On Wed, Nov 02, 2022 at 10:35:38AM -0700, Darrick J. Wong wrote: > Just so long as nobody imports that nonfeature of the bufferhead code > where dirtying an already dirty bufferhead skips marking the folio dirty > and writepage failures also fail to redirty the page. That bit us hard > recently and I strongly prefer not to repeat that. Yes, that absolutely needs to be avoided. > > We can always optimize by having a bit for the fairly common all dirty > > case and only track and look at the array if that is no the case. > > Yes, it would help to make the ranges in the bit array better defined > than the semi-opencoded logic there is now. (I'm whining specifically > about the test_bit calls sprinkled around). That is an absolutely requirement. It was so obviosu to me that I didn't bother to restate it after two others already pointed it out :) > Once that's done it > shouldn't be hard to add one more bit for the all-dirty state. Though > I'd want to see the numbers to prove that it saves us time anywhere. We might be able to just use PG_private_2 in the page for now, but maybe just adding a flags field to the iomap_page might be a better idea, as the pageflags tend to have strange entanglements.
