linux-kernel - Re: [PATCH] xfs: Fix xfs_dir2_sf_entry

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Date:   Thu, 9 Jan 2020 15:35:46 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Eric Sandeen <sandeen@...deen.net>, darrick.wong@...cle.com,
        linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: Fix xfs_dir2_sf_entry_t size check

Hi Eric,

On 09/01/2020 15:01, Eric Sandeen wrote:
> 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?
>

The abi is arm32 eabihf. You can reproduce my scenario using randconfig with
seed 0x72F68201.

In this case I get size 4, hence my patch.

If I enable xfs on the defconfig though size is 3 accordingly to what you have
reported. I will continue the investigation.

Vincenzo

> -Eric
> 
>> Cc: "Darrick J. Wong" <darrick.wong@...cle.com>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....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);
>>

-- 
Regards,
Vincenzo

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