[PATCH] xfs: avoid -Wint-in-bool-context warning in xfs_bmap_util.c

[PATCH] xfs: avoid -Wint-in-bool-context warning in xfs_bmap_util.c

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

XFS triggers gcc 7's -Wint-in-bool-context warning (on by default with
-Wall), which warns about arithmetic in a boolean context that has no
effect on the result:

    In file included from fs/xfs/xfs_inode.h:22:0,
                     from fs/xfs/xfs_bmap_util.c:29:
    fs/xfs/xfs_bmap_util.c: In function ‘xfs_swap_extents_check_format’:
    fs/xfs/libxfs/xfs_inode_fork.h:90:30: warning: ‘<<’ in boolean context, did you mean ‘<’ ? [-Wint-in-bool-context]
     #define XFS_IFORK_BOFF(ip)  ((int)((ip)->i_d.di_forkoff << 3))
                                 ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    fs/xfs/xfs_bmap_util.c:1620:7: note: in expansion of macro ‘XFS_IFORK_BOFF’
       if (XFS_IFORK_BOFF(ip) &&
           ^~~~~~~~~~~~~~
    fs/xfs/libxfs/xfs_inode_fork.h:90:30: warning: ‘<<’ in boolean context, did you mean ‘<’ ? [-Wint-in-bool-context]
     #define XFS_IFORK_BOFF(ip)  ((int)((ip)->i_d.di_forkoff << 3))
                                 ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    fs/xfs/xfs_bmap_util.c:1630:7: note: in expansion of macro ‘XFS_IFORK_BOFF’
       if (XFS_IFORK_BOFF(tip) &&
           ^~~~~~~~~~~~~~

This is more or less a false positive, because the useless arithmetic is
just the left shift in XFS_IFORK_BOFF().  Use XFS_IFORK_Q() instead to
make the warnings go away, while having the same behavior and being more
consistent with other places in XFS which also use XFS_IFORK_Q().

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/xfs/xfs_bmap_util.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 7ac80a1facf2..05a6fdf5976d 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -1613,7 +1613,7 @@ xfs_swap_extents_check_format(
 	 * extent format...
 	 */
 	if (tip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
-		if (XFS_IFORK_BOFF(ip) &&
+		if (XFS_IFORK_Q(ip) &&
 		    XFS_BMAP_BMDR_SPACE(tip->i_df.if_broot) > XFS_IFORK_BOFF(ip))
 			return -EINVAL;
 		if (XFS_IFORK_NEXTENTS(tip, XFS_DATA_FORK) <=
@@ -1623,7 +1623,7 @@ xfs_swap_extents_check_format(
 
 	/* Reciprocal target->temp btree format checks */
 	if (ip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
-		if (XFS_IFORK_BOFF(tip) &&
+		if (XFS_IFORK_Q(tip) &&
 		    XFS_BMAP_BMDR_SPACE(ip->i_df.if_broot) > XFS_IFORK_BOFF(tip))
 			return -EINVAL;
 		if (XFS_IFORK_NEXTENTS(ip, XFS_DATA_FORK) <=
-- 
2.13.0

Re: [PATCH] xfs: avoid -Wint-in-bool-context warning in xfs_bmap_util.c

[Darrick J. Wong]

On Fri, Jun 02, 2017 at 09:21:07PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> XFS triggers gcc 7's -Wint-in-bool-context warning (on by default with
> -Wall), which warns about arithmetic in a boolean context that has no
> effect on the result:
> 
>     In file included from fs/xfs/xfs_inode.h:22:0,
>                      from fs/xfs/xfs_bmap_util.c:29:
>     fs/xfs/xfs_bmap_util.c: In function ‘xfs_swap_extents_check_format’:
>     fs/xfs/libxfs/xfs_inode_fork.h:90:30: warning: ‘<<’ in boolean context, did you mean ‘<’ ? [-Wint-in-bool-context]
>      #define XFS_IFORK_BOFF(ip)  ((int)((ip)->i_d.di_forkoff << 3))
>                                  ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     fs/xfs/xfs_bmap_util.c:1620:7: note: in expansion of macro ‘XFS_IFORK_BOFF’
>        if (XFS_IFORK_BOFF(ip) &&
>            ^~~~~~~~~~~~~~
>     fs/xfs/libxfs/xfs_inode_fork.h:90:30: warning: ‘<<’ in boolean context, did you mean ‘<’ ? [-Wint-in-bool-context]
>      #define XFS_IFORK_BOFF(ip)  ((int)((ip)->i_d.di_forkoff << 3))
>                                  ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>     fs/xfs/xfs_bmap_util.c:1630:7: note: in expansion of macro ‘XFS_IFORK_BOFF’
>        if (XFS_IFORK_BOFF(tip) &&
>            ^~~~~~~~~~~~~~
> 
> This is more or less a false positive, because the useless arithmetic is
> just the left shift in XFS_IFORK_BOFF().  Use XFS_IFORK_Q() instead to
> make the warnings go away, while having the same behavior and being more
> consistent with other places in XFS which also use XFS_IFORK_Q().
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Arnd Bergmann already sent the exact same patch[1] for 4.13, but, er,
thanks for spotting this! :)

--D

[1] https://marc.info/?l=linux-xfs&m=149498134833721&w=2

> ---
>  fs/xfs/xfs_bmap_util.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 7ac80a1facf2..05a6fdf5976d 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -1613,7 +1613,7 @@ xfs_swap_extents_check_format(
>  	 * extent format...
>  	 */
>  	if (tip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
> -		if (XFS_IFORK_BOFF(ip) &&
> +		if (XFS_IFORK_Q(ip) &&
>  		    XFS_BMAP_BMDR_SPACE(tip->i_df.if_broot) > XFS_IFORK_BOFF(ip))
>  			return -EINVAL;
>  		if (XFS_IFORK_NEXTENTS(tip, XFS_DATA_FORK) <=
> @@ -1623,7 +1623,7 @@ xfs_swap_extents_check_format(
>  
>  	/* Reciprocal target->temp btree format checks */
>  	if (ip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
> -		if (XFS_IFORK_BOFF(tip) &&
> +		if (XFS_IFORK_Q(tip) &&
>  		    XFS_BMAP_BMDR_SPACE(ip->i_df.if_broot) > XFS_IFORK_BOFF(tip))
>  			return -EINVAL;
>  		if (XFS_IFORK_NEXTENTS(ip, XFS_DATA_FORK) <=
> -- 
> 2.13.0
> 
> --
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Re: [PATCH] xfs: avoid -Wint-in-bool-context warning in xfs_bmap_util.c

[Eric Biggers]

On Fri, Jun 02, 2017 at 09:50:41PM -0700, Darrick J. Wong wrote:
> 
> Arnd Bergmann already sent the exact same patch[1] for 4.13, but, er,
> thanks for spotting this! :)
> 
> --D
> 
> [1] https://marc.info/?l=linux-xfs&m=149498134833721&w=2
> 

Oh, okay.  I didn't see anything in
git://git.kernel.org/pub/scm/fs/xfs/xfs-linux.git#for-next; I guess it hasn't
been pushed out yet.

Eric