Revert "writeback: introduce writeback_control.more_io to indicate more io"

This reverts commit 2e6883bdf49abd0e7f0d9b6297fc3be7ebb2250b, as
requested by Fengguang Wu.  It's not quite fully baked yet, and while
there are patches around to fix the problems it caused, they should get
more testing.  Says Fengguang: "I'll resend them both for -mm later on,
in a more complete patchset".

See

	http://bugzilla.kernel.org/show_bug.cgi?id=9738

for some of this discussion.

Requested-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/fs-writeback.c

@@ -482,8 +482,6 @@ sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
 		if (wbc->nr_to_write <= 0)
 			break;
 	}
-	if (!list_empty(&sb->s_more_io))
-		wbc->more_io = 1;
 	return;		/* Leave any unwritten inodes on s_io */
 }
 

include/linux/writeback.h

@@ -62,7 +62,6 @@ struct writeback_control {
 	unsigned for_reclaim:1;		/* Invoked from the page allocator */
 	unsigned for_writepages:1;	/* This is a writepages() call */
 	unsigned range_cyclic:1;	/* range_start is cyclic */
-	unsigned more_io:1;		/* more io to be dispatched */
 };
 
 /*

mm/page-writeback.c

@@ -558,7 +558,6 @@ static void background_writeout(unsigned long _min_pages)
 			global_page_state(NR_UNSTABLE_NFS) < background_thresh
 				&& min_pages <= 0)
 			break;
-		wbc.more_io = 0;
 		wbc.encountered_congestion = 0;
 		wbc.nr_to_write = MAX_WRITEBACK_PAGES;
 		wbc.pages_skipped = 0;
@@ -566,9 +565,8 @@ static void background_writeout(unsigned long _min_pages)
 		min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
 		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);
-			else
+			congestion_wait(WRITE, HZ/10);
+			if (!wbc.encountered_congestion)
 				break;
 		}
 	}
@@ -633,12 +631,11 @@ static void wb_kupdate(unsigned long arg)
 			global_page_state(NR_UNSTABLE_NFS) +
 			(inodes_stat.nr_inodes - inodes_stat.nr_unused);
 	while (nr_to_write > 0) {
-		wbc.more_io = 0;
 		wbc.encountered_congestion = 0;
 		wbc.nr_to_write = MAX_WRITEBACK_PAGES;
 		writeback_inodes(&wbc);
 		if (wbc.nr_to_write > 0) {
-			if (wbc.encountered_congestion || wbc.more_io)
+			if (wbc.encountered_congestion)
 				congestion_wait(WRITE, HZ/10);
 			else
 				break;	/* All the old data is written */