> static ssize_t jfs_quota_read(struct super_block *sb, int type, char *data,
> + size_t len, loff_t pos)
> {
> struct inode *inode = sb_dqopt(sb)->files[type];
> + struct address_space *mapping = inode->i_mapping;
> size_t toread;
> + pgoff_t index;
> loff_t i_size = i_size_read(inode);
>
> + if (pos > i_size)
> return 0;
> + if (pos + len > i_size)
> + len = i_size - pos;
> toread = len;
> + index = pos / PAGE_SIZE;
> +
> while (toread > 0) {
> + struct folio *folio = read_mapping_folio(mapping, index, NULL);
> + size_t tocopy = PAGE_SIZE - offset_in_page(pos);
> + void *src;
> +
> + if (IS_ERR(folio))
> + return PTR_ERR(folio);
> +
> + src = kmap_local_folio(folio, offset_in_folio(folio, pos));
> + memcpy(data, src, tocopy);
> + kunmap_local(src);
It would be great to have a memcpy_from_folio like the existing
memcpy_from_page for this.
> + folio_put(folio);
>
> toread -= tocopy;
> data += tocopy;
> + pos += tocopy;
> + index++;
> }
> return len;
And this whole helper is generic now. It might be worth to move it
into fs/quota/dquot.c as generic_quota_read.
