Fix lots of crashes under compaction load: isolate_migratepages_block()
must clean up appropriately when rejecting a page, setting PageLRU again
if it had been cleared; and a put_page() after get_page_unless_zero()
cannot safely be done while holding locked_lruvec - it may turn out to
be the final put_page(), which will take an lruvec lock when PageLRU.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
These fixes should be folded into 10/16 and 12/16,
I have not tried to figure out what belongs in which.
mm/compaction.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
--- alexv12/mm/compaction.c 2020-06-11 13:24:52.037154793 -0700
+++ hughd/mm/compaction.c 2020-06-11 13:48:10.437046025 -0700
@@ -879,6 +879,7 @@ isolate_migratepages_block(struct compac
if (!valid_page && IS_ALIGNED(low_pfn, pageblock_nr_pages)) {
if (!cc->ignore_skip_hint && get_pageblock_skip(page)) {
low_pfn = end_pfn;
+ page = NULL;
goto isolate_abort;
}
valid_page = page;
@@ -971,10 +972,8 @@ isolate_migratepages_block(struct compac
goto isolate_fail;
/* Try isolate the page */
- if (!TestClearPageLRU(page)) {
- put_page(page);
- goto isolate_fail;
- }
+ if (!TestClearPageLRU(page))
+ goto isolate_fail_put;
rcu_read_lock();
lruvec = mem_cgroup_page_lruvec(page, pgdat);
@@ -1005,7 +1004,8 @@ isolate_migratepages_block(struct compac
*/
if (unlikely(PageCompound(page) && !cc->alloc_contig)) {
low_pfn += compound_nr(page) - 1;
- goto isolate_fail;
+ SetPageLRU(page);
+ goto isolate_fail_put;
}
} else
rcu_read_unlock();
@@ -1038,6 +1038,15 @@ isolate_success:
}
continue;
+
+isolate_fail_put:
+ /* Avoid potential deadlock in freeing page under lru_lock */
+ if (locked_lruvec) {
+ unlock_page_lruvec_irqrestore(locked_lruvec, flags);
+ locked_lruvec = NULL;
+ }
+ put_page(page);
+
isolate_fail:
if (!skip_on_failure)
continue;
@@ -1074,10 +1083,15 @@ isolate_fail:
*/
if (unlikely(low_pfn > end_pfn))
low_pfn = end_pfn;
+ page = NULL;
isolate_abort:
if (locked_lruvec)
unlock_page_lruvec_irqrestore(locked_lruvec, flags);
+ if (page) {
+ SetPageLRU(page);
+ put_page(page);
+ }
/*
* Updated the cached scanner pfn once the pageblock has been scanned
