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>

2 files changed, 5 insertions, 5 deletions

diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index 01e9e0076a92..6bcb00645de4 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -242,18 +242,20 @@ TRACE_EVENT(ext4_da_writepages,
                 __entry->pages_skipped  = wbc->pages_skipped;
                 __entry->range_start    = wbc->range_start;
                 __entry->range_end      = wbc->range_end;
-                __entry->nonblocking    = wbc->nonblocking;
                 __entry->for_kupdate    = wbc->for_kupdate;
                 __entry->for_reclaim    = wbc->for_reclaim;
                 __entry->range_cyclic   = wbc->range_cyclic;
                 __entry->writeback_index = inode->i_mapping->writeback_index;
         ),
 
-        TP_printk("dev %s ino %lu nr_to_write %ld pages_skipped %ld range_start %llu range_end %llu nonblocking %d for_kupdate %d for_reclaim %d range_cyclic %d writeback_index %lu",
+        TP_printk("dev %s ino %lu nr_to_write %ld pages_skipped %ld "
+                  "range_start %llu range_end %llu "
+                  "for_kupdate %d for_reclaim %d "
+                  "range_cyclic %d writeback_index %lu",
                   jbd2_dev_to_name(__entry->dev),
                   (unsigned long) __entry->ino, __entry->nr_to_write,
                   __entry->pages_skipped, __entry->range_start,
-                  __entry->range_end, __entry->nonblocking,
+                  __entry->range_end,
                   __entry->for_kupdate, __entry->for_reclaim,
                   __entry->range_cyclic,
                   (unsigned long) __entry->writeback_index)
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index f345f66ae9d1..0bb01ab2e984 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -96,8 +96,6 @@ DECLARE_EVENT_CLASS(wbc_class,
                 __field(long, nr_to_write)
                 __field(long, pages_skipped)
                 __field(int, sync_mode)
-                __field(int, nonblocking)
-                __field(int, encountered_congestion)
                 __field(int, for_kupdate)
                 __field(int, for_background)
                 __field(int, for_reclaim)