On 2011-12-06, at 10:01 PM, Andreas Dilger wrote:
> On 2011-11-28, at 4:26 PM, Darrick J. Wong wrote:
>> Record the type of checksum algorithm we're using for metadata in the
>> superblock, in case we ever want/need to change the algorithm.
>>
>> @@ -982,6 +982,9 @@ extern void ext4_set_bits(void *bm, int cur, int len);
>> +/* Metadata checksum algorithm codes */
>> +#define EXT4_CRC32C_CHKSUM 1
>
> It might make sense to add a constant for the existing CRC16 type:
>
> #define EXT4_CRC16_CHKSUM 0
> #define EXT4_CRC32C_CHKSUM 1
> #define EXT4_CHKSUM_MAX 1
Never mind, I had EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM on the brain.
CRC16 is completely unrelated to EXT4_FEATURE_RO_COMPAT_METADATA_CSUM.
>> +static int ext4_verify_csum_type(struct super_block *sb,
>> + struct ext4_super_block *es)
>> +{
>> + if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
>> + EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
>> + return 1;
>> +
>> + return es->s_checksum_type == EXT4_CRC32C_CHKSUM;
>> +}
>
> Then this checks "return es->s_checksum_type <= EXT4_CHKSUM_MAX;".
>
>> @@ -3182,6 +3192,14 @@ static int ext4_fill_super(struct super_block *sb,
>> + /* Check for a known checksum algorithm */
>> + if (!ext4_verify_csum_type(sb, es)) {
>> + ext4_msg(sb, KERN_ERR, "VFS: Found ext4 filesystem with "
>> + "unknown checksum algorithm.");
>
> It would be useful if this error message printed the checksum type.
This is still a valid comment.
Cheers, Andreas
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