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Date:   Fri, 13 Jan 2023 15:50:45 +0800 (CST)
Message-ID: <202301131550455361823@zte.com.cn>
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From:   <yang.yang29@zte.com.cn>
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Cc:     <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
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From: Yang Yang <yang.yang29@zte.com.cn>

Shadow_nodes is for shadow nodes reclaiming of workingset handling,
it is updated when page cache add or delete since long time ago
workingset only supported page cache. But when workingset supports
anonymous page detection, we missied updating shadow nodes for
it. This caused that shadow nodes of anonymous page will never be
reclaimd by scan_shadow_nodes() even they use much memory and
system memory is tense.

This patch updates shadow_nodes of anonymous page when swap
cache is add or delete.

Fixes: aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU")
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
---
change for v2
- Include a description of the user-visible effect. Add fixes tag. Modify comments.
Also call workingset_update_node() in clear_shadow_from_swap_cache(). Thanks
to Matthew Wilcox.
---
include/linux/xarray.h | 3 ++-
 mm/swap_state.c        | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 44dd6d6e01bc..5cc1f718fec9 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -1643,7 +1643,8 @@ static inline void xas_set_order(struct xa_state *xas, unsigned long index,
  * @update: Function to call when updating a node.
  *
  * The XArray can notify a caller after it has updated an xa_node.
- * This is advanced functionality and is only needed by the page cache.
+ * This is advanced functionality and is only needed by the page cache
+ * and swap cache.
  */
 static inline void xas_set_update(struct xa_state *xas, xa_update_node_t update)
 {
diff --git a/mm/swap_state.c b/mm/swap_state.c
index cb9aaa00951d..7a003d8abb37 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -94,6 +94,8 @@ int add_to_swap_cache(struct folio *folio, swp_entry_t entry,
 	unsigned long i, nr = folio_nr_pages(folio);
 	void *old;

+	xas_set_update(&xas, workingset_update_node);
+
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 	VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
 	VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
@@ -145,6 +147,8 @@ void __delete_from_swap_cache(struct folio *folio,
 	pgoff_t idx = swp_offset(entry);
 	XA_STATE(xas, &address_space->i_pages, idx);

+	xas_set_update(&xas, workingset_update_node);
+
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 	VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
 	VM_BUG_ON_FOLIO(folio_test_writeback(folio), folio);
@@ -252,6 +256,8 @@ void clear_shadow_from_swap_cache(int type, unsigned long begin,
 		struct address_space *address_space = swap_address_space(entry);
 		XA_STATE(xas, &address_space->i_pages, curr);

+		xas_set_update(&xas, workingset_update_node);
+
 		xa_lock_irq(&address_space->i_pages);
 		xas_for_each(&xas, old, end) {
 			if (!xa_is_value(old))
-- 
2.15.2