Re: [PATCH 3/4] nilfs2: add nilfs_sufile_set_suinfo to update segment usage

[Andrew Morton <akpm@linux-foundation.org>]

On Tue,  4 Feb 2014 01:50:43 +0900 Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> wrote:

> From: Andreas Rohner <andreas.rohner@gmx.net>
> 
> This patch introduces the nilfs_sufile_set_suinfo function, which
> expects an array of nilfs_suinfo_update structures and updates the
> segment usage information accordingly.
> 
> This is basically a helper function for the newly introduced
> NILFS_IOCTL_SET_SUINFO ioctl.
> 
> ..
>
> --- a/fs/nilfs2/sufile.c
> +++ b/fs/nilfs2/sufile.c
> @@ -870,6 +870,137 @@ ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
>  }
>  
>  /**
> + * nilfs_sufile_set_suinfo - sets segment usage info
> + * @sufile: inode of segment usage file
> + * @buf: array of suinfo_update
> + * @supsz: byte size of suinfo_update
> + * @nsup: size of suinfo_update array
> + *
> + * Description: Takes an array of nilfs_suinfo_update structs and updates
> + * segment usage accordingly. Only the fields indicated by the sup_flags
> + * are updated.
> + *
> + * Return Value: On success, 0 is returned. On error, one of the
> + * following negative error codes is returned.
> + *
> + * %-EIO - I/O error.
> + *
> + * %-ENOMEM - Insufficient amount of memory available.
> + *
> + * %-EINVAL - Invalid values in input (segment number, flags or nblocks)
> + */
> +ssize_t nilfs_sufile_set_suinfo(struct inode *sufile, void *buf,
> +				unsigned supsz, size_t nsup)
> +{
> +	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
> +	struct buffer_head *header_bh, *bh;
> +	struct nilfs_suinfo_update *sup, *supend = buf + supsz * nsup;
> +	struct nilfs_segment_usage *su;
> +	void *kaddr;
> +	unsigned long blkoff, prev_blkoff;
> +	int cleansi, cleansu, dirtysi, dirtysu;
> +	long ncleaned = 0, ndirtied = 0;
> +	int ret = 0;
> +
> +	if (unlikely(nsup == 0))
> +		return ret;
> +
> +	for (sup = buf; sup < supend; sup = (void *)sup + supsz) {
> +		if (sup->sup_segnum >= nilfs->ns_nsegments
> +			|| (sup->sup_flags &
> +				(~0UL << __NR_NILFS_SUINFO_UPDATE_FIELDS))
> +			|| (nilfs_suinfo_update_nblocks(sup) &&
> +				sup->sup_sui.sui_nblocks >
> +				nilfs->ns_blocks_per_segment))
> +			return -EINVAL;
> +	}
> +
> +	down_write(&NILFS_MDT(sufile)->mi_sem);
> +
> +	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
> +	if (ret < 0)
> +		goto out_sem;
> +
> +	sup = buf;
> +	blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
> +	ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
> +	if (ret < 0)
> +		goto out_header;
> +
> +	for (;;) {
> +		kaddr = kmap_atomic(bh->b_page);

Can this buffer_head really be in highmem?

> +		su = nilfs_sufile_block_get_segment_usage(
> +			sufile, sup->sup_segnum, bh, kaddr);

Returns an address wthin the kmapped page.  I really hope
nilfs_sufile_block_get_segment_usage() cannot return an address outside
that page - it appears to do quite a lot of unchecked arithmetic which
is dependent on stuff which was read from the disk.  What it that was
interfered with or otherwise corrupted?

> +		if (nilfs_suinfo_update_lastmod(sup))
> +			su->su_lastmod = cpu_to_le64(sup->sup_sui.sui_lastmod);
> +
> +		if (nilfs_suinfo_update_nblocks(sup))
> +			su->su_nblocks = cpu_to_le32(sup->sup_sui.sui_nblocks);
> +
> +		if (nilfs_suinfo_update_flags(sup)) {
> +			/*
> +			 * Active flag is a virtual flag projected by running
> +			 * nilfs kernel code - drop it not to write it to
> +			 * disk.
> +			 */
> +			sup->sup_sui.sui_flags &=
> +					~(1UL << NILFS_SEGMENT_USAGE_ACTIVE);
> +
> +			cleansi = nilfs_suinfo_clean(&sup->sup_sui);
> +			cleansu = nilfs_segment_usage_clean(su);
> +			dirtysi = nilfs_suinfo_dirty(&sup->sup_sui);
> +			dirtysu = nilfs_segment_usage_dirty(su);
> +
> +			if (cleansi && !cleansu)
> +				++ncleaned;
> +			else if (!cleansi && cleansu)
> +				--ncleaned;
> +
> +			if (dirtysi && !dirtysu)
> +				++ndirtied;
> +			else if (!dirtysi && dirtysu)
> +				--ndirtied;
> +
> +			su->su_flags = cpu_to_le32(sup->sup_sui.sui_flags);
> +		}
> +
> +		kunmap_atomic(kaddr);

flush_dcache_page()?  Can the page be mapped by userspace?

> +		sup = (void *)sup + supsz;
> +		if (sup >= supend)
> +			break;
> +
> +		prev_blkoff = blkoff;
> +		blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
> +		if (blkoff == prev_blkoff)
> +			continue;
> +
> +		/* get different block */
> +		mark_buffer_dirty(bh);
> +		brelse(bh);

put_bh() will suffice - we know bh != NULL.

> +		ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
> +		if (unlikely(ret < 0))
> +			goto out_mark;
> +	}
> +	mark_buffer_dirty(bh);
> +	brelse(bh);

ditto

> + out_mark:
> +	if (ncleaned || ndirtied) {
> +		nilfs_sufile_mod_counter(header_bh, (u64)ncleaned,
> +				(u64)ndirtied);
> +		NILFS_SUI(sufile)->ncleansegs += ncleaned;
> +	}
> +	nilfs_mdt_mark_dirty(sufile);
> + out_header:
> +	brelse(header_bh);
> + out_sem:
> +	up_write(&NILFS_MDT(sufile)->mi_sem);
> +	return ret;
> +}
> +
> +/**