diff mbox series

[RFC,v4,03/17] mm: Prepare balance_dirty_pages() for async buffered writes

Message ID 20220520183646.2002023-4-shr@fb.com (mailing list archive)
State New, archived
Headers show
Series io-uring/xfs: support async buffered writes | expand

Commit Message

Stefan Roesch May 20, 2022, 6:36 p.m. UTC 
From: Jan Kara <jack@suse.cz>

If balance_dirty_pages() gets called for async buffered write, we don't
want to wait. Instead we need to indicate to the caller that throttling
is needed so that it can stop writing and offload the rest of the write
to a context that can block.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Stefan Roesch <shr@fb.com>
---
 include/linux/writeback.h |  4 ++++
 mm/page-writeback.c       | 12 +++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

Comments

Christoph Hellwig May 22, 2022, 7:17 a.m. UTC | #1 
On Fri, May 20, 2022 at 11:36:32AM -0700, Stefan Roesch wrote:
> From: Jan Kara <jack@suse.cz>
> 
> If balance_dirty_pages() gets called for async buffered write, we don't
> want to wait. Instead we need to indicate to the caller that throttling
> is needed so that it can stop writing and offload the rest of the write
> to a context that can block.

I don't tink this really makes sense without the next patch, so I'd
suggest to merge the two.
Stefan Roesch May 25, 2022, 9:30 p.m. UTC | #2 
On 5/22/22 12:17 AM, Christoph Hellwig wrote:
> On Fri, May 20, 2022 at 11:36:32AM -0700, Stefan Roesch wrote:
>> From: Jan Kara <jack@suse.cz>
>>
>> If balance_dirty_pages() gets called for async buffered write, we don't
>> want to wait. Instead we need to indicate to the caller that throttling
>> is needed so that it can stop writing and offload the rest of the write
>> to a context that can block.
> 
> I don't tink this really makes sense without the next patch, so I'd
> suggest to merge the two.

I merged the two patches.
diff mbox series

Patch

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index fec248ab1fec..a9114c5090e9 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -372,6 +372,10 @@  void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
 unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
 
 void wb_update_bandwidth(struct bdi_writeback *wb);
+
+/* Invoke balance dirty pages in async mode. */
+#define BDP_ASYNC 0x0001
+
 void balance_dirty_pages_ratelimited(struct address_space *mapping);
 bool wb_over_bg_thresh(struct bdi_writeback *wb);
 
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 89dcc7d8395a..7a320fd2ad33 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1545,8 +1545,8 @@  static inline void wb_dirty_limits(struct dirty_throttle_control *dtc)
  * If we're over `background_thresh' then the writeback threads are woken to
  * perform some writeout.
  */
-static void balance_dirty_pages(struct bdi_writeback *wb,
-				unsigned long pages_dirtied)
+static int balance_dirty_pages(struct bdi_writeback *wb,
+			       unsigned long pages_dirtied, unsigned int flags)
 {
 	struct dirty_throttle_control gdtc_stor = { GDTC_INIT(wb) };
 	struct dirty_throttle_control mdtc_stor = { MDTC_INIT(wb, &gdtc_stor) };
@@ -1566,6 +1566,7 @@  static void balance_dirty_pages(struct bdi_writeback *wb,
 	struct backing_dev_info *bdi = wb->bdi;
 	bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT;
 	unsigned long start_time = jiffies;
+	int ret = 0;
 
 	for (;;) {
 		unsigned long now = jiffies;
@@ -1794,6 +1795,10 @@  static void balance_dirty_pages(struct bdi_writeback *wb,
 					  period,
 					  pause,
 					  start_time);
+		if (flags & BDP_ASYNC) {
+			ret = -EAGAIN;
+			break;
+		}
 		__set_current_state(TASK_KILLABLE);
 		wb->dirty_sleep = now;
 		io_schedule_timeout(pause);
@@ -1825,6 +1830,7 @@  static void balance_dirty_pages(struct bdi_writeback *wb,
 		if (fatal_signal_pending(current))
 			break;
 	}
+	return ret;
 }
 
 static DEFINE_PER_CPU(int, bdp_ratelimits);
@@ -1906,7 +1912,7 @@  void balance_dirty_pages_ratelimited(struct address_space *mapping)
 	preempt_enable();
 
 	if (unlikely(current->nr_dirtied >= ratelimit))
-		balance_dirty_pages(wb, current->nr_dirtied);
+		balance_dirty_pages(wb, current->nr_dirtied, 0);
 
 	wb_put(wb);
 }