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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 09-21-2012, 12:25 AM
Tejun Heo
 
Default bounce: Refactor __blk_queue_bounce to not use bi_io_vec

Hello, Kent.

On Mon, Sep 10, 2012 at 05:22:30PM -0700, Kent Overstreet wrote:
> A bunch of what __blk_queue_bounce() was doing was problematic for the
> immutable bvec work; this cleans that up and the code is quite a bit
> smaller, too.
>
> The __bio_for_each_segment() in copy_to_high_bio_irq() was changed
> because that one's looping over the original bio, not the bounce bio -
> since the bounce code doesn't own that bio the __ version wasn't
> correct.

I do like the new implementation. I think the function is broken
before and after tho. Allocating from fs_bio_set from block layer is
never safe and nothing seems to prevent multiple allocators compete in
the bounce page mempool. This will need a separate bioset and the
multiple mempool allocation would have to be put inside a mutex.

Also, how was this tested?

Thanks.

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tejun

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Old 09-21-2012, 12:27 AM
Tejun Heo
 
Default bounce: Refactor __blk_queue_bounce to not use bi_io_vec

On Mon, Sep 10, 2012 at 05:22:30PM -0700, Kent Overstreet wrote:
> A bunch of what __blk_queue_bounce() was doing was problematic for the
> immutable bvec work; this cleans that up and the code is quite a bit
> smaller, too.
>
> The __bio_for_each_segment() in copy_to_high_bio_irq() was changed
> because that one's looping over the original bio, not the bounce bio -
> since the bounce code doesn't own that bio the __ version wasn't
> correct.

Also, I can't understand the above at all. I can think why it
wouldn't be necessary but why is it wrong because bounce code doesn't
own it?

--
tejun

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