writeback: remove nonblocking/encountered_congestion references

This removes more dead code that was somehow missed by commit 0d99519efef
(writeback: remove unused nonblocking and congestion checks).  There are
no behavior change except for the removal of two entries from one of the
ext4 tracing interface.

The nonblocking checks in ->writepages are no longer used because the
flusher now prefer to block on get_request_wait() than to skip inodes on
IO congestion.  The latter will lead to more seeky IO.

The nonblocking checks in ->writepage are no longer used because it's
redundant with the WB_SYNC_NONE check.

We no long set ->nonblocking in VM page out and page migration, because
a) it's effectively redundant with WB_SYNC_NONE in current code
b) it's old semantic of "Don't get stuck on request queues" is mis-behavior:
   that would skip some dirty inodes on congestion and page out others, which
   is unfair in terms of LRU age.

Inspired by Christoph Hellwig. Thanks!

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: David Howells <dhowells@redhat.com>
Cc: Sage Weil <sage@newdream.net>
Cc: Steve French <sfrench@samba.org>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 18 deletions

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 722743b152d8..15690bb1d3b5 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -438,7 +438,6 @@ no_more:
  */
 int afs_writepage(struct page *page, struct writeback_control *wbc)
 {
-        struct backing_dev_info *bdi = page->mapping->backing_dev_info;
         struct afs_writeback *wb;
         int ret;
 
@@ -455,8 +454,6 @@ int afs_writepage(struct page *page, struct writeback_control *wbc)
         }
 
         wbc->nr_to_write -= ret;
-        if (wbc->nonblocking && bdi_write_congested(bdi))
-                wbc->encountered_congestion = 1;
 
         _leave(" = 0");
         return 0;
@@ -469,7 +466,6 @@ static int afs_writepages_region(struct address_space *mapping,
                                  struct writeback_control *wbc,
                                  pgoff_t index, pgoff_t end, pgoff_t *_next)
 {
-        struct backing_dev_info *bdi = mapping->backing_dev_info;
         struct afs_writeback *wb;
         struct page *page;
         int ret, n;
@@ -529,11 +525,6 @@ static int afs_writepages_region(struct address_space *mapping,
 
                 wbc->nr_to_write -= ret;
 
-                if (wbc->nonblocking && bdi_write_congested(bdi)) {
-                        wbc->encountered_congestion = 1;
-                        break;
-                }
-
                 cond_resched();
         } while (index < end && wbc->nr_to_write > 0);
 
@@ -548,24 +539,16 @@ static int afs_writepages_region(struct address_space *mapping,
 int afs_writepages(struct address_space *mapping,
                    struct writeback_control *wbc)
 {
-        struct backing_dev_info *bdi = mapping->backing_dev_info;
         pgoff_t start, end, next;
         int ret;
 
         _enter("");
 
-        if (wbc->nonblocking && bdi_write_congested(bdi)) {
-                wbc->encountered_congestion = 1;
-                _leave(" = 0 [congest]");
-                return 0;
-        }
-
         if (wbc->range_cyclic) {
                 start = mapping->writeback_index;
                 end = -1;
                 ret = afs_writepages_region(mapping, wbc, start, end, &next);
-                if (start > 0 && wbc->nr_to_write > 0 && ret == 0 &&
-                    !(wbc->nonblocking && wbc->encountered_congestion))
+                if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
                         ret = afs_writepages_region(mapping, wbc, 0, start,
                                                     &next);
                 mapping->writeback_index = next;