writeback: skip tmpfs early in balance_dirty_pages_ratelimited_nr()

This helps prevent tmpfs dirtiers from skewing the per-cpu bdp_ratelimits.

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

1 files changed, 4 insertions, 3 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index b2529f8f8be0..1965d05a29cc 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -490,9 +490,6 @@ static void balance_dirty_pages(struct address_space *mapping,
         bool dirty_exceeded = false;
         struct backing_dev_info *bdi = mapping->backing_dev_info;
 
-        if (!bdi_cap_account_dirty(bdi))
-                return;
-
         for (;;) {
                 struct writeback_control wbc = {
                         .sync_mode      = WB_SYNC_NONE,
@@ -631,9 +628,13 @@ static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0;
 void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
                                         unsigned long nr_pages_dirtied)
 {
+        struct backing_dev_info *bdi = mapping->backing_dev_info;
         unsigned long ratelimit;
         unsigned long *p;
 
+        if (!bdi_cap_account_dirty(bdi))
+                return;
+
         ratelimit = ratelimit_pages;
         if (mapping->backing_dev_info->dirty_exceeded)
                 ratelimit = 8;