writeback: get rid of wbc->for_writepages

It's only set, it's never checked. Kill it.
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/afs/write.c

@@ -712,7 +712,6 @@ int afs_writeback_all(struct afs_vnode *vnode)
 		.bdi		= mapping->backing_dev_info,
 		.sync_mode	= WB_SYNC_ALL,
 		.nr_to_write	= LONG_MAX,
-		.for_writepages = 1,
 		.range_cyclic	= 1,
 	};
 	int ret;

fs/btrfs/ordered-data.c

@@ -740,7 +740,6 @@ int btrfs_fdatawrite_range(struct address_space *mapping, loff_t start,
 		.nr_to_write = mapping->nrpages * 2,
 		.range_start = start,
 		.range_end = end,
-		.for_writepages = 1,
 	};
 	return btrfs_writepages(mapping, &wbc);
 }

fs/jbd2/commit.c

@@ -220,7 +220,6 @@ static int journal_submit_inode_data_buffers(struct address_space *mapping)
 		.nr_to_write = mapping->nrpages * 2,
 		.range_start = 0,
 		.range_end = i_size_read(mapping->host),
-		.for_writepages = 1,
 	};
 
 	ret = generic_writepages(mapping, &wbc);

fs/nfs/write.c

@@ -1490,7 +1490,6 @@ static int nfs_write_mapping(struct address_space *mapping, int how)
 		.nr_to_write = LONG_MAX,
 		.range_start = 0,
 		.range_end = LLONG_MAX,
-		.for_writepages = 1,
 	};
 
 	return __nfs_write_mapping(mapping, &wbc, how);

include/linux/writeback.h

@@ -50,7 +50,6 @@ struct writeback_control {
 	unsigned encountered_congestion:1; /* An output: a queue is full */
 	unsigned for_kupdate:1;		/* A kupdate writeback */
 	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 */
 	/*

include/trace/events/ext4.h

@@ -227,7 +227,6 @@ TRACE_EVENT(ext4_da_writepages,
 		__field(	char,	nonblocking		)
 		__field(	char,	for_kupdate		)
 		__field(	char,	for_reclaim		)
-		__field(	char,	for_writepages		)
 		__field(	char,	range_cyclic		)
 	),
 
@@ -241,16 +240,15 @@ TRACE_EVENT(ext4_da_writepages,
 		__entry->nonblocking	= wbc->nonblocking;
 		__entry->for_kupdate	= wbc->for_kupdate;
 		__entry->for_reclaim	= wbc->for_reclaim;
-		__entry->for_writepages	= wbc->for_writepages;
 		__entry->range_cyclic	= wbc->range_cyclic;
 	),
 
-	TP_printk("dev %s ino %lu nr_t_write %ld pages_skipped %ld range_start %llu range_end %llu nonblocking %d for_kupdate %d for_reclaim %d for_writepages %d range_cyclic %d",
+	TP_printk("dev %s ino %lu nr_t_write %ld pages_skipped %ld range_start %llu range_end %llu nonblocking %d for_kupdate %d for_reclaim %d range_cyclic %d",
 		  jbd2_dev_to_name(__entry->dev), __entry->ino, __entry->nr_to_write,
 		  __entry->pages_skipped, __entry->range_start,
 		  __entry->range_end, __entry->nonblocking,
 		  __entry->for_kupdate, __entry->for_reclaim,
-		  __entry->for_writepages, __entry->range_cyclic)
+		  __entry->range_cyclic)
 );
 
 TRACE_EVENT(ext4_da_writepages_result,

mm/page-writeback.c

@@ -1020,12 +1020,10 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
 
 	if (wbc->nr_to_write <= 0)
 		return 0;
-	wbc->for_writepages = 1;
 	if (mapping->a_ops->writepages)
 		ret = mapping->a_ops->writepages(mapping, wbc);
 	else
 		ret = generic_writepages(mapping, wbc);
-	wbc->for_writepages = 0;
 	return ret;
 }