[patch 2/13] remove pages from the LRU in __free_pages_ok()

[Andrew Morton]

There are some situations where a page's final release is performed by
put_page().  Such as in access_process_vm().  This tends to go BUG()
because the page is on the LRU.

The patch changes __free_pages_ok() to remove the page from the LRU
in this case, as in 2.4.

We need to make changes to this code again later - I have workloads in
which page_cache_release() consumes 5% of CPU resources.  But this
should keep people out of trouble meanwhile.

 page_alloc.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

--- 2.5.29/mm/page_alloc.c~lru-removal	Sat Jul 27 23:38:59 2002
+++ 2.5.29-akpm/mm/page_alloc.c	Sat Jul 27 23:49:03 2002
@@ -89,10 +89,14 @@ static void __free_pages_ok (struct page
 
 	KERNEL_STAT_ADD(pgfree, 1<<order);
 
+	if (PageLRU(page)) {
+		BUG_ON(in_interrupt());		/* It could deadlock */
+		lru_cache_del(page);
+	}
+
 	BUG_ON(PagePrivate(page));
 	BUG_ON(page->mapping != NULL);
 	BUG_ON(PageLocked(page));
-	BUG_ON(PageLRU(page));
 	BUG_ON(PageActive(page));
 	BUG_ON(PageWriteback(page));
 	BUG_ON(page->pte.chain != NULL);
@@ -451,11 +455,8 @@ unsigned long get_zeroed_page(unsigned i
 
 void page_cache_release(struct page *page)
 {
-	if (!PageReserved(page) && put_page_testzero(page)) {
-		if (PageLRU(page))
-			lru_cache_del(page);
+	if (!PageReserved(page) && put_page_testzero(page))
 		__free_pages_ok(page, 0);
-	}
 }
 
 void __free_pages(struct page *page, unsigned int order)

.