Andreas Dilger wrote:
> On Jan 02, 2008 14:01 -0600, Eric Sandeen wrote:
>> This patch:
>>
>> changes fe_len to an int, I don't think we need it to be a long,
>> looking at how it's used (should it be a grpblk_t?) Also change
>> anything assigned to return value of mb_find_extent, since it returns
>> fe_len.
>>
>> changes anything that does groupno * EXT4_BLOCKS_PER_GROUP
>> or pa->pa_pstart + <whatever> to an ext4_fsblk_t
>>
>> fixes up any related formats
>>
>> The change to ext4_mb_scan_aligned to avoid a 64-bit modulo
>> could use an extra look I think.
>>
>> @@ -1732,17 +1735,18 @@ static void ext4_mb_scan_aligned(struct
>> BUG_ON(sbi->s_stripe == 0);
>>
>> - /* find first stripe-aligned block */
>> - i = e4b->bd_group * EXT4_BLOCKS_PER_GROUP(sb)
>> - + le32_to_cpu(sbi->s_es->s_first_data_block);
>> - i = ((i + sbi->s_stripe - 1) / sbi->s_stripe) * sbi->s_stripe;
>> - i = (i - le32_to_cpu(sbi->s_es->s_first_data_block))
>> - % EXT4_BLOCKS_PER_GROUP(sb);
>
>> + /* find first stripe-aligned block in group */
>> + a = e4b->bd_group * EXT4_BLOCKS_PER_GROUP(sb)
>> + + le32_to_cpu(sbi->s_es->s_first_data_block);
>> + a = (a + sbi->s_stripe - 1) & ~((ext4_fsblk_t)sbi->s_stripe - 1);
>> + a = a - le32_to_cpu(sbi->s_es->s_first_data_block);
>> + i = do_div(a, EXT4_BLOCKS_PER_GROUP(sb));
>
> I don't think this is correct... This code should only be used if s_stripe
> is NOT a power-of-two value, otherwise we can just use the buddy maps to
> find aligned chunks. As a result I don't think that "& (s_stripe - 1)"
> change is equivalent to "/ s_stripe * s_stripe".
Hmmm ok let me re-check that then.
(...curses 64-bit math trickiness...)
>> while (i < sb->s_blocksize * 8) {
>> if (!mb_test_bit(i, bitmap)) {
>
> Hrmmm, I thought this should be "while (i < EXT4_BLOCKS_PER_GROUP(sb))"
> and not "sb->s_blocksize * 8"? Did that fix get lost somewhere?
I did wonder about that.... wondered about the magic 8 number but forgot
to comment.
Thanks,
-Eric
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