Currently, balance_dirty_pages() always work on bdi->wb. This patch
updates it to work on the cgwb (cgroup bdi_writeback) matching the
blkcg of the current task as that's what the pages are being dirtied
against.
balance_dirty_pages_ratelimited() now pins the current blkcg and looks
up the matching cgwb and passes it to balance_dirty_pages(). The
pinning is necessary to ensure that the cgwb stays alive while the
function is executing as a cgwb's lifetime is determined by its bdi
and blkcg.
As no filesystem has FS_CGROUP_WRITEBACK yet, this doesn't lead to
visible behavior differences.
Signed-off-by: Tejun Heo <t...@kernel.org>
Cc: Jens Axboe <ax...@kernel.dk>
Cc: Jan Kara <j...@suse.cz>
---
mm/page-writeback.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index d1fea3a..b115a57 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1335,6 +1335,7 @@ static inline void wb_dirty_limits(struct bdi_writeback
*wb,
* perform some writeout.
*/
static void balance_dirty_pages(struct address_space *mapping,
+ struct bdi_writeback *wb,
unsigned long pages_dirtied)
{
unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */
@@ -1351,7 +1352,6 @@ static void balance_dirty_pages(struct address_space
*mapping,
unsigned long dirty_ratelimit;
unsigned long pos_ratio;
struct backing_dev_info *bdi = mapping->backing_dev_info;
- struct bdi_writeback *wb = &bdi->wb;
bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT;
unsigned long start_time = jiffies;
@@ -1575,13 +1575,25 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
void balance_dirty_pages_ratelimited(struct address_space *mapping)
{
struct backing_dev_info *bdi = mapping->backing_dev_info;
- struct bdi_writeback *wb = &bdi->wb;
+ struct cgroup_subsys_state *blkcg_css = NULL;
+ struct bdi_writeback *wb = NULL;
int ratelimit;
int *p;
if (!bdi_cap_account_dirty(bdi))
return;
+ /*
+ * Throttle against the cgwb of the current blkcg. Make sure that
+ * the cgwb stays alive by pinning the blkcg.
+ */
+ if (mapping_cgwb_enabled(mapping)) {
+ blkcg_css = task_get_blkcg_css(current);
+ wb = cgwb_lookup(bdi, blkcg_css);
+ }
+ if (!wb)
+ wb = &bdi->wb;
+
ratelimit = current->nr_dirtied_pause;
if (wb->dirty_exceeded)
ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));
@@ -1615,7 +1627,10 @@ void balance_dirty_pages_ratelimited(struct
address_space *mapping)
preempt_enable();
if (unlikely(current->nr_dirtied >= ratelimit))
- balance_dirty_pages(mapping, current->nr_dirtied);
+ balance_dirty_pages(mapping, wb, current->nr_dirtied);
+
+ if (blkcg_css)
+ css_put(blkcg_css);
}
EXPORT_SYMBOL(balance_dirty_pages_ratelimited);
--
2.1.0
--
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