a patch drop request in -mm

[KOSAKI Motohiro <kosaki.motohiro@gmail.com>]

Mel,

Today, my test found following patch makes false-positive warning.
because, truncate can free the pages
although the pages are mlock()ed.

So, I think following patch should be dropped.
.. or, do you think truncate should clear PG_mlock before free the page?

Can I ask your patch intention?


=============================================================
commit 7a06930af46eb39351cbcdc1ab98701259f9a72c
Author: Mel Gorman <mel@csn.ul.ie>
Date:   Tue Aug 25 00:43:07 2009 +0200

    When a page is freed with the PG_mlocked set, it is considered an
    unexpected but recoverable situation.  A counter records how often this
    event happens but it is easy to miss that this event has occured at
    all.  This patch warns once when PG_mlocked is set to prompt debuggers
    to check the counter to see how often it is happening.

    Signed-off-by: Mel Gorman <mel@csn.ul.ie>
    Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
    Acked-by: Johannes Weiner <hannes@cmpxchg.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 28c2f3e..251fd73 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -494,6 +494,11 @@ static inline void __free_one_page(struct page *page,
  */
 static inline void free_page_mlock(struct page *page)
 {
+       WARN_ONCE(1, KERN_WARNING
+               "Page flag mlocked set for process %s at pfn:%05lx\n"
+               "page:%p flags:%#lx\n",
+               current->comm, page_to_pfn(page),
+               page, page->flags|__PG_MLOCKED);
        __dec_zone_page_state(page, NR_MLOCK);
        __count_vm_event(UNEVICTABLE_MLOCKFREED);
 }

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