On Thu, Jan 19, 2006 at 09:02:26PM +0100, Nick Piggin wrote:
> On Thu, Jan 19, 2006 at 02:52:22PM -0200, Marcelo Tosatti wrote:
> > On Thu, Jan 19, 2006 at 03:50:08PM +0100, Nick Piggin wrote:
> >
> > > The test-set / test-clear operations also kind of imply that it is
> > > being used for locking or without other synchronisation (usually).
> >
> > Non-atomic versions such as __ClearPageLRU()/__ClearPageActive() are
> > not usable, though.
> >
>
> Correct. Although I was able to use them in a couple of other places
> in a subsequent patch in the series. I trust you don't see a problem
> with those usages?
Indeed, sorry. Would you mind adding a comment that page->flags must be
accessed atomically otherwise and that __ versions are special as to
when the page cannot be referenced anymore? (its really not obvious)
Also this comments on top of page-flags.h could be updated
* During disk I/O, PG_locked is used. This bit is set before I/O and
* reset when I/O completes. page_waitqueue(page) is a wait queue of all tasks
* waiting for the I/O on this page to complete.
s/PG_locked/PG_writeback/
* Note that the referenced bit, the page->lru list_head and the active,
* inactive_dirty and inactive_clean lists are protected by the
* zone->lru_lock, and *NOT* by the usual PG_locked bit!
inactive_dirty and inactive_clean do not exist anymore
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