Fix congestion_wait() sync/async vs read/write confusion

Commit 1faa16d22877f4839bd433547d770c676d1d964c accidentally broke
the bdi congestion wait queue logic, causing us to wait on congestion
for WRITE (== 1) when we really wanted BLK_RW_ASYNC (== 0) instead.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

5 files changed, 14 insertions, 15 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 493b468a5035..c86edd244294 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -283,7 +283,6 @@ static wait_queue_head_t congestion_wqh[2] = {
                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
         };
 
-
 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 {
         enum bdi_state bit;
@@ -308,18 +307,18 @@ EXPORT_SYMBOL(set_bdi_congested);
 
 /**
  * congestion_wait - wait for a backing_dev to become uncongested
- * @rw: READ or WRITE
+ * @sync: SYNC or ASYNC IO
  * @timeout: timeout in jiffies
  *
  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
  * write congestion.  If no backing_devs are congested then just wait for the
  * next write to be completed.
  */
-long congestion_wait(int rw, long timeout)
+long congestion_wait(int sync, long timeout)
 {
         long ret;
         DEFINE_WAIT(wait);
-        wait_queue_head_t *wqh = &congestion_wqh[rw];
+        wait_queue_head_t *wqh = &congestion_wqh[sync];
 
         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
         ret = io_schedule_timeout(timeout);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e2fa20dadf40..e717964cb5a0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1973,7 +1973,7 @@ try_to_free:
                 if (!progress) {
                         nr_retries--;
                         /* maybe some writeback is necessary */
-                        congestion_wait(WRITE, HZ/10);
+                        congestion_wait(BLK_RW_ASYNC, HZ/10);
                 }
 
         }
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7687879253b9..81627ebcd313 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -575,7 +575,7 @@ static void balance_dirty_pages(struct address_space *mapping)
                 if (pages_written >= write_chunk)
                         break;          /* We've done our duty */
 
-                congestion_wait(WRITE, HZ/10);
+                congestion_wait(BLK_RW_ASYNC, HZ/10);
         }
 
         if (bdi_nr_reclaimable + bdi_nr_writeback < bdi_thresh &&
@@ -669,7 +669,7 @@ void throttle_vm_writeout(gfp_t gfp_mask)
                 if (global_page_state(NR_UNSTABLE_NFS) +
                         global_page_state(NR_WRITEBACK) <= dirty_thresh)
                                 break;
-                congestion_wait(WRITE, HZ/10);
+                congestion_wait(BLK_RW_ASYNC, HZ/10);
 
                 /*
                  * The caller might hold locks which can prevent IO completion
@@ -715,7 +715,7 @@ static void background_writeout(unsigned long _min_pages)
                 if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
                         /* Wrote less than expected */
                         if (wbc.encountered_congestion || wbc.more_io)
-                                congestion_wait(WRITE, HZ/10);
+                                congestion_wait(BLK_RW_ASYNC, HZ/10);
                         else
                                 break;
                 }
@@ -787,7 +787,7 @@ static void wb_kupdate(unsigned long arg)
                 writeback_inodes(&wbc);
                 if (wbc.nr_to_write > 0) {
                         if (wbc.encountered_congestion || wbc.more_io)
-                                congestion_wait(WRITE, HZ/10);
+                                congestion_wait(BLK_RW_ASYNC, HZ/10);
                         else
                                 break;  /* All the old data is written */
                 }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ad7cd1c56b07..a35eeab2724c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1666,7 +1666,7 @@ __alloc_pages_high_priority(gfp_t gfp_mask, unsigned int order,
                         preferred_zone, migratetype);
 
                 if (!page && gfp_mask & __GFP_NOFAIL)
-                        congestion_wait(WRITE, HZ/50);
+                        congestion_wait(BLK_RW_ASYNC, HZ/50);
         } while (!page && (gfp_mask & __GFP_NOFAIL));
 
         return page;
@@ -1831,7 +1831,7 @@ rebalance:
         pages_reclaimed += did_some_progress;
         if (should_alloc_retry(gfp_mask, order, pages_reclaimed)) {
                 /* Wait for some write requests to complete then retry */
-                congestion_wait(WRITE, HZ/50);
+                congestion_wait(BLK_RW_ASYNC, HZ/50);
                 goto rebalance;
         }
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 54155268dfca..dea7abd31098 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1104,7 +1104,7 @@ static unsigned long shrink_inactive_list(unsigned long max_scan,
                  */
                 if (nr_freed < nr_taken && !current_is_kswapd() &&
                     lumpy_reclaim) {
-                        congestion_wait(WRITE, HZ/10);
+                        congestion_wait(BLK_RW_ASYNC, HZ/10);
 
                         /*
                          * The attempt at page out may have made some
@@ -1721,7 +1721,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 
                 /* Take a nap, wait for some writeback to complete */
                 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
-                        congestion_wait(WRITE, HZ/10);
+                        congestion_wait(BLK_RW_ASYNC, HZ/10);
         }
         /* top priority shrink_zones still had more to do? don't OOM, then */
         if (!sc->all_unreclaimable && scanning_global_lru(sc))
@@ -1960,7 +1960,7 @@ loop_again:
                  * another pass across the zones.
                  */
                 if (total_scanned && priority < DEF_PRIORITY - 2)
-                        congestion_wait(WRITE, HZ/10);
+                        congestion_wait(BLK_RW_ASYNC, HZ/10);
 
                 /*
                  * We do this so kswapd doesn't build up large priorities for
@@ -2233,7 +2233,7 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
                                 goto out;
 
                         if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
-                                congestion_wait(WRITE, HZ / 10);
+                                congestion_wait(BLK_RW_ASYNC, HZ / 10);
                 }
         }