94 lines
3.0 KiB
Diff
94 lines
3.0 KiB
Diff
From e3b6c655b91e01a1dade056cfa358581b47a5351 Mon Sep 17 00:00:00 2001
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From: Fengguang Wu <fengguang.wu@intel.com>
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Date: Wed, 16 Oct 2013 13:47:03 -0700
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Subject: writeback: fix negative bdi max pause
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From: Fengguang Wu <fengguang.wu@intel.com>
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commit e3b6c655b91e01a1dade056cfa358581b47a5351 upstream.
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Toralf runs trinity on UML/i386. After some time it hangs and the last
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message line is
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BUG: soft lockup - CPU#0 stuck for 22s! [trinity-child0:1521]
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It's found that pages_dirtied becomes very large. More than 1000000000
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pages in this case:
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period = HZ * pages_dirtied / task_ratelimit;
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BUG_ON(pages_dirtied > 2000000000);
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BUG_ON(pages_dirtied > 1000000000); <---------
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UML debug printf shows that we got negative pause here:
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ick: pause : -984
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ick: pages_dirtied : 0
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ick: task_ratelimit: 0
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pause:
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+ if (pause < 0) {
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+ extern int printf(char *, ...);
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+ printf("ick : pause : %li\n", pause);
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+ printf("ick: pages_dirtied : %lu\n", pages_dirtied);
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+ printf("ick: task_ratelimit: %lu\n", task_ratelimit);
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+ BUG_ON(1);
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+ }
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trace_balance_dirty_pages(bdi,
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Since pause is bounded by [min_pause, max_pause] where min_pause is also
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bounded by max_pause. It's suspected and demonstrated that the
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max_pause calculation goes wrong:
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ick: pause : -717
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ick: min_pause : -177
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ick: max_pause : -717
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ick: pages_dirtied : 14
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ick: task_ratelimit: 0
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The problem lies in the two "long = unsigned long" assignments in
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bdi_max_pause() which might go negative if the highest bit is 1, and the
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min_t(long, ...) check failed to protect it falling under 0. Fix all of
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them by using "unsigned long" throughout the function.
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Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
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Reported-by: Toralf Förster <toralf.foerster@gmx.de>
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Tested-by: Toralf Förster <toralf.foerster@gmx.de>
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Reviewed-by: Jan Kara <jack@suse.cz>
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Cc: Richard Weinberger <richard@nod.at>
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Cc: Geert Uytterhoeven <geert@linux-m68k.org>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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mm/page-writeback.c | 10 +++++-----
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1 file changed, 5 insertions(+), 5 deletions(-)
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--- a/mm/page-writeback.c
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+++ b/mm/page-writeback.c
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@@ -1104,11 +1104,11 @@ static unsigned long dirty_poll_interval
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return 1;
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}
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-static long bdi_max_pause(struct backing_dev_info *bdi,
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- unsigned long bdi_dirty)
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+static unsigned long bdi_max_pause(struct backing_dev_info *bdi,
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+ unsigned long bdi_dirty)
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{
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- long bw = bdi->avg_write_bandwidth;
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- long t;
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+ unsigned long bw = bdi->avg_write_bandwidth;
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+ unsigned long t;
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/*
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* Limit pause time for small memory systems. If sleeping for too long
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@@ -1120,7 +1120,7 @@ static long bdi_max_pause(struct backing
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t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
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t++;
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- return min_t(long, t, MAX_PAUSE);
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+ return min_t(unsigned long, t, MAX_PAUSE);
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}
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static long bdi_min_pause(struct backing_dev_info *bdi,
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