FS-Cache: Recruit a page flags for cache management

Recruit a page flag to aid in cache management.  The following extra flag is
defined:

 (1) PG_fscache (PG_private_2)

     The marked page is backed by a local cache and is pinning resources in the
     cache driver.

If PG_fscache is set, then things that checked for PG_private will now also
check for that.  This includes things like truncation and page invalidation.
The function page_has_private() had been added to make the checks for both
PG_private and PG_private_2 at the same time.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 06e72693b458..425244988bb2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -283,7 +283,7 @@ static inline int page_mapping_inuse(struct page *page)
 
 static inline int is_page_cache_freeable(struct page *page)
 {
-        return page_count(page) - !!PagePrivate(page) == 2;
+        return page_count(page) - !!page_has_private(page) == 2;
 }
 
 static int may_write_to_queue(struct backing_dev_info *bdi)
@@ -367,7 +367,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping,
                  * Some data journaling orphaned pages can have
                  * page->mapping == NULL while being dirty with clean buffers.
                  */
-                if (PagePrivate(page)) {
+                if (page_has_private(page)) {
                         if (try_to_free_buffers(page)) {
                                 ClearPageDirty(page);
                                 printk("%s: orphaned page\n", __func__);
@@ -727,7 +727,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                  * process address space (page_count == 1) it can be freed.
                  * Otherwise, leave the page on the LRU so it is swappable.
                  */
-                if (PagePrivate(page)) {
+                if (page_has_private(page)) {
                         if (!try_to_release_page(page, sc->gfp_mask))
                                 goto activate_locked;
                         if (!mapping && page_count(page) == 1) {