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".
> 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?
There are a few other changes in the patch related to this fix:
https://bugzilla.lustre.org/attachment.cgi?id=13275
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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