The patch titled
Subject: mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start-fix
has been added to the -mm mm-unstable branch. Its filename is
mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start-fix.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start-fix
Date: Fri, 2 Jun 2023 12:16:22 +0100
Vlastimil Babka pointed out the following problem with
mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start.patch
I wonder if this has an unintended side-effect that if we resume
isolate_migratepages_block() of a partially compacted pageblock
to finish it, test_and_set_skip() will now tell us to abort,
because we already set the skip bit in the previous call. This
would include the cc->finish_pageblock rescan cases.
He is correct and a partial rescan as implemented in "mm, compaction:
finish pageblocks on complete migration failure" would abort prematurely.
Test and set the skip bit when acquiring "exclusive access" to a pageblock
for migration but only abort if the calling context is not rescanning to
finish a pageblock.
This is a fix for the mmotm patch
mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start.patch
Link: https://lkml.kernel.org/r/20230602111622.swtxhn6lu2qwgrwq@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>
Cc: Jiri Slaby <jirislaby@xxxxxxxxxx>
Cc: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Pedro Falcato <pedro.falcato@xxxxxxxxx>
Cc: Raghavendra K T <raghavendra.kt@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
--- a/mm/compaction.c~mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start-fix
+++ a/mm/compaction.c
@@ -1069,11 +1069,17 @@ isolate_migratepages_block(struct compac
lruvec_memcg_debug(lruvec, page_folio(page));
- /* Try get exclusive access under lock */
+ /*
+ * Try get exclusive access under lock. If marked for
+ * skip, the scan is aborted unless the current context
+ * is a rescan to reach the end of the pageblock.
+ */
if (!skip_updated && valid_page) {
skip_updated = true;
- if (test_and_set_skip(cc, valid_page))
+ if (test_and_set_skip(cc, valid_page) &&
+ !cc->finish_pageblock) {
goto isolate_abort;
+ }
}
/*
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-compaction-ensure-rescanning-only-happens-on-partially-scanned-pageblocks.patch
mm-compaction-only-force-pageblock-scan-completion-when-skip-hints-are-obeyed.patch
mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start.patch
mm-compaction-update-pageblock-skip-when-first-migration-candidate-is-not-at-the-start-fix.patch
revert-revert-mm-compaction-fix-set-skip-in-fast_find_migrateblock.patch
