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 - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html