On 30/06/2020 07:33, Hannes Reinecke wrote:

On 6/29/20 5:32 PM, John Garry wrote:

quoted

Hi all,

I noticed that sbitmap_bitmap_show() only shows set bits and does not 
consider cleared bits. Is that the proper thing to do?

I ask, as from trying to support sbitmap_bitmap_show() for hostwide 
shared tags feature, we currently use blk_mq_queue_tag_busy_iter() to 
find active requests (and associated tags/bits) for a particular hctx. 
So, AFAICT, would give a change in behavior for sbitmap_bitmap_show(), 
in that it would effectively show set and not cleared bits.

Why would you need to do this?
Where would be the point traversing cleared bits?

I'm not talking about traversing cleared bits specifically. I just think 
that today sbitmap_bitmap_show() only showing the bits in 
sbitmap_word.word may not be useful or even misleading, as in reality 
the "set" bits are sbitmap_word.word & ~sbitmap_word.cleared.

And for hostwide shared tags feature, iterating the busy rqs to find the 
per-hctx tags/bits would effectively give us the "set" bits, above, so 
there would be a difference.

Thanks,
John