linux-kernel - [PATCH 3.12 68/86] gfs2: avoid uninitialized variable warning

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Message-Id: <c257827e6eea3a421415a1c6771b76f3bcb86df1.1493888632.git.jslaby@suse.cz>
Date:   Thu,  4 May 2017 11:04:33 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Bob Peterson <rpeterso@...hat.com>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 68/86] gfs2: avoid uninitialized variable warning

From: Arnd Bergmann <arnd@...db.de>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 67893f12e5374bbcaaffbc6e570acbc2714ea884 upstream.

We get a bogus warning about a potential uninitialized variable
use in gfs2, because the compiler does not figure out that we
never use the leaf number if get_leaf_nr() returns an error:

fs/gfs2/dir.c: In function 'get_first_leaf':
fs/gfs2/dir.c:802:9: warning: 'leaf_no' may be used uninitialized in this function [-Wmaybe-uninitialized]
fs/gfs2/dir.c: In function 'dir_split_leaf':
fs/gfs2/dir.c:1021:8: warning: 'leaf_no' may be used uninitialized in this function [-Wmaybe-uninitialized]

Changing the 'if (!error)' to 'if (!IS_ERR_VALUE(error))' is
sufficient to let gcc understand that this is exactly the same
condition as in IS_ERR() so it can optimize the code path enough
to understand it.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Bob Peterson <rpeterso@...hat.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 fs/gfs2/dir.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index 2e5fc268d324..bdef6fef651c 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -763,7 +763,7 @@ static int get_first_leaf(struct gfs2_inode *dip, u32 index,
 	int error;
 
 	error = get_leaf_nr(dip, index, &leaf_no);
-	if (!error)
+	if (!IS_ERR_VALUE(error))
 		error = get_leaf(dip, leaf_no, bh_out);
 
 	return error;
@@ -974,7 +974,7 @@ static int dir_split_leaf(struct inode *inode, const struct qstr *name)
 
 	index = name->hash >> (32 - dip->i_depth);
 	error = get_leaf_nr(dip, index, &leaf_no);
-	if (error)
+	if (IS_ERR_VALUE(error))
 		return error;
 
 	/*  Get the old leaf block  */
-- 
2.12.2