JeffleXu <jefflexu@xxxxxxxxxxxxxxxxx> wrote: > > Fix the dodgy maths in netfs_rreq_unlock_folios(). start_page could be > > inside the folio, in which case the calculation of pgpos will be come up > > with a negative number (though for the moment rreq->start is rounded down > > earlier and folios would have to get merged whilst locked) > > Hi, the patch itself seems fine. Just some questions about the scenario. > > 1. "start_page could be inside the folio" Is that because > .expand_readahead() called from netfs_readahead()? Since otherwise, > req-start is always aligned to the folio boundary. At the moment, rreq->start is always coincident with the start of the first folio in the collection because we always read whole folios - however, it might be best to assume that this might not always hold true if it's simple to fix the maths to get rid of the assumption. > 2. If start_page is indeed inside the folio, then only the trailing part > of the first folio can be covered by the request, and this folio will be > marked with uptodate, though the beginning part of the folio may have > not been read from the cache. Is that expected? Or correct me if I'm wrong. For the moment there's no scenario where this arises; I think we need to wait until we have a scenario and then see how we'll need to juggle the flags. David
