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Subject: Re: [PATCH] xfs: Fix xfs_dir2_sf_entry_t size check
To:     Vincenzo Frascino <vincenzo.frascino@arm.com>,
        darrick.wong@oracle.com, linux-xfs@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20200109141459.21808-1-vincenzo.frascino@arm.com>
From:   Eric Sandeen <sandeen@sandeen.net>
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Date:   Thu, 9 Jan 2020 09:01:38 -0600
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On 1/9/20 8:14 AM, Vincenzo Frascino wrote:
> xfs_check_ondisk_structs() verifies that the sizes of the data types
> used by xfs are correct via the XFS_CHECK_STRUCT_SIZE() macro.
> 
> xfs_dir2_sf_entry_t size is set erroneously to 3 which breaks the
> compilation with the assertion below:
> 
> In file included from linux/include/linux/string.h:6,
>                  from linux/include/linux/uuid.h:12,
>                  from linux/fs/xfs/xfs_linux.h:10,
>                  from linux/fs/xfs/xfs.h:22,
>                  from linux/fs/xfs/xfs_super.c:7:
> In function ‘xfs_check_ondisk_structs’,
>     inlined from ‘init_xfs_fs’ at linux/fs/xfs/xfs_super.c:2025:2:
> linux/include/linux/compiler.h:350:38:
>     error: call to ‘__compiletime_assert_107’ declared with attribute
>     error: XFS: sizeof(xfs_dir2_sf_entry_t) is wrong, expected 3
>     _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
> 
> Restore the correct behavior defining the correct size.

# pahole -C xfs_dir2_sf_entry fs/xfs/xfs.o 

struct xfs_dir2_sf_entry {
	__u8                       namelen;              /*     0     1 */
	__u8                       offset[2];            /*     1     2 */
	__u8                       name[0];              /*     3     0 */

	/* size: 3, cachelines: 1, members: 3 */
	/* last cacheline: 3 bytes */
};

Can you please the same command on your machine, along with which arm abi is
in use etc just for clarity?

-Eric

> Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
>  fs/xfs/xfs_ondisk.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_ondisk.h b/fs/xfs/xfs_ondisk.h
> index b6701b4f59a9..ee487ddc60c7 100644
> --- a/fs/xfs/xfs_ondisk.h
> +++ b/fs/xfs/xfs_ondisk.h
> @@ -104,7 +104,7 @@ xfs_check_ondisk_structs(void)
>  	XFS_CHECK_STRUCT_SIZE(xfs_dir2_leaf_hdr_t,		16);
>  	XFS_CHECK_STRUCT_SIZE(xfs_dir2_leaf_t,			16);
>  	XFS_CHECK_STRUCT_SIZE(xfs_dir2_leaf_tail_t,		4);
> -	XFS_CHECK_STRUCT_SIZE(xfs_dir2_sf_entry_t,		3);
> +	XFS_CHECK_STRUCT_SIZE(xfs_dir2_sf_entry_t,		4);
>  	XFS_CHECK_OFFSET(xfs_dir2_sf_entry_t, namelen,		0);
>  	XFS_CHECK_OFFSET(xfs_dir2_sf_entry_t, offset,		1);
>  	XFS_CHECK_OFFSET(xfs_dir2_sf_entry_t, name,		3);
>