On Sat, 2007-06-30 at 15:04 +0100, Hugh Dickins wrote: > > Oh yes, the dirty handling is tricky. I had to fix a really nasty bug > > with it lately. As for page_mkclean_one the difference is that it > > doesn't claim a page is dirty if only the write protect bit has not been > > set. If we manage to lose dirty bits from ptes and have to rely on the > > write protect bit to take over the job, then we have a different problem > > altogether, no ? > > [Moving that over from 1/5 discussion]. > > Expect you're right, but I _really_ don't want to comment, when I don't > understand that "|| pte_write" in the first place, and don't know the > consequence of pte_dirty && !pte_write or !pte_dirty && pte_write there.
The pte_write() part is for the shared dirty page tracking. If you want to make sure that a max of x% of your pages are dirty then you cannot allow to have more than x% to be writable. Thats why page_mkclean_one clears the dirty bit and makes the page read-only. > My suspicion is that the "|| pte_write" is precisely to cover your > s390 case where pte is never dirty (it may even have been me who got > Peter to put it in for that reason). In which case your patch would > be fine - though I think it'd be improved a lot by a comment or > rearrangement or new macro in place of the pte_dirty || pte_write > line (perhaps adjust my pte_maybe_dirty in asm-generic/pgtable.h, > and use that - its former use in msync has gone away now). No, s390 is covered by the page_test_dirty / page_clear_dirty pair in page_mkclean. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
