The patch titled Subject: mm, compaction: prevent VM_BUG_ON when terminating freeing scanner has been added to the -mm tree. Its filename is mm-compaction-prevent-vm_bug_on-when-terminating-freeing-scanner.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-prevent-vm_bug_on-when-terminating-freeing-scanner.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-prevent-vm_bug_on-when-terminating-freeing-scanner.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: David Rientjes <rientjes@xxxxxxxxxx> Subject: mm, compaction: prevent VM_BUG_ON when terminating freeing scanner It's possible to isolate some freepages in a pageblock and then fail split_free_page() due to the low watermark check. In this case, we hit VM_BUG_ON() because the freeing scanner terminated early without a contended lock or enough freepages. This should never have been a VM_BUG_ON() since it's not a fatal condition. It should have been a VM_WARN_ON() at best, or even handled gracefully. Regardless, we need to terminate anytime the full pageblock scan was not done. The logic belongs in isolate_freepages_block(), so handle its state gracefully by terminating the pageblock loop and making a note to restart at the same pageblock next time since it was not possible to complete the scan this time. Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1606291436300.145590@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> Reported-by: Minchan Kim <minchan@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 37 +++++++++++++++---------------------- 1 file changed, 15 insertions(+), 22 deletions(-) diff -puN mm/compaction.c~mm-compaction-prevent-vm_bug_on-when-terminating-freeing-scanner mm/compaction.c --- a/mm/compaction.c~mm-compaction-prevent-vm_bug_on-when-terminating-freeing-scanner +++ a/mm/compaction.c @@ -1009,8 +1009,6 @@ static void isolate_freepages(struct com block_end_pfn = block_start_pfn, block_start_pfn -= pageblock_nr_pages, isolate_start_pfn = block_start_pfn) { - unsigned long isolated; - /* * This can iterate a massively long zone without finding any * suitable migration targets, so periodically check if we need @@ -1034,36 +1032,31 @@ static void isolate_freepages(struct com continue; /* Found a block suitable for isolating free pages from. */ - isolated = isolate_freepages_block(cc, &isolate_start_pfn, - block_end_pfn, freelist, false); - /* If isolation failed early, do not continue needlessly */ - if (!isolated && isolate_start_pfn < block_end_pfn && - cc->nr_migratepages > cc->nr_freepages) - break; + isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn, + freelist, false); /* - * If we isolated enough freepages, or aborted due to async - * compaction being contended, terminate the loop. - * Remember where the free scanner should restart next time, - * which is where isolate_freepages_block() left off. - * But if it scanned the whole pageblock, isolate_start_pfn - * now points at block_end_pfn, which is the start of the next - * pageblock. - * In that case we will however want to restart at the start - * of the previous pageblock. + * If we isolated enough freepages, or aborted due to lock + * contention, terminate. */ if ((cc->nr_freepages >= cc->nr_migratepages) || cc->contended) { - if (isolate_start_pfn >= block_end_pfn) + if (isolate_start_pfn >= block_end_pfn) { + /* + * Restart at previous pageblock if more + * freepages can be isolated next time. + */ isolate_start_pfn = block_start_pfn - pageblock_nr_pages; + } break; - } else { + } else if (isolate_start_pfn < block_end_pfn) { /* - * isolate_freepages_block() should not terminate - * prematurely unless contended, or isolated enough + * If isolation failed early, do not continue + * needlessly. */ - VM_BUG_ON(isolate_start_pfn < block_end_pfn); + isolate_start_pfn = block_start_pfn; + break; } } _ Patches currently in -mm which might be from rientjes@xxxxxxxxxx are mm-compaction-prevent-vm_bug_on-when-terminating-freeing-scanner.patch mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html