On Tue, Oct 10, 2017 at 01:31:44PM -0700, Linus Torvalds wrote: > On Tue, Oct 10, 2017 at 12:44 PM, Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > This is all pretty mature code (isn't it?). Any idea why this bug > > popped up now? I have no idea why it's suddenly popped up. It looks like it should be a bohrbug, but it's actually a heisenbug, and I don't understand that either. > Also, while the patch looks sane, the > > clean_buffers(page, PAGE_SIZE); > > line really threw me. That's an insane value to pick, it looks like > "bytes in page", but it isn't. It's just a random value that is bigger > than "PAGE_SIZE >> SECTOR_SHIFT". > > I'd prefer to see just ~0u if the intention is just "bigger than > anything possible". Actually, I did choose it to be "number of bytes in the page", based on the reasoning that I didn't want to calculate what the actual block size was, and the block size surely couldn't be any smaller than one byte. I forgot about the SECTOR_SIZE limit on filesystem block size, so your spelling of "big enough" does look better. Now that I think about it some more, I suppose we might end up with a situation where we're eventually passing a hugepage to this routine, and futureproofing it with ~0U probably makes more sense.
