linux-kernel - [PATCH] FS-Cache: print hexadecimal value for special cookies type

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Message-Id: <20170419203819.21951-1-jeremy.lefaure@lse.epita.fr>
Date:   Wed, 19 Apr 2017 16:38:19 -0400
From:   Jérémy Lefaure 
        <jeremy.lefaure@....epita.fr>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-cachefs@...hat.com, linux-kernel@...r.kernel.org,
        Jérémy Lefaure 
        <jeremy.lefaure@....epita.fr>
Subject: [PATCH] FS-Cache: print hexadecimal value for special cookies type

When building object-list.o, gcc 6 raises a warning on the sprintf call
in fscache_objlist_show:

  CC      fs/fscache/object-list.o
fs/fscache/object-list.c: In function ‘fscache_objlist_show’:
fs/fscache/object-list.c:265:19: warning: ‘sprintf’ may write a
terminating nul past the end of the destination [-Wformat-overflow=]
    sprintf(_type, "%02u", cookie->def->type);
                   ^~~~~~
fs/fscache/object-list.c:265:4: note: ‘sprintf’ output between 3 and 4
bytes into a destination of size 3
    sprintf(_type, "%02u", cookie->def->type);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Moreover, the documentation says that we should have an hex value for
special cookies (see Documentation/filesystems/caching/fscache.txt).

Printing hexadecimal value for special cookies fixes the overflow
warning and complies with the documentation.

Signed-off-by: Jérémy Lefaure <jeremy.lefaure@....epita.fr>
---
 fs/fscache/object-list.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
index 67f940892ef8..d51303124889 100644
--- a/fs/fscache/object-list.c
+++ b/fs/fscache/object-list.c
@@ -262,7 +262,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 			type = "DT";
 			break;
 		default:
-			sprintf(_type, "%02u", cookie->def->type);
+			sprintf(_type, "%02x", cookie->def->type);
 			type = _type;
 			break;
 		}
-- 
2.12.2