[PATCH] readahead: fix return value of page_cache_next_miss() when no hole is found

[Chi Zhiling <chizhiling@163.com>]

From: Chi Zhiling <chizhiling@kylinos.cn>

max_scan in page_cache_next_miss always decreases to zero when no hole
is found, causing the return value to be index + 0.

Fix this by preserving the max_scan value throughout the loop.

Fixes: 901a269ff3d5 ("filemap: fix page_cache_next_miss() when no hole found")
Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
---
 mm/filemap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index b5e784f34d98..148be65be1cd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1767,8 +1767,9 @@ pgoff_t page_cache_next_miss(struct address_space *mapping,
 			     pgoff_t index, unsigned long max_scan)
 {
 	XA_STATE(xas, &mapping->i_pages, index);
+	unsigned long nr = max_scan;
 
-	while (max_scan--) {
+	while (nr--) {
 		void *entry = xas_next(&xas);
 		if (!entry || xa_is_value(entry))
 			return xas.xa_index;
-- 
2.43.0