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Date: Mon, 20 Dec 2010 12:31:55 +0900 From: Minchan Kim <minchan.kim@...il.com> To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Nick Piggin <npiggin@...e.de>, Al Viro <viro@...iv.linux.org.uk>, Andi Kleen <andi@...stfloor.org> Subject: Re: [RFC 5/5] truncate: Remove unnecessary page release On Mon, Dec 20, 2010 at 12:03 PM, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote: >> On Mon, Dec 20, 2010 at 11:32 AM, KOSAKI Motohiro >> <kosaki.motohiro@...fujitsu.com> wrote: >> >> On Mon, Dec 20, 2010 at 11:21 AM, KOSAKI Motohiro >> >> <kosaki.motohiro@...fujitsu.com> wrote: >> >> >> This patch series changes remove_from_page_cache's page ref counting >> >> >> rule. page cache ref count is decreased in remove_from_page_cache. >> >> >> So we don't need call again in caller context. >> >> >> >> >> >> Cc: Nick Piggin <npiggin@...e.de> >> >> >> Cc: Al Viro <viro@...iv.linux.org.uk> >> >> >> Cc: linux-mm@...ck.org >> >> >> Signed-off-by: Minchan Kim <minchan.kim@...il.com> >> >> >> --- >> >> >> mm/truncate.c | 1 - >> >> >> 1 files changed, 0 insertions(+), 1 deletions(-) >> >> >> >> >> >> diff --git a/mm/truncate.c b/mm/truncate.c >> >> >> index 9ee5673..8decb93 100644 >> >> >> --- a/mm/truncate.c >> >> >> +++ b/mm/truncate.c >> >> >> @@ -114,7 +114,6 @@ truncate_complete_page(struct address_space *mapping, struct page *page) >> >> >> * calls cleancache_put_page (and note page->mapping is now NULL) >> >> >> */ >> >> >> cleancache_flush_page(mapping, page); >> >> >> - page_cache_release(page); /* pagecache ref */ >> >> >> return 0; >> >> > >> >> > Do we _always_ have stable page reference here? IOW, I can assume >> >> >> >> I think so. >> >> Because the page is locked so caller have to hold a ref to unlock it. >> > >> > Hmm... >> > >> > Perhaps, I'm missing something. But I think __memory_failure() only lock >> > compaund_head page. not all. example. >> >> The page passed truncate_complete_page is only head page? >> Is it possible to pass the page which isn't head of compound in >> truncate_complete_page? > > I dunno, really. My five miniture grep found following logic. therefore I asked you. > > > > __memory_failure() > { > p = pfn_to_page(pfn); > hpage = compound_head(p); > (snip) > res = -EBUSY; > for (ps = error_states;; ps++) { > if ((p->flags & ps->mask) == ps->res) { > res = page_action(ps, p, pfn); // call truncate here > break; > } > } > out: > unlock_page(hpage); > } > > AFAIK, We have to handle head page when we handle compound page. Internal page handling logic about tail pages is hidden by compound page internal. So I think memory_failure also don't have a problem. For needing double check, Cced Andi. Thanks for the review, KOSAKI. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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