[PATCH 14/19] writeback: move over_bground_thresh() to mm/page-writeback.c

Tejun Heo
2015-04-06T20:07:36Z

and rename it to wb_over_bg_thresh(). The function is closely tied to
the dirty throttling mechanism implemented in page-writeback.c. This
relocation will allow future updates necessary for cgroup writeback
support.

While at it, add function comment.

This is pure reorganization and doesn't introduce any behavioral
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>
---
fs/fs-writeback.c | 20 ++------------------
include/linux/writeback.h | 1 +
mm/page-writeback.c | 23 +++++++++++++++++++++++
3 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5b842bd..8c22da2 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1052,22 +1052,6 @@ static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
return nr_pages - work.nr_pages;
}

-static bool over_bground_thresh(struct bdi_writeback *wb)
-{
- unsigned long background_thresh, dirty_thresh;
-
- global_dirty_limits(&background_thresh, &dirty_thresh);
-
- if (global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) > background_thresh)
- return true;
-
- if (wb_stat(wb, WB_RECLAIMABLE) > wb_calc_thresh(wb, background_thresh))
- return true;
-
- return false;
-}
-
/*
* Explicit flushing or periodic writeback of "old" data.
*
@@ -1117,7 +1101,7 @@ static long wb_writeback(struct bdi_writeback *wb,
* For background writeout, stop when we are below the
* background dirty threshold
*/
- if (work->for_background && !over_bground_thresh(wb))
+ if (work->for_background && !wb_over_bg_thresh(wb))
break;

/*
@@ -1208,7 +1192,7 @@ static unsigned long get_nr_dirty_pages(void)

static long wb_check_background_flush(struct bdi_writeback *wb)
{
- if (over_bground_thresh(wb)) {
+ if (wb_over_bg_thresh(wb)) {

struct wb_writeback_work work = {
.nr_pages = LONG_MAX,
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index fe0924a..eb52f23 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -204,6 +204,7 @@ unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);
void page_writeback_init(void);
void balance_dirty_pages_ratelimited(struct address_space *mapping);
+bool wb_over_bg_thresh(struct bdi_writeback *wb);

typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
void *data);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 3d63e39..1bc3a65 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1740,6 +1740,29 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
}
EXPORT_SYMBOL(balance_dirty_pages_ratelimited);

+/**
+ * wb_over_bg_thresh - does @wb need to be written back?
+ * @wb: bdi_writeback of interest
+ *
+ * Determines whether background writeback should keep writing @wb or it's
+ * clean enough. Returns %true if writeback should continue.
+ */
+bool wb_over_bg_thresh(struct bdi_writeback *wb)
+{
+ unsigned long background_thresh, dirty_thresh;
+
+ global_dirty_limits(&background_thresh, &dirty_thresh);
+
+ if (global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS) > background_thresh)
+ return true;
+
+ if (wb_stat(wb, WB_RECLAIMABLE) > wb_calc_thresh(wb, background_thresh))
+ return true;
+
+ return false;
+}
+
void throttle_vm_writeout(gfp_t gfp_mask)
{
unsigned long background_thresh;
--
2.1.0