Daniel Phillips wrote:
>
> ...
> /*
> * We must not allow an anon page
> * with no buffers to be visible on
> * the LRU, so we unlock the page after
> * taking the lru lock
> */
>
> That is, what's scary about an anon page without buffers?
ooop. That's an akpm comment. umm, err..
It solves this BUG:
http://www.cs.helsinki.fi/linux/linux-kernel/2001-37/0594.html
Around the 2.4.10 timeframe, Andrea started putting anon pages
on the LRU. Then he backed that out, then put it in again. I
think this comment dates from the time when anon pages were
not on the LRU. So there's a little window there where the
page is unlocked, we've just dropped its swapdev buffers, the page is
on the LRU and pagemap_lru_lock is not held.
So another CPU came in, found the page on the LRU, saw that it had
no ->mapping and no ->buffers and went BUG.
The fix was to take pagemap_lru_lock before unlocking the page.
The comment is stale.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sat Sep 07 2002 - 22:00:24 EST