writeback: implement and use inode_congested()

In several places, bdi_congested() and its wrappers are used to
determine whether more IOs should be issued.  With cgroup writeback
support, this question can't be answered solely based on the bdi
(backing_dev_info).  It's dependent on whether the filesystem and bdi
support cgroup writeback and the blkcg the inode is associated with.

This patch implements inode_congested() and its wrappers which take
@inode and determines the congestion state considering cgroup
writeback.  The new functions replace bdi_*congested() calls in places
where the query is about specific inode and task.

There are several filesystem users which also fit this criteria but
they should be updated when each filesystem implements cgroup
writeback support.

v2: Now that a given inode is associated with only one wb, congestion
    state can be determined independent from the asking task.  Drop
    @task.  Spotted by Vivek.  Also, converted to take @inode instead
    of @mapping and renamed to inode_congested().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 2c498a2a8268..6f0882105f95 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -230,6 +230,7 @@ struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 void __inode_attach_wb(struct inode *inode, struct page *page);
 void wb_memcg_offline(struct mem_cgroup *memcg);
 void wb_blkcg_offline(struct blkcg *blkcg);
+int inode_congested(struct inode *inode, int cong_bits);
 
 /**
  * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
@@ -438,8 +439,29 @@ static inline void wb_blkcg_offline(struct blkcg *blkcg)
 {
 }
 
+static inline int inode_congested(struct inode *inode, int cong_bits)
+{
+	return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
+}
+
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
+static inline int inode_read_congested(struct inode *inode)
+{
+	return inode_congested(inode, 1 << WB_sync_congested);
+}
+
+static inline int inode_write_congested(struct inode *inode)
+{
+	return inode_congested(inode, 1 << WB_async_congested);
+}
+
+static inline int inode_rw_congested(struct inode *inode)
+{
+	return inode_congested(inode, (1 << WB_sync_congested) |
+				      (1 << WB_async_congested));
+}
+
 static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
 {
 	return wb_congested(&bdi->wb, cong_bits);