writeback: fix negative bdi max pause
Toralf runs trinity on UML/i386. After some time it hangs and the last message line is BUG: soft lockup - CPU#0 stuck for 22s! [trinity-child0:1521] It's found that pages_dirtied becomes very large. More than 1000000000 pages in this case: period = HZ * pages_dirtied / task_ratelimit; BUG_ON(pages_dirtied > 2000000000); BUG_ON(pages_dirtied > 1000000000); <--------- UML debug printf shows that we got negative pause here: ick: pause : -984 ick: pages_dirtied : 0 ick: task_ratelimit: 0 pause: + if (pause < 0) { + extern int printf(char *, ...); + printf("ick : pause : %li\n", pause); + printf("ick: pages_dirtied : %lu\n", pages_dirtied); + printf("ick: task_ratelimit: %lu\n", task_ratelimit); + BUG_ON(1); + } trace_balance_dirty_pages(bdi, Since pause is bounded by [min_pause, max_pause] where min_pause is also bounded by max_pause. It's suspected and demonstrated that the max_pause calculation goes wrong: ick: pause : -717 ick: min_pause : -177 ick: max_pause : -717 ick: pages_dirtied : 14 ick: task_ratelimit: 0 The problem lies in the two "long = unsigned long" assignments in bdi_max_pause() which might go negative if the highest bit is 1, and the min_t(long, ...) check failed to protect it falling under 0. Fix all of them by using "unsigned long" throughout the function. Signed-off-by: Fengguang Wu <fengguang.wu@intel.com> Reported-by: Toralf Förster <toralf.foerster@gmx.de> Tested-by: Toralf Förster <toralf.foerster@gmx.de> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Richard Weinberger <richard@nod.at> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
5e9dd373de
commit
e3b6c655b9
|
@ -1210,11 +1210,11 @@ static unsigned long dirty_poll_interval(unsigned long dirty,
|
|||
return 1;
|
||||
}
|
||||
|
||||
static long bdi_max_pause(struct backing_dev_info *bdi,
|
||||
unsigned long bdi_dirty)
|
||||
static unsigned long bdi_max_pause(struct backing_dev_info *bdi,
|
||||
unsigned long bdi_dirty)
|
||||
{
|
||||
long bw = bdi->avg_write_bandwidth;
|
||||
long t;
|
||||
unsigned long bw = bdi->avg_write_bandwidth;
|
||||
unsigned long t;
|
||||
|
||||
/*
|
||||
* Limit pause time for small memory systems. If sleeping for too long
|
||||
|
@ -1226,7 +1226,7 @@ static long bdi_max_pause(struct backing_dev_info *bdi,
|
|||
t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
|
||||
t++;
|
||||
|
||||
return min_t(long, t, MAX_PAUSE);
|
||||
return min_t(unsigned long, t, MAX_PAUSE);
|
||||
}
|
||||
|
||||
static long bdi_min_pause(struct backing_dev_info *bdi,
|
||||
|
|
Loading…
Reference in New Issue