These functions are no longer useful as no BDIs report congestions any
more.

Removing the test on bdi_write_contested() in current_may_throttle()
could cause a small change in behaviour, but only when PF_LOCAL_THROTTLE
is set.

So replace the calls by 'false' and simplify the code - and remove the
functions.

Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com> (for nilfs bits)
Signed-off-by: NeilBrown <redacted>
---
 drivers/block/drbd/drbd_int.h |    3 ---
 drivers/block/drbd/drbd_req.c |    3 +--
 fs/ext2/ialloc.c              |    5 -----
 fs/nilfs2/segbuf.c            |   15 ---------------
 fs/xfs/xfs_buf.c              |    3 ---
 include/linux/backing-dev.h   |   26 --------------------------
 mm/vmscan.c                   |    4 +---
 7 files changed, 2 insertions(+), 57 deletions(-)

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index f27d5b0f9a0b..f804b1bfb3e6 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h

@@ -638,9 +638,6 @@ enum {
        STATE_SENT,             /* Do not change state/UUIDs while this is set */
        CALLBACK_PENDING,       /* Whether we have a call_usermodehelper(, UMH_WAIT_PROC)
                                 * pending, from drbd worker context.
-                                * If set, bdi_write_congested() returns true,
-                                * so shrink_page_list() would not recurse into,
-                                * and potentially deadlock on, this drbd worker.
                                 */
        DISCONNECT_SENT,

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 3235532ae077..2e5fb7e442e3 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c

@@ -909,8 +909,7 @@ static bool remote_due_to_read_balancing(struct drbd_device *device, sector_t se

        switch (rbm) {
        case RB_CONGESTED_REMOTE:
-               return bdi_read_congested(
-                       device->ldev->backing_bdev->bd_disk->bdi);
+               return 0;
        case RB_LEAST_PENDING:
                return atomic_read(&device->local_cnt) >
                        atomic_read(&device->ap_pending_cnt) + atomic_read(&device->rs_pending_cnt);

diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
index df14e750e9fe..998dd2ac8008 100644
--- a/fs/ext2/ialloc.c
+++ b/fs/ext2/ialloc.c

@@ -170,11 +170,6 @@ static void ext2_preread_inode(struct inode *inode)
        unsigned long offset;
        unsigned long block;
        struct ext2_group_desc * gdp;
-       struct backing_dev_info *bdi;
-
-       bdi = inode_to_bdi(inode);
-       if (bdi_rw_congested(bdi))
-               return;

        block_group = (inode->i_ino - 1) / EXT2_INODES_PER_GROUP(inode->i_sb);
        gdp = ext2_get_group_desc(inode->i_sb, block_group, NULL);

diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
index 43287b0d3e9b..c4510f79037f 100644
--- a/fs/nilfs2/segbuf.c
+++ b/fs/nilfs2/segbuf.c

@@ -343,17 +343,6 @@ static int nilfs_segbuf_submit_bio(struct nilfs_segment_buffer *segbuf,
        struct bio *bio = wi->bio;
        int err;

-       if (segbuf->sb_nbio > 0 &&
-           bdi_write_congested(segbuf->sb_super->s_bdi)) {
-               wait_for_completion(&segbuf->sb_bio_event);
-               segbuf->sb_nbio--;
-               if (unlikely(atomic_read(&segbuf->sb_err))) {
-                       bio_put(bio);
-                       err = -EIO;
-                       goto failed;
-               }
-       }
-
        bio->bi_end_io = nilfs_end_bio_write;
        bio->bi_private = segbuf;
        bio_set_op_attrs(bio, mode, mode_flags);

@@ -365,10 +354,6 @@ static int nilfs_segbuf_submit_bio(struct nilfs_segment_buffer *segbuf,
        wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
        wi->start = wi->end;
        return 0;
-
- failed:
-       wi->bio = NULL;
-       return err;
 }

 /**

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index b45e0d50a405..b7ebcfe6b8d3 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c

@@ -843,9 +843,6 @@ xfs_buf_readahead_map(
 {
        struct xfs_buf          *bp;

-       if (bdi_read_congested(target->bt_bdev->bd_disk->bdi))
-               return;
-
        xfs_buf_read_map(target, map, nmaps,
                     XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD, &bp, ops,
                     __this_address);

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 860b675c2929..2d764566280c 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h

@@ -135,11 +135,6 @@ static inline bool writeback_in_progress(struct bdi_writeback *wb)

 struct backing_dev_info *inode_to_bdi(struct inode *inode);

-static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
-{
-       return wb->congested & cong_bits;
-}
-
 long congestion_wait(int sync, long timeout);

 static inline bool mapping_can_writeback(struct address_space *mapping)

@@ -391,27 +386,6 @@ static inline void wb_blkcg_offline(struct blkcg *blkcg)

 #endif /* CONFIG_CGROUP_WRITEBACK */

-static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
-{
-       return wb_congested(&bdi->wb, cong_bits);
-}
-
-static inline int bdi_read_congested(struct backing_dev_info *bdi)
-{
-       return bdi_congested(bdi, 1 << WB_sync_congested);
-}
-
-static inline int bdi_write_congested(struct backing_dev_info *bdi)
-{
-       return bdi_congested(bdi, 1 << WB_async_congested);
-}
-
-static inline int bdi_rw_congested(struct backing_dev_info *bdi)
-{
-       return bdi_congested(bdi, (1 << WB_sync_congested) |
-                                 (1 << WB_async_congested));
-}
-
 const char *bdi_dev_name(struct backing_dev_info *bdi);

 #endif /* _LINUX_BACKING_DEV_H */

diff --git a/mm/vmscan.c b/mm/vmscan.c
index ce8492939bd3..0b930556c4f2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -2362,9 +2362,7 @@ static unsigned int move_pages_to_lru(struct lruvec *lruvec,
  */
 static int current_may_throttle(void)
 {
-       return !(current->flags & PF_LOCAL_THROTTLE) ||
-               current->backing_dev_info == NULL ||
-               bdi_write_congested(current->backing_dev_info);
+       return !(current->flags & PF_LOCAL_THROTTLE);
 }

 /*