Subject: [merged] writeback-fix-negative-bdi-max-pause.patch removed from -mm tree To: fengguang.wu@intel.com,geert@linux-m68k.org,jack@suse.cz,richard@nod.at,stable@vger.kernel.org,toralf.foerster@gmx.de,mm-commits@vger.kernel.org From: akpm@linux-foundation.org Date: Thu, 17 Oct 2013 11:13:23 -0700 The patch titled Subject: writeback: fix negative bdi max pause has been removed from the -mm tree. Its filename was writeback-fix-negative-bdi-max-pause.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Fengguang Wu Subject: 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 Reported-by: Toralf Förster Tested-by: Toralf Förster Reviewed-by: Jan Kara Cc: Richard Weinberger Cc: Geert Uytterhoeven Cc: Signed-off-by: Andrew Morton --- mm/page-writeback.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff -puN mm/page-writeback.c~writeback-fix-negative-bdi-max-pause mm/page-writeback.c --- a/mm/page-writeback.c~writeback-fix-negative-bdi-max-pause +++ a/mm/page-writeback.c @@ -1210,11 +1210,11 @@ static unsigned long dirty_poll_interval 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 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, _ Patches currently in -mm which might be from fengguang.wu@intel.com are origin.patch linux-next.patch smaps-show-vm_softdirty-flag-in-vmflags-line.patch smaps-show-vm_softdirty-flag-in-vmflags-line-fix.patch page-typesc-support-kpf_softdirty-bit.patch writeback-do-not-sync-data-dirtied-after-sync-start.patch writeback-do-not-sync-data-dirtied-after-sync-start-fix.patch writeback-do-not-sync-data-dirtied-after-sync-start-fix-2.patch swap-add-a-simple-detector-for-inappropriate-swapin-readahead.patch swap-add-a-simple-detector-for-inappropriate-swapin-readahead-fix.patch debugging-keep-track-of-page-owners-fix-2-fix-fix-fix.patch debugging-keep-track-of-page-owner-now-depends-on-stacktrace_support.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html