Re: [dm-devel] [PATCH 13/14] dm_thin: commit just before processing a pool target info request

[Alasdair G Kergon <agk redhat com>]

On Fri, Mar 16, 2012 at 03:22:36PM +0000, Joe Thornber wrote:
> This makes the free block counts more accurate.
 
I'm not keen on this one: deferring it.

> --- a/drivers/md/dm-thin.c
> +++ b/drivers/md/dm-thin.c
> @@ -2305,6 +2305,15 @@ static int pool_status(struct dm_target *ti, status_type_t type,

(Used by dmsetup status and wait.)

> +		/*
> +		 * If we're in the middle of a transaction the free block
> +		 * counts can be quite out of date, so we do a quick
> +		 * commit.
> +		 */
> +		r = dm_pool_commit_metadata(pool->pmd);
> +		if (r)
> +			return r;
> +

1) If commit fails (repeatedly?) we still need to get the status.

2) Could the commit ever be too slow?  (Or re-use NOFLUSH flag to skip it?)

Alasdair