This is a note to let you know that I've just added the patch titled
mm, compaction: prevent VM_BUG_ON when terminating freeing scanner
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-compaction-prevent-vm_bug_on-when-terminating-freeing-scanner.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a46cbf3bc53b6a93fb84a5ffb288c354fa807954 Mon Sep 17 00:00:00 2001
From: David Rientjes <rientjes@xxxxxxxxxx>
Date: Thu, 14 Jul 2016 12:06:50 -0700
Subject: mm, compaction: prevent VM_BUG_ON when terminating freeing scanner
From: David Rientjes <rientjes@xxxxxxxxxx>
commit a46cbf3bc53b6a93fb84a5ffb288c354fa807954 upstream.
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.
[rientjes@xxxxxxxxxx: don't rescan pages in a pageblock]
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1607111244150.83138@xxxxxxxxxxxxxxxxxxxxxxxxx
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>
Tested-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>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 36 ++++++++++++++----------------------
1 file changed, 14 insertions(+), 22 deletions(-)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -964,8 +964,6 @@ 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
@@ -989,36 +987,30 @@ 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);
+ break;
}
}
Patches currently in stable-queue which might be from rientjes@xxxxxxxxxx are
queue-4.4/mm-compaction-abort-free-scanner-if-split-fails.patch
queue-4.4/mm-compaction-prevent-vm_bug_on-when-terminating-freeing-scanner.patch
queue-4.4/mm-meminit-always-return-a-valid-node-from-early_pfn_to_nid.patch
queue-4.4/mm-meminit-ensure-node-is-online-before-checking-whether-pages-are-uninitialised.patch
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