Messages in this thread | | | Date | Wed, 8 Oct 2003 14:41:13 -0300 (BRT) | From | Marcelo Tosatti <> | Subject | Re: [PATCH] page->flags corruption fix |
| |
On Wed, 8 Oct 2003, Hugh Dickins wrote:
> On Wed, 8 Oct 2003, Rik van Riel wrote: > > > > 1) cpu A adds page P to the swap cache, loading page->flags > > and modifying it locally > > Right, the add_to_swap_cache in try_to_swap_out. > > > 2) a second thread scans a page table entry and sees that > > the page was accessed, so cpu B moves page P to the > > active list > > Right, the mark_page_accessed in try_to_swap_out > (I don't see any other mark_page_accessed as problematic). > Or the del_page_from_active_list in refill_inactive. > > > 3) cpu A undoes the PG_inactive -> PG_active bit change, > > corrupting the page->flags of P > > (Mainline is easier than -rmap since no separate PG_inactive bit.) > > Thanks a lot for explaining, I see it now. Personally I'd prefer a > lighter weight patch, either pagemap_lru_lock within add_to_swap_cache, > or better moving the PG_flags clearing from __add_to_page_cache into > __free_pages_ok, where I still believe it can be done non-atomically. > > But you've proved your point, and I understand you preferring a more > straightforward and future-proof way. I'm not writing an alternative > patch, don't let me stand in the way of progress... > > A little of the above explanation in the change comment would be nice.
Maybe comments on top of the code?
Rik? :)
- 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/
| |