The patch titled
Subject: mm/vmscan.c: fix potential deadlock in reclaim_pages()
has been added to the -mm tree. Its filename is
mm-vmscanc-fix-potential-deadlock-in-reclaim_pages.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-vmscanc-fix-potential-deadlock-in-reclaim_pages.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-vmscanc-fix-potential-deadlock-in-reclaim_pages.patch
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------------------------------------------------------
From: Yu Zhao <yuzhao@xxxxxxxxxx>
Subject: mm/vmscan.c: fix potential deadlock in reclaim_pages()
Use memalloc_noreclaim_save()/memalloc_noreclaim_restore() in
reclaim_pages() to prevent the page reclaim from going into the block I/O
layer recursively and deadlock.
Link: https://lkml.kernel.org/r/20210614194727.2684053-1-yuzhao@xxxxxxxxxx
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
--- a/mm/vmscan.c~mm-vmscanc-fix-potential-deadlock-in-reclaim_pages
+++ a/mm/vmscan.c
@@ -1707,6 +1707,7 @@ unsigned int reclaim_clean_pages_from_li
unsigned int nr_reclaimed;
struct page *page, *next;
LIST_HEAD(clean_pages);
+ unsigned int noreclaim_flag;
list_for_each_entry_safe(page, next, page_list, lru) {
if (!PageHuge(page) && page_is_file_lru(page) &&
@@ -1717,8 +1718,17 @@ unsigned int reclaim_clean_pages_from_li
}
}
+ /*
+ * We should be safe here since we are only dealing with file pages and
+ * we are not kswapd and therefore cannot write dirty file pages. But
+ * call memalloc_noreclaim_save() anyway, just in case these conditions
+ * change in the future.
+ */
+ noreclaim_flag = memalloc_noreclaim_save();
nr_reclaimed = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
&stat, true);
+ memalloc_noreclaim_restore(noreclaim_flag);
+
list_splice(&clean_pages, page_list);
mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
-(long)nr_reclaimed);
@@ -2312,6 +2322,7 @@ unsigned long reclaim_pages(struct list_
LIST_HEAD(node_page_list);
struct reclaim_stat dummy_stat;
struct page *page;
+ unsigned int noreclaim_flag;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.priority = DEF_PRIORITY,
@@ -2320,6 +2331,8 @@ unsigned long reclaim_pages(struct list_
.may_swap = 1,
};
+ noreclaim_flag = memalloc_noreclaim_save();
+
while (!list_empty(page_list)) {
page = lru_to_page(page_list);
if (nid == NUMA_NO_NODE) {
@@ -2356,6 +2369,8 @@ unsigned long reclaim_pages(struct list_
}
}
+ memalloc_noreclaim_restore(noreclaim_flag);
+
return nr_reclaimed;
}
_
Patches currently in -mm which might be from yuzhao@xxxxxxxxxx are
mm-vmscanc-fix-potential-deadlock-in-reclaim_pages.patch
