writeback: avoid unnecessary calculation of bdi dirty thresholds

Split get_dirty_limits() into global_dirty_limits()+bdi_dirty_limit(), so
that the latter can be avoided when under global dirty background
threshold (which is the normal state for most systems).

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 2f76c4a081a2..fca43d4d7bf4 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -590,7 +590,7 @@ static inline bool over_bground_thresh(void)
 {
         unsigned long background_thresh, dirty_thresh;
 
-        get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
+        global_dirty_limits(&background_thresh, &dirty_thresh);
 
         return (global_page_state(NR_FILE_DIRTY) +
                 global_page_state(NR_UNSTABLE_NFS) >= background_thresh);