This is a note to let you know that I've just added the patch titled
Revert "mm/compaction: fix set skip in fast_find_migrateblock"
to the 6.1-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:
revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 95e7a450b8190673675836bfef236262ceff084a Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@xxxxxxx>
Date: Fri, 13 Jan 2023 18:33:45 +0100
Subject: Revert "mm/compaction: fix set skip in fast_find_migrateblock"
From: Vlastimil Babka <vbabka@xxxxxxx>
commit 95e7a450b8190673675836bfef236262ceff084a upstream.
This reverts commit 7efc3b7261030da79001c00d92bc3392fd6c664c.
We have got openSUSE reports (Link 1) for 6.1 kernel with khugepaged
stalling CPU for long periods of time. Investigation of tracepoint data
shows that compaction is stuck in repeating fast_find_migrateblock()
based migrate page isolation, and then fails to migrate all isolated
pages.
Commit 7efc3b726103 ("mm/compaction: fix set skip in fast_find_migrateblock")
was suspected as it was merged in 6.1 and in theory can indeed remove a
termination condition for fast_find_migrateblock() under certain
conditions, as it removes a place that always marks a scanned pageblock
from being re-scanned. There are other such places, but those can be
skipped under certain conditions, which seems to match the tracepoint
data.
Testing of revert also appears to have resolved the issue, thus revert
the commit until a more robust solution for the original problem is
developed.
It's also likely this will fix qemu stalls with 6.1 kernel reported in
Link 2, but that is not yet confirmed.
Link: https://bugzilla.suse.com/show_bug.cgi?id=1206848
Link: https://lore.kernel.org/kvm/b8017e09-f336-3035-8344-c549086c2340@xxxxxxxxxx/
Link: https://lore.kernel.org/lkml/20230125134434.18017-1-mgorman@xxxxxxxxxxxxxxxxxxx/
Fixes: 7efc3b726103 ("mm/compaction: fix set skip in fast_find_migrateblock")
Cc: <stable@xxxxxxxxxxxxxxx>
Tested-by: Pedro Falcato <pedro.falcato@xxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/compaction.c b/mm/compaction.c
index ca1603524bbe..8238e83385a7 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1839,6 +1839,7 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc)
pfn = cc->zone->zone_start_pfn;
cc->fast_search_fail = 0;
found_block = true;
+ set_pageblock_skip(freepage);
break;
}
}
--
2.39.1
Patches currently in stable-queue which might be from vbabka@xxxxxxx are
queue-6.1/revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch
