writeback: relocate wb[_try]_get(), wb_put(), inode_{attach|detach}_wb()

Currently, majority of cgroup writeback support including all the
above functions are implemented in include/linux/backing-dev.h and
mm/backing-dev.c; however, the portion closely related to writeback
logic implemented in include/linux/writeback.h and mm/page-writeback.c
will expand to support foreign writeback detection and correction.

This patch moves wb[_try]_get() and wb_put() to
include/linux/backing-dev-defs.h so that they can be used from
writeback.h and inode_{attach|detach}_wb() to writeback.h and
page-writeback.c.

This is pure reorganization and doesn't introduce any functional
changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 0 insertions, 30 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 84ebf7c..887d72a8 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -660,36 +660,6 @@ struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 	return wb;
 }
 
-void __inode_attach_wb(struct inode *inode, struct page *page)
-{
-	struct backing_dev_info *bdi = inode_to_bdi(inode);
-	struct bdi_writeback *wb = NULL;
-
-	if (inode_cgwb_enabled(inode)) {
-		struct cgroup_subsys_state *memcg_css;
-
-		if (page) {
-			memcg_css = mem_cgroup_css_from_page(page);
-			wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
-		} else {
-			/* must pin memcg_css, see wb_get_create() */
-			memcg_css = task_get_css(current, memory_cgrp_id);
-			wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
-			css_put(memcg_css);
-		}
-	}
-
-	if (!wb)
-		wb = &bdi->wb;
-
-	/*
-	 * There may be multiple instances of this function racing to
-	 * update the same inode.  Use cmpxchg() to tell the winner.
-	 */
-	if (unlikely(cmpxchg(&inode->i_wb, NULL, wb)))
-		wb_put(wb);
-}
-
 static void cgwb_bdi_init(struct backing_dev_info *bdi)
 {
 	bdi->wb.memcg_css = mem_cgroup_root_css;