The patch titled
mm/backing-dev.c: reset bdi min_ratio in bdi_unregister()
has been added to the -mm tree. Its filename is
bdi_min_ratio-never-shrinks-ultimately-preventing-valid-setting-of-min_ratio.patch
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------------------------------------------------------
Subject: mm/backing-dev.c: reset bdi min_ratio in bdi_unregister()
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Vito said:
: The system has many usb disks coming and going day to day, with their
: respective bdi's having min_ratio set to 1 when inserted. It works for
: some time until eventually min_ratio can no longer be set, even when the
: active set of bdi's seen in /sys/class/bdi/*/min_ratio doesn't add up to
: anywhere near 100.
:
: This then leads to an unrelated starvation problem caused by write-heavy
: fuse mounts being used atop the usb disks, a problem the min_ratio setting
: at the underlying devices bdi effectively prevents.
Fix this leakage by resetting the bdi min_ratio when unregistering the
BDI.
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Reported-by: Vito Caputo <lkml@xxxxxxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/backing-dev.c | 1 +
1 file changed, 1 insertion(+)
diff -puN mm/backing-dev.c~bdi_min_ratio-never-shrinks-ultimately-preventing-valid-setting-of-min_ratio mm/backing-dev.c
--- a/mm/backing-dev.c~bdi_min_ratio-never-shrinks-ultimately-preventing-valid-setting-of-min_ratio
+++ a/mm/backing-dev.c
@@ -617,6 +617,7 @@ static void bdi_prune_sb(struct backing_
void bdi_unregister(struct backing_dev_info *bdi)
{
if (bdi->dev) {
+ bdi_set_min_ratio(bdi, 0);
trace_writeback_bdi_unregister(bdi);
bdi_prune_sb(bdi);
del_timer_sync(&bdi->wb.wakeup_timer);
_
Patches currently in -mm which might be from peterz@xxxxxxxxxxxxx are
init-calibratec-remove-annoying-printk.patch
linux-next.patch
bdi_min_ratio-never-shrinks-ultimately-preventing-valid-setting-of-min_ratio.patch
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