releases/3.0.1/mm-backing-dev.c-reset-bdi-min_ratio-in-bdi_unregister.patch

   1 From ccb6108f5b0b541d3eb332c3a73e645c0f84278e Mon Sep 17 00:00:00 2001
   2 From: Peter Zijlstra <peterz@infradead.org>
   3 Date: Mon, 25 Jul 2011 17:11:57 -0700
   4 Subject: mm/backing-dev.c: reset bdi min_ratio in bdi_unregister()
   5
   6 From: Peter Zijlstra <peterz@infradead.org>
   7
   8 commit ccb6108f5b0b541d3eb332c3a73e645c0f84278e upstream.
   9
  10 Vito said:
  11
  12 : The system has many usb disks coming and going day to day, with their
  13 : respective bdi's having min_ratio set to 1 when inserted.  It works for
  14 : some time until eventually min_ratio can no longer be set, even when the
  15 : active set of bdi's seen in /sys/class/bdi/*/min_ratio doesn't add up to
  16 : anywhere near 100.
  17 :
  18 : This then leads to an unrelated starvation problem caused by write-heavy
  19 : fuse mounts being used atop the usb disks, a problem the min_ratio setting
  20 : at the underlying devices bdi effectively prevents.
  21
  22 Fix this leakage by resetting the bdi min_ratio when unregistering the
  23 BDI.
  24
  25 Signed-off-by: Peter Zijlstra <peterz@infradead.org>
  26 Reported-by: Vito Caputo <lkml@pengaru.com>
  27 Cc: Wu Fengguang <fengguang.wu@intel.com>
  28 Cc: Miklos Szeredi <miklos@szeredi.hu>
  29 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  30 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  31 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  32
  33 ---
  34  mm/backing-dev.c |    1 +
  35  1 file changed, 1 insertion(+)
  36
  37 --- a/mm/backing-dev.c
  38 +++ b/mm/backing-dev.c
  39 @@ -606,6 +606,7 @@ static void bdi_prune_sb(struct backing_
  40  void bdi_unregister(struct backing_dev_info *bdi)
  41  {
  42         if (bdi->dev) {
  43 +               bdi_set_min_ratio(bdi, 0);
  44                 trace_writeback_bdi_unregister(bdi);
  45                 bdi_prune_sb(bdi);
  46                 del_timer_sync(&bdi->wb.wakeup_timer);