Messages in this thread |  | | Date | Thu, 20 Sep 2001 09:04:40 +0800 (SGT) | From | Jeff Chua <> | Subject | Re: pre12 VM doubts and patch |
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I still can't find pre12. The latest I've seen is pre11.
Where can I get pre12?
Thanks, Jeff [ jchua@fedex.com ]
On Thu, 20 Sep 2001, Andrea Arcangeli wrote:
> On Wed, Sep 19, 2001 at 04:16:13PM -0700, Linus Torvalds wrote: > > > > On Wed, 19 Sep 2001, Andrea Arcangeli wrote: > > > > > > On Wed, Sep 19, 2001 at 08:42:39PM +0100, Hugh Dickins wrote: > > > > --- 2.4.10-pre12/mm/swap_state.c Wed Sep 19 14:05:54 2001 > > > > +++ linux/mm/swap_state.c Mon Sep 17 06:30:26 2001 > > > > @@ -23,6 +23,17 @@ > > > > */ > > > > static int swap_writepage(struct page *page) > > > > { > > > > + /* One for the page cache, one for this user, one for page->buffers */ > > > > + if (page_count(page) > 2 + !!page->buffers) > > > > > > this is racy, you have to spin_lock(&pagecache_lock) before you can > > > expect the page_count() stays constant. then after you checked the page > > > has count == 1, you must atomically drop it from the pagecache so it's > > > not visible anymore to the swapin lookups. > > > > No. > > > > Note how it is a _heuristic_ only. The "safe" answer is always to say "the > > page is in use", and note that once the page_count has dropped to 2 or > > less, it won't increase unless somebody else has a swap count.. > > the "somebody else has a swap count" is interesting. so we rely on the > fact any swap_duplicate is always run before the swapcache is unlocked. > > Also the "> 2" should be "> 1", but really I noticed I cannot avoid > getting a reference so please apply also this patch instead of replacing > "> 2" with "> 1" (it was a race condition): > > --- 2.4.10pre11aa1/mm/vmscan.c.~1~ Tue Sep 18 21:23:49 2001 > +++ 2.4.10pre11aa1/mm/vmscan.c Thu Sep 20 01:29:58 2001 > @@ -415,7 +415,10 @@ > spin_unlock(&pagemap_lru_lock); > > ClearPageDirty(page); > + > + page_cache_get(page); > writepage(page); > + page_cache_release(page); > > spin_lock(&pagemap_lru_lock); > continue; > > > > And we check for the "somebody else has a swap count" two lines lower. > > I see. > > > Do you see anything wrong with that logic? > > Looks ok now :), I guess it would be good to write a comment now, so > maybe other people won't share my worry, the swap_count thing wasn't > very obvious. thanks, > > Andrea > - > 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/ >
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