writeback: consolidate variable names in balance_dirty_pages()

Introduce

	nr_dirty = NR_FILE_DIRTY + NR_WRITEBACK + NR_UNSTABLE_NFS

in order to simplify many tests in the following patches.

balance_dirty_pages() will eventually care only about the dirty sums
besides nr_writeback.

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 446bdf7b975b113220f1c9b1666fe4b1cf2296ee..5f3e1b46ace5820b24261f261ee8a6cd5e6155cc 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -565,8 +565,9 @@ static void bdi_update_bandwidth(struct backing_dev_info *bdi,
 static void balance_dirty_pages(struct address_space *mapping,
                                unsigned long write_chunk)
 {
-       long nr_reclaimable, bdi_nr_reclaimable;
-       long nr_writeback, bdi_nr_writeback;
+       unsigned long nr_reclaimable, bdi_nr_reclaimable;
+       unsigned long nr_dirty;  /* = file_dirty + writeback + unstable_nfs */
+       unsigned long bdi_dirty;
        unsigned long background_thresh;
        unsigned long dirty_thresh;
        unsigned long bdi_thresh;
@@ -579,7 +580,7 @@ static void balance_dirty_pages(struct address_space *mapping,
        for (;;) {
                nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
                                        global_page_state(NR_UNSTABLE_NFS);
-               nr_writeback = global_page_state(NR_WRITEBACK);
+               nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
 
                global_dirty_limits(&background_thresh, &dirty_thresh);
 
@@ -588,8 +589,7 @@ static void balance_dirty_pages(struct address_space *mapping,
                 * catch-up. This avoids (excessively) small writeouts
                 * when the bdi limits are ramping up.
                 */
-               if (nr_reclaimable + nr_writeback <=
-                               (background_thresh + dirty_thresh) / 2)
+               if (nr_dirty <= (background_thresh + dirty_thresh) / 2)
                        break;
 
                bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
@@ -607,10 +607,12 @@ static void balance_dirty_pages(struct address_space *mapping,
                 */
                if (bdi_thresh < 2*bdi_stat_error(bdi)) {
                        bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
-                       bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
+                       bdi_dirty = bdi_nr_reclaimable +
+                                   bdi_stat_sum(bdi, BDI_WRITEBACK);
                } else {
                        bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
-                       bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
+                       bdi_dirty = bdi_nr_reclaimable +
+                                   bdi_stat(bdi, BDI_WRITEBACK);
                }
 
                /*
@@ -619,9 +621,8 @@ static void balance_dirty_pages(struct address_space *mapping,
                 * bdi or process from holding back light ones; The latter is
                 * the last resort safeguard.
                 */
-               dirty_exceeded =
-                       (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
-                       || (nr_reclaimable + nr_writeback > dirty_thresh);
+               dirty_exceeded = (bdi_dirty > bdi_thresh) ||
+                                 (nr_dirty > dirty_thresh);
 
                if (!dirty_exceeded)
                        break;