
> +		ticket.orig_bytes = orig_bytes;
>  		ticket.bytes = orig_bytes;
>  		ticket.error = 0;
>  		init_waitqueue_head(&ticket.wait);
> @@ -5285,25 +5294,21 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
>  		return ret;
>  
>  	if (flush == BTRFS_RESERVE_FLUSH_ALL)
> -		return wait_reserve_ticket(fs_info, space_info, &ticket,
> -					   orig_bytes);
> +		return wait_reserve_ticket(fs_info, space_info, &ticket);
>  
>  	ret = 0;
>  	priority_reclaim_metadata_space(fs_info, space_info, &ticket);
>  	spin_lock(&space_info->lock);
>  	if (ticket.bytes) {
> -		if (ticket.bytes < orig_bytes) {
> -			u64 num_bytes = orig_bytes - ticket.bytes;
> -			update_bytes_may_use(space_info, -num_bytes);
> -			trace_btrfs_space_reservation(fs_info, "space_info",
> -						      space_info->flags,
> -						      num_bytes, 0);
> -
> -		}
> +		if (ticket.bytes < orig_bytes)
> +			reclaim_bytes = orig_bytes - ticket.bytes;
>  		list_del_init(&ticket.list);
>  		ret = -ENOSPC;
>  	}
>  	spin_unlock(&space_info->lock);
> +
> +	if (reclaim_bytes)
> +		space_info_add_old_bytes(fs_info, space_info, reclaim_bytes);
>  	ASSERT(list_empty(&ticket.list));
>  	return ret;
>  }
>