writeback: remove unused nonblocking and congestion checks

- no one is calling wb_writeback and write_cache_pages with
  wbc.nonblocking=1 any more
- lumpy pageout will want to do nonblocking writeback without the
  congestion wait

So remove the congestion checks as suggested by Chris.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Alex Elder <aelder@sgi.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

drivers/staging/pohmelfs/inode.c

@@ -143,7 +143,6 @@ static int pohmelfs_writepages(struct address_space *mapping, struct writeback_c
 	struct inode *inode = mapping->host;
 	struct pohmelfs_inode *pi = POHMELFS_I(inode);
 	struct pohmelfs_sb *psb = POHMELFS_SB(inode->i_sb);
-	struct backing_dev_info *bdi = mapping->backing_dev_info;
 	int err = 0;
 	int done = 0;
 	int nr_pages;
@@ -152,11 +151,6 @@ static int pohmelfs_writepages(struct address_space *mapping, struct writeback_c
 	int scanned = 0;
 	int range_whole = 0;
 
-	if (wbc->nonblocking && bdi_write_congested(bdi)) {
-		wbc->encountered_congestion = 1;
-		return 0;
-	}
-
 	if (wbc->range_cyclic) {
 		index = mapping->writeback_index; /* Start from prev offset */
 		end = -1;
@@ -248,10 +242,6 @@ retry:
 
 			if (wbc->nr_to_write <= 0)
 				done = 1;
-			if (wbc->nonblocking && bdi_write_congested(bdi)) {
-				wbc->encountered_congestion = 1;
-				done = 1;
-			}
 
 			continue;
 out_continue:

fs/fs-writeback.c

@@ -639,14 +639,6 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
 			continue;
 		}
 
-		if (wbc->nonblocking && bdi_write_congested(wb->bdi)) {
-			wbc->encountered_congestion = 1;
-			if (!is_blkdev_sb)
-				break;		/* Skip a congested fs */
-			requeue_io(inode);
-			continue;		/* Skip a congested blockdev */
-		}
-
 		/*
 		 * Was this inode dirtied after sync_sb_inodes was called?
 		 * This keeps sync from extra jobs and livelock.
@@ -770,7 +762,6 @@ static long wb_writeback(struct bdi_writeback *wb,
 			break;
 
 		wbc.more_io = 0;
-		wbc.encountered_congestion = 0;
 		wbc.nr_to_write = MAX_WRITEBACK_PAGES;
 		wbc.pages_skipped = 0;
 		writeback_inodes_wb(wb, &wbc);

fs/xfs/linux-2.6/xfs_aops.c

@@ -904,16 +904,9 @@ xfs_convert_page(
 
 	if (startio) {
 		if (count) {
-			struct backing_dev_info *bdi;
-
-			bdi = inode->i_mapping->backing_dev_info;
 			wbc->nr_to_write--;
-			if (bdi_write_congested(bdi)) {
-				wbc->encountered_congestion = 1;
-				done = 1;
-			} else if (wbc->nr_to_write <= 0) {
+			if (wbc->nr_to_write <= 0)
 				done = 1;
-			}
 		}
 		xfs_start_page_writeback(page, !page_dirty, count);
 	}

mm/page-writeback.c

@@ -821,7 +821,6 @@ int write_cache_pages(struct address_space *mapping,
 		      struct writeback_control *wbc, writepage_t writepage,
 		      void *data)
 {
-	struct backing_dev_info *bdi = mapping->backing_dev_info;
 	int ret = 0;
 	int done = 0;
 	struct pagevec pvec;
@@ -834,11 +833,6 @@ int write_cache_pages(struct address_space *mapping,
 	int range_whole = 0;
 	long nr_to_write = wbc->nr_to_write;
 
-	if (wbc->nonblocking && bdi_write_congested(bdi)) {
-		wbc->encountered_congestion = 1;
-		return 0;
-	}
-
 	pagevec_init(&pvec, 0);
 	if (wbc->range_cyclic) {
 		writeback_index = mapping->writeback_index; /* prev offset */
@@ -957,12 +951,6 @@ continue_unlock:
 					break;
 				}
 			}
-
-			if (wbc->nonblocking && bdi_write_congested(bdi)) {
-				wbc->encountered_congestion = 1;
-				done = 1;
-				break;
-			}
 		}
 		pagevec_release(&pvec);
 		cond_resched();