On Tue, Feb 27, 2024 at 05:55:35PM +0100, Pankaj Raghav (Samsung) wrote: > > > > > > > > you guys are both wrong, just use rounddown() > > > > > > Umm, what do you mean just use rounddown? rounddown to ...? > > > > > > We need to get index that are in PAGE units but aligned to min_order > > > pages. > > > > > > The original patch did this: > > > > > > index = mapping_align_start_index(mapping, iocb->ki_pos >> PAGE_SHIFT); > > > > > > Which is essentially a rounddown operation (probably this is what you > > > are suggesting?). > > > > > > So what willy is proposing will do the same. To me, what I proposed is > > > less complicated but to willy it is the other way around. > > > > Ok, I just found the code for mapping_align_start_index() - it is just a > > round_down(). > > > > Never mind; patch looks fine (aside from perhaps some quibbling over > > whether the round_down()) should be done before calling readahead or > > within readahead; I think that might have been more what willy was > > keying in on) > > Yeah, exactly. > > I have one question while I have you here. > > When we have this support in the page cache, do you think bcachefs can make > use of this support to enable bs > ps in bcachefs as it already makes use > of large folios? Yes, of course. > Do you think it is just a simple mapping_set_large_folios -> > mapping_set_folio_min_order(.., block_size order) or it requires more > effort? I think that's all that would be required. There's very little in the way of references to PAGE_SIZE in bcachefs.
