Re: [PATCH v6] fat: Batched discard support for fat

OGAWA Hirofumi
2011-03-29T05:04:12Z

Kyungmin Park <kmpark@infradead.org> writes:

> +int fat_trim_fs(struct super_block *sb, struct fstrim_range *range)
> +{
> + struct msdos_sb_info *sbi = MSDOS_SB(sb);
> + struct fatent_operations *ops = sbi->fatent_ops;
> + struct fat_entry fatent;
> + unsigned long reada_blocks, reada_mask, cur_block;
> + int err, free, count, entry;
> + int start, len, minlen, trimmed;
> +
> + start = range->start >> sb->s_blocksize_bits;
> + len = range->len >> sb->s_blocksize_bits;
> + len = round_down(start + len, sbi->sec_per_clus);
> + start = round_up(start, sbi->sec_per_clus);
> + minlen = range->minlen >> sb->s_blocksize_bits;
> + minlen = round_up(minlen, sbi->sec_per_clus);
> + trimmed = 0;
> + count = 0;
> + err = -EINVAL;

Sorry for didn't mention at previous. You can use ->cluster_size, and
->cluster_bits.

> + if (start >= sbi->max_cluster)
> + goto out;
> +
> + len = (len > sbi->max_cluster) ? sbi->max_cluster : len;

[...]

> + trimmed += free;
> + }
> + range->len = (u64)(trimmed * sbi->sec_per_clus) << sb->s_blocksize_bits;
> + fatent_brelse(&fatent);
> +out:
> + unlock_fat(sbi);
> + return err;

Again, this ioctl's design is unclear, and seems to be strange. I
wouldn't want to add this before clearing it. Please explain what is
right behavior.

E.g. if user specified 0-1024 and FS data block was actually started at
2048. What is right behavior? And if the end of blocks, what returned?
For now, it seems to return range->len == 0 on both cases.

Well, so, my suggestion is providing this like flat one extent
file. I.e. FS have to map actual block placement to flat. And result
also like write/read (return bytes as trimed, and at EOF returns 0).

Thanks.
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>