2020-04-22 11:02:19

by Greg Kroah-Hartman

Subject: [PATCH 4.4 091/100] ext2: fix empty body warnings when -Wextra is used

From: Randy Dunlap <[email protected]>

[ Upstream commit 44a52022e7f15cbaab957df1c14f7a4f527ef7cf ]

When EXT2_ATTR_DEBUG is not defined, modify the 2 debug macros
to use the no_printk() macro instead of <nothing>.
This fixes gcc warnings when -Wextra is used:

../fs/ext2/xattr.c:252:42: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
../fs/ext2/xattr.c:258:42: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
../fs/ext2/xattr.c:330:42: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
../fs/ext2/xattr.c:872:45: warning: suggest braces around empty body in an ‘else’ statement [-Wempty-body]

I have verified that the only object code change (with gcc 7.5.0) is
the reversal of some instructions from 'cmp a,b' to 'cmp b,a'.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Randy Dunlap <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: [email protected]
Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
fs/ext2/xattr.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index 22d817dc821e9..6f6f4f89a2f0c 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -55,6 +55,7 @@

#include <linux/buffer_head.h>
#include <linux/init.h>
+#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/mbcache.h>
#include <linux/quotaops.h>
@@ -85,8 +86,8 @@
printk("\n"); \
} while (0)
#else
-# define ea_idebug(f...)
-# define ea_bdebug(f...)
+# define ea_idebug(inode, f...) no_printk(f)
+# define ea_bdebug(bh, f...) no_printk(f)
#endif

static int ext2_xattr_set2(struct inode *, struct buffer_head *,
--
2.20.1

2020-04-25 11:50:54

by Joe Perches

Subject: Re: [PATCH 4.4 091/100] ext2: fix empty body warnings when -Wextra is used

On Sat, 2020-04-25 at 04:43 -0700, Joe Perches wrote:
> On Wed, 2020-04-22 at 11:57 +0200, Greg Kroah-Hartman wrote:
> > From: Randy Dunlap <[email protected]>
> >
> > [ Upstream commit 44a52022e7f15cbaab957df1c14f7a4f527ef7cf ]
> >
> > When EXT2_ATTR_DEBUG is not defined, modify the 2 debug macros
> > to use the no_printk() macro instead of <nothing>.
> > This fixes gcc warnings when -Wextra is used:
> >
> > ../fs/ext2/xattr.c:252:42: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
> > ../fs/ext2/xattr.c:258:42: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
> > ../fs/ext2/xattr.c:330:42: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
> > ../fs/ext2/xattr.c:872:45: warning: suggest braces around empty body in an ‘else’ statement [-Wempty-body]
> >
> > I have verified that the only object code change (with gcc 7.5.0) is
> > the reversal of some instructions from 'cmp a,b' to 'cmp b,a'.
>
> It'd be better to use the ext4 style defines:
>
> fs/ext4/xattr.c:# define ea_idebug(inode, fmt, ...) \
> fs/ext4/xattr.c- printk(KERN_DEBUG "inode %s:%lu: " fmt "\n", \
> fs/ext4/xattr.c- inode->i_sb->s_id, inode->i_ino, ##__VA_ARGS__)
> fs/ext4/xattr.c:# define ea_bdebug(bh, fmt, ...) \
> fs/ext4/xattr.c- printk(KERN_DEBUG "block %pg:%lu: " fmt "\n", \
> fs/ext4/xattr.c- bh->b_bdev, (unsigned long)bh->b_blocknr, ##__VA_ARGS__)
> --
> fs/ext4/xattr.c:# define ea_idebug(inode, fmt, ...) no_printk(fmt, ##__VA_ARGS__)
> fs/ext4/xattr.c:# define ea_bdebug(bh, fmt, ...) no_printk(fmt, ##__VA_ARGS__)
>
> So the output logging won't be split across multiple lines.

And beyond that, why is a -Wextra warning being fixed in -stable at all?