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Re: [dm-devel] commit 6d2a78e783416ba99e36beb1d4395b785b34e867 avoids dm integrity support



On Mon, Mar 30 2009, Martin K. Petersen wrote:
> >>>>> "Kiyoshi" == Kiyoshi Ueda <k-ueda ct jp nec com> writes:
> 
> Kiyoshi> I found this commit (6d2a78e783416ba99e36beb1d4395b785b34e867)
> Kiyoshi> in the recent Linus's git makes every block device share single
> Kiyoshi> mempool for integrity cloning.
> 
> Yeah, until this patch went in I had the integrity stuff hanging off of
> the bio_set to avoid the deadlocks you mention.  When this issue came up
> a few weeks ago Jens suggested the changes in the commit above:
> 
> 	http://marc.info/?l=linux-kernel&m=123662652229483

Well, then suggestions there talk about slab reuse, it still needs
private mempools. The forward progress reference failed to take stacked
drivers into account, I didn't realize that they need to allocate
integrity data again as well. It's a shame, since the commit in question
is otherwise a nice cleanup of the integrity stuff. Apparently the patch
wasn't reviewed well enough, I'll take the blame on that.

> I just talked to him and we're going to back this patch for now.  Short
> term I guess we'll have to settle for a separate pool in the bio_set for
> integrity vectors.

Perhaps it would be cleaner to make the integrity allocation more
explicit in the supported paths, instead of hiding it in bio_set? Dunno,
haven't thought much about it, just an alternative approach

-- 
Jens Axboe


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