[PATCH] bug:roundup_pow_of_two(size) will return 0 when size > 2^63 because of overflow problem. fix:when size > max, return max. (when newsize > max will return max originally)

[? ?? <weilongpingshu@hotmail.com>]

Signed-off-by: LongPing.WEI <weilongpingshu@hotmail.com>
---
 mm/readahead.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/readahead.c b/mm/readahead.c
index c4ca702..4941f04 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -248,7 +248,12 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
  */
 static unsigned long get_init_ra_size(unsigned long size, unsigned long max)
 {
-	unsigned long newsize = roundup_pow_of_two(size);
+	unsigned long newsize;
+
+	if (size > max)
+		return max;
+
+	newsize = roundup_pow_of_two(size);
 
 	if (newsize <= max / 32)
 		newsize = newsize * 4;
-- 
2.7.4

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