From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Walle <michael@walle.cc>
Date: Tue, 16 Aug 2016 13:41:21 +0200
Subject: [U-Boot] [RFC PATCH 3/4] ext4: fix endianess problems in ext4
 write support
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 <2198104.q3j2TPqOcn@pebbles.site>
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Hi Stefan,

Am 2016-08-14 03:50, schrieb Stefan Bruens:
> On Freitag, 12. August 2016 15:16:20 CEST Michael Walle wrote:
>> All fields were accessed directly instead of using the proper byte 
>> swap
>> functions. Thus, ext4 write support was only usable on little-endian
>> architectures. Fix this.
>> 
>> Signed-off-by: Michael Walle <michael@walle.cc>
> 
> I have tested this on sandbox (x86_64), no regressions found. Some 
> remarks
> below.
> 
> Reviewed-by: Stefan Br?ns <stefan.bruens@rwth-aachen.de>
> Tested-by: Stefan Br?ns <stefan.bruens@rwth-aachen.de>
> 

[snip]

>> @@ -2234,7 +2246,7 @@ int ext4fs_mount(unsigned part_length)
>>  	 * and we do not support metadata_csum (and cannot reliably find
>>  	 * files when it is set.  Refuse to mount.
>>  	 */
>> -	if (data->sblock.feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT) {
>> +	if (le32_to_cpu(data->sblock.feature_incompat) &
>> EXT4_FEATURE_INCOMPAT_64BIT) { printf("Unsupported feature found 
>> (64bit,
>> possibly metadata_csum), not mounting\n"); goto fail;
>>  	}
> 
> This should have a if ((data->sblock.revision_level !=0) && ... in 
> front,
> features are not defined for revision 0. Applies to other places as 
> well ...
> 

are you sure about that? I can't find any code in the kernel where 
features are only valid if revision > 0. Also, I couldn't find anything 
in the ext4 documentation wiki:

https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout

-michael