synchronous lumpy reclaim: wait for page writeback when directly reclaiming contiguou...

[linux-2.6-omap-h63xx.git] / mm / vmscan.c

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 99ec7fac33e0b09e11900c4b43bcfed56eab3de2..a6e65d024995ad49a1e9675dea9d36b343ceda60 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -271,6 +271,12 @@ static void handle_write_error(struct address_space *mapping,
        unlock_page(page);
 }
 
+/* Request for sync pageout. */
+enum pageout_io {
+       PAGEOUT_IO_ASYNC,
+       PAGEOUT_IO_SYNC,
+};
+
 /* possible outcome of pageout() */
 typedef enum {
        /* failed to write page out, page is locked */
@@ -287,7 +293,8 @@ typedef enum {
  * pageout is called by shrink_page_list() for each dirty page.
  * Calls ->writepage().
  */
-static pageout_t pageout(struct page *page, struct address_space *mapping)
+static pageout_t pageout(struct page *page, struct address_space *mapping,
+                                               enum pageout_io sync_writeback)
 {
        /*
         * If the page is dirty, only perform writeback if that write
@@ -346,6 +353,15 @@ static pageout_t pageout(struct page *page, struct address_space *mapping)
                        ClearPageReclaim(page);
                        return PAGE_ACTIVATE;
                }
+
+               /*
+                * Wait on writeback if requested to. This happens when
+                * direct reclaiming a large contiguous area and the
+                * first attempt to free a range of pages fails.
+                */
+               if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
+                       wait_on_page_writeback(page);
+
                if (!PageWriteback(page)) {
                        /* synchronous write or broken a_ops? */
                        ClearPageReclaim(page);
@@ -423,7 +439,8 @@ cannot_free:
  * shrink_page_list() returns the number of reclaimed pages
  */
 static unsigned long shrink_page_list(struct list_head *page_list,
-                                       struct scan_control *sc)
+                                       struct scan_control *sc,
+                                       enum pageout_io sync_writeback)
 {
        LIST_HEAD(ret_pages);
        struct pagevec freed_pvec;
@@ -458,8 +475,23 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                if (page_mapped(page) || PageSwapCache(page))
                        sc->nr_scanned++;
 
-               if (PageWriteback(page))
-                       goto keep_locked;
+               may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
+                       (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
+
+               if (PageWriteback(page)) {
+                       /*
+                        * Synchronous reclaim is performed in two passes,
+                        * first an asynchronous pass over the list to
+                        * start parallel writeback, and a second synchronous
+                        * pass to wait for the IO to complete.  Wait here
+                        * for any page for which writeback has already
+                        * started.
+                        */
+                       if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
+                               wait_on_page_writeback(page);
+                       else
+                               goto keep_locked;
+               }
 
                referenced = page_referenced(page, 1);
                /* In active use or really unfreeable?  Activate it. */
@@ -478,8 +510,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 #endif /* CONFIG_SWAP */
 
                mapping = page_mapping(page);
-               may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
-                       (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
 
                /*
                 * The page is mapped into the page tables of one or more
@@ -505,7 +535,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                                goto keep_locked;
 
                        /* Page is dirty, try to write it out here */
-                       switch(pageout(page, mapping)) {
+                       switch (pageout(page, mapping, sync_writeback)) {
                        case PAGE_KEEP:
                                goto keep_locked;
                        case PAGE_ACTIVATE:
@@ -786,7 +816,29 @@ static unsigned long shrink_inactive_list(unsigned long max_scan,
                spin_unlock_irq(&zone->lru_lock);
 
                nr_scanned += nr_scan;
-               nr_freed = shrink_page_list(&page_list, sc);
+               nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
+
+               /*
+                * If we are direct reclaiming for contiguous pages and we do
+                * not reclaim everything in the list, try again and wait
+                * for IO to complete. This will stall high-order allocations
+                * but that should be acceptable to the caller
+                */
+               if (nr_freed < nr_taken && !current_is_kswapd() &&
+                                       sc->order > PAGE_ALLOC_COSTLY_ORDER) {
+                       congestion_wait(WRITE, HZ/10);
+
+                       /*
+                        * The attempt at page out may have made some
+                        * of the pages active, mark them inactive again.
+                        */
+                       nr_active = clear_active_flags(&page_list);
+                       count_vm_events(PGDEACTIVATE, nr_active);
+
+                       nr_freed += shrink_page_list(&page_list, sc,
+                                                       PAGEOUT_IO_SYNC);
+               }
+
                nr_reclaimed += nr_freed;
                local_irq_disable();
                if (current_is_kswapd()) {