Re: [rfc][patch] remove racy sync_page?

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Linus Torvalds wrote:
And I suspect your objection to unplugging is not really about unplugging itself. It's literally about the fact that we use the same page lock for IO and for the ->mapping thing, isn't it? 

Nearly, but not quite that far: it's that we sync_page in lock_page.

I don't think using the single lock for both is too bad (in many
ways they are related eg. you don't want the page to be truncated
while IO is in progress).
IOW, you don't actually dislike plugging itself, you dislike it due to the effects of a totally unrelated locking issue, namely that we use the same lock for two totally independent things. If the ->mapping thing were to use a PG_map_lock that didn't affect plugging one way or the other, you wouldn't have any issues with unplugging, would you?
And I think _that_ is what really gets us to the problem. 

No I don't dislike plugging at all ;) Just this tangle as you say.

--
SUSE Labs, Novell Inc.
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