Re: WARNING: at mm/page-writeback.c:1990 __set_page_dirty_nobuffers+0x13a/0x170()

[Linus Torvalds <torvalds@linux-foundation.org>]

On Fri, Jun 1, 2012 at 9:40 PM, Hugh Dickins <hughd@google.com> wrote:
>
> Move the lock after the loop, I think you meant.

Well, I wasn't sure if anything inside the loop might need it. I don't
*think* so, but at the same time, what protects "page_order(page)"
(or, indeed PageBuddy()) from being stable while that loop content
uses them?

I don't understand that code at all. It does that crazy iteration over
page, and changes "page" in random ways, and then finishes up with a
totally new "page" value that is some random thing that is *after* the
end_page thing. WHAT?

The code makes no sense. It tests all those pages within the
page-block, but then after it has done all those tests, it does the
final

  set_pageblock_migratetype(..)
  move_freepages_block(..)

using a page that is *beyond* the pageblock (and with the whole
page_order() thing, who knows just how far beyond it?)

It looks entirely too much like random-monkey code to me.

            Linus

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>