linux-kernel - [PATCH next] mm/shmem: fix shmem folio swapoff hang

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Message-ID: <c32bee8a-f0aa-245-f94e-24dd271924fa@google.com>
Date:   Sat, 21 May 2022 19:53:04 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Matthew Wilcox <willy@...radead.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH next] mm/shmem: fix shmem folio swapoff hang

Shmem swapoff makes no progress: the index to indices is not incremented.
But "ret" is no longer a return value, so use folio_batch_count() instead.

Fixes: da08e9b79323 ("mm/shmem: convert shmem_swapin_page() to shmem_swapin_folio()")
Signed-off-by: Hugh Dickins <hughd@...gle.com>
---

 mm/shmem.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1171,7 +1171,6 @@ static int shmem_find_swap_entries(struc
 	XA_STATE(xas, &mapping->i_pages, start);
 	struct folio *folio;
 	swp_entry_t entry;
-	unsigned int ret = 0;
 
 	rcu_read_lock();
 	xas_for_each(&xas, folio, ULONG_MAX) {
@@ -1189,7 +1188,7 @@ static int shmem_find_swap_entries(struc
 		if (swp_type(entry) != type)
 			continue;
 
-		indices[ret] = xas.xa_index;
+		indices[folio_batch_count(fbatch)] = xas.xa_index;
 		if (!folio_batch_add(fbatch, folio))
 			break;