[rfc][patch 1/2] mm: rework isolate_lru_page

Nick Piggin
2007-03-05T16:16:55Z

Not suggesting this patch for a merge candidate until a consensus on patch
2 is reached.
--

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.

Signed-off-by: Nick Piggin <npiggin@suse.de>

include/linux/migrate.h | 3 ---
mm/internal.h | 2 ++
mm/mempolicy.c | 10 ++++++++--
mm/migrate.c | 48 ++++++++++--------------------------------------
mm/vmscan.c | 32 ++++++++++++++++++++++++++++++++
5 files changed, 52 insertions(+), 43 deletions(-)

Index: linux-2.6/include/linux/migrate.h
===================================================================
--- linux-2.6.orig/include/linux/migrate.h
+++ linux-2.6/include/linux/migrate.h
@@ -6,7 +6,6 @@
typedef struct page *new_page_t(struct page *, unsigned long private, int **);

#ifdef CONFIG_MIGRATION
-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 *);
@@ -21,8 +20,6 @@ extern int migrate_vmas(struct mm_struct
unsigned long flags);
#else

-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/mm/internal.h
===================================================================
--- linux-2.6.orig/mm/internal.h
+++ linux-2.6/mm/internal.h
@@ -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 fastcall __init __free_pages_bootmem(struct page *page,
unsigned int order);

Index: linux-2.6/mm/migrate.c
===================================================================
--- linux-2.6.orig/mm/migrate.c
+++ linux-2.6/mm/migrate.c
@@ -34,37 +34,6 @@
#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)) {
- ret = 0;
- get_page(page);
- 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().
*/
@@ -806,14 +775,17 @@ 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) {
put_and_set:
- /*
- * Either remove the duplicate refcount from
- * isolate_lru_page() or drop the page ref if it was
- * not isolated.
- */
- put_page(page);
+ /*
+ * Either remove the duplicate refcount from
+ * isolate_lru_page() or drop the page ref if it was
+ * not isolated.
+ */
+ put_page(page);
+ } else
+ list_add_tail(&page->lru, &pagelist);
set_status:
pp->status = err;
}
Index: linux-2.6/mm/vmscan.c
===================================================================
--- linux-2.6.orig/mm/vmscan.c
+++ linux-2.6/mm/vmscan.c
@@ -655,6 +655,38 @@ static unsigned long isolate_lru_pages(u
}

/*
+ * Isolate one page from the LRU lists. Must be called with an elevated
+ * refcount on the page, which is how it differs from isolate_lru_pages
+ * (which is called without a stable reference).
+ *
+ * lru_lock must not be held, interrupts must be enabled.
+ *
+ * Returns:
+ * -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)
+{
+ int ret = -EBUSY;
+
+ if (PageLRU(page)) {
+ struct zone *zone = page_zone(page);
+
+ spin_lock_irq(&zone->lru_lock);
+ if (PageLRU(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/mm/mempolicy.c
===================================================================
--- linux-2.6.orig/mm/mempolicy.c
+++ linux-2.6/mm/mempolicy.c
@@ -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 */
@@ -597,8 +599,12 @@ 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)) {
+ get_page(page);
+ list_add_tail(&page->lru, pagelist);
+ }
+ }
}

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