Re: [PATCH 1/2] btrfs: account for pinned bytes and bytes_may_use in should_alloc_chunk

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On 6/14/17 11:44 AM, jeffm@xxxxxxxx wrote:
> From: Jeff Mahoney <jeffm@xxxxxxxx>
> 
> In a heavy write scenario, we can end up with a large number of pinned
> bytes.  This can translate into (very) premature ENOSPC because pinned
> bytes must be accounted for when allowing a reservation but aren't
> accounted for when deciding whether to create a new chunk.
> 
> This patch adds the accounting to should_alloc_chunk so that we can
> create the chunk.
> 
> Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
> ---
>  fs/btrfs/extent-tree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index cb0b924..d027807 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -4389,7 +4389,7 @@ static int should_alloc_chunk(struct btrfs_fs_info *fs_info,
>  {
>  	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
>  	u64 num_bytes = sinfo->total_bytes - sinfo->bytes_readonly;
> -	u64 num_allocated = sinfo->bytes_used + sinfo->bytes_reserved;
> +	u64 num_allocated = sinfo->bytes_used + sinfo->bytes_reserved + sinfo->bytes_pinned + sinfo->bytes_may_use;
>  	u64 thresh;
>  
>  	if (force == CHUNK_ALLOC_FORCE)
> 


Ignore this patch.  It certainly allocates chunks more aggressively, but
it means we end up with a ton of metadata chunks even when we don't have
much metadata.

-Jeff

-- 
Jeff Mahoney
SUSE Labs

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