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Subject[patch 01/14] move isolate_lru_page() to vmscan.c
From: Nick Piggin <npiggin@suse.de>

isolate_lru_page logically belongs to be in vmscan.c than migrate.c.

It is tough, because we don't need that function without memory migration
so there is a valid argument to have it in migrate.c. However a subsequent
patch needs to make use of it in the core mm, so we can happily move it
to vmscan.c.

Also, make the function a little more generic by not requiring that it
adds an isolated page to a given list. Callers can do that.

Note that we now have '__isolate_lru_page()', that does
something quite different, visible outside of vmscan.c
for use with memory controller. Methinks we need to
rationalize these names/purposes. --lts

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

---
V1 -> V2 [lts]:
+ fix botched merge -- add back "get_page_unless_zero()"

From: Nick Piggin <npiggin@suse.de>
To: Linux Memory Management <linux-mm@kvack.org>
Subject: [patch 1/4] mm: move and rework isolate_lru_page
Date: Mon, 12 Mar 2007 07:38:44 +0100 (CET)

Index: linux-2.6.26-rc2-mm1/include/linux/migrate.h
===================================================================
--- linux-2.6.26-rc2-mm1.orig/include/linux/migrate.h 2007-07-08 19:32:17.000000000 -0400
+++ linux-2.6.26-rc2-mm1/include/linux/migrate.h 2008-05-15 16:07:44.000000000 -0400
@@ -25,7 +25,6 @@ static inline int vma_migratable(struct
return 1;
}

-extern int isolate_lru_page(struct page *p, struct list_head *pagelist);
extern int putback_lru_pages(struct list_head *l);
extern int migrate_page(struct address_space *,
struct page *, struct page *);
@@ -42,8 +41,6 @@ extern int migrate_vmas(struct mm_struct
static inline int vma_migratable(struct vm_area_struct *vma)
{ return 0; }

-static inline int isolate_lru_page(struct page *p, struct list_head *list)
- { return -ENOSYS; }
static inline int putback_lru_pages(struct list_head *l) { return 0; }
static inline int migrate_pages(struct list_head *l, new_page_t x,
unsigned long private) { return -ENOSYS; }
Index: linux-2.6.26-rc2-mm1/mm/internal.h
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/internal.h 2008-05-15 11:21:11.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/internal.h 2008-05-15 16:07:44.000000000 -0400
@@ -34,6 +34,8 @@ static inline void __put_page(struct pag
atomic_dec(&page->_count);
}

+extern int isolate_lru_page(struct page *page);
+
extern void __free_pages_bootmem(struct page *page, unsigned int order);

/*
Index: linux-2.6.26-rc2-mm1/mm/migrate.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/migrate.c 2008-05-15 11:21:11.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/migrate.c 2008-05-15 16:07:44.000000000 -0400
@@ -37,36 +37,6 @@
#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))

/*
- * Isolate one page from the LRU lists. If successful put it onto
- * the indicated list with elevated page count.
- *
- * Result:
- * -EBUSY: page not on LRU list
- * 0: page removed from LRU list and added to the specified list.
- */
-int isolate_lru_page(struct page *page, struct list_head *pagelist)
-{
- int ret = -EBUSY;
-
- if (PageLRU(page)) {
- struct zone *zone = page_zone(page);
-
- spin_lock_irq(&zone->lru_lock);
- if (PageLRU(page) && get_page_unless_zero(page)) {
- ret = 0;
- ClearPageLRU(page);
- if (PageActive(page))
- del_page_from_active_list(zone, page);
- else
- del_page_from_inactive_list(zone, page);
- list_add_tail(&page->lru, pagelist);
- }
- spin_unlock_irq(&zone->lru_lock);
- }
- return ret;
-}
-
-/*
* migrate_prep() needs to be called before we start compiling a list of pages
* to be migrated using isolate_lru_page().
*/
@@ -895,7 +865,9 @@ static int do_move_pages(struct mm_struc
!migrate_all)
goto put_and_set;

- err = isolate_lru_page(page, &pagelist);
+ err = isolate_lru_page(page);
+ if (!err)
+ list_add_tail(&page->lru, &pagelist);
put_and_set:
/*
* Either remove the duplicate refcount from
Index: linux-2.6.26-rc2-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/vmscan.c 2008-05-15 11:21:11.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/vmscan.c 2008-05-15 16:07:44.000000000 -0400
@@ -816,6 +816,51 @@ static unsigned long clear_active_flags(
return nr_active;
}

+/**
+ * isolate_lru_page - tries to isolate a page from its LRU list
+ * @page: page to isolate from its LRU list
+ *
+ * Isolates a @page from an LRU list, clears PageLRU and adjusts the
+ * vmstat statistic corresponding to whatever LRU list the page was on.
+ *
+ * Returns 0 if the page was removed from an LRU list.
+ * Returns -EBUSY if the page was not on an LRU list.
+ *
+ * The returned page will have PageLRU() cleared. If it was found on
+ * the active list, it will have PageActive set. That flag may need
+ * to be cleared by the caller before letting the page go.
+ *
+ * The vmstat statistic corresponding to the list on which the page was
+ * found will be decremented.
+ *
+ * Restrictions:
+ * (1) Must be called with an elevated refcount on the page. This is a
+ * fundamentnal difference from isolate_lru_pages (which is called
+ * without a stable reference).
+ * (2) the lru_lock must not be held.
+ * (3) interrupts must be enabled.
+ */
+int isolate_lru_page(struct page *page)
+{
+ int ret = -EBUSY;
+
+ if (PageLRU(page)) {
+ struct zone *zone = page_zone(page);
+
+ spin_lock_irq(&zone->lru_lock);
+ if (PageLRU(page) && get_page_unless_zero(page)) {
+ ret = 0;
+ ClearPageLRU(page);
+ if (PageActive(page))
+ del_page_from_active_list(zone, page);
+ else
+ del_page_from_inactive_list(zone, page);
+ }
+ spin_unlock_irq(&zone->lru_lock);
+ }
+ return ret;
+}
+
/*
* shrink_inactive_list() is a helper for shrink_zone(). It returns the number
* of reclaimed pages
Index: linux-2.6.26-rc2-mm1/mm/mempolicy.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/mempolicy.c 2008-05-15 11:20:57.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/mempolicy.c 2008-05-15 16:07:44.000000000 -0400
@@ -93,6 +93,8 @@
#include <asm/tlbflush.h>
#include <asm/uaccess.h>

+#include "internal.h"
+
/* Internal flags */
#define MPOL_MF_DISCONTIG_OK (MPOL_MF_INTERNAL << 0) /* Skip checks for continuous vmas */
#define MPOL_MF_INVERT (MPOL_MF_INTERNAL << 1) /* Invert check for nodemask */
@@ -758,8 +760,11 @@ static void migrate_page_add(struct page
/*
* Avoid migrating a page that is shared with others.
*/
- if ((flags & MPOL_MF_MOVE_ALL) || page_mapcount(page) == 1)
- isolate_lru_page(page, pagelist);
+ if ((flags & MPOL_MF_MOVE_ALL) || page_mapcount(page) == 1) {
+ if (!isolate_lru_page(page)) {
+ list_add_tail(&page->lru, pagelist);
+ }
+ }
}

static struct page *new_node_page(struct page *page, unsigned long node, int **x)
--
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