Re: [PATCH] udf: Fix free space reporting for metadata and virtual partitions

["Pali Rohár" <pali.rohar@gmail.com>]

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On Wednesday 08 January 2020 13:19:19 Jan Kara wrote:
> Free space on filesystems with metadata or virtual partition maps
> currently gets misreported. This is because these partitions are just
> remapped onto underlying real partitions from which keep track of free
> blocks. Take this remapping into account when counting free blocks as
> well.
> 
> Reported-by: Pali Rohár <pali.rohar@gmail.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/udf/super.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> I plan to take this patch to my tree.
> 
> diff --git a/fs/udf/super.c b/fs/udf/super.c
> index 8c28e93e9b73..b89e420a4b85 100644
> --- a/fs/udf/super.c
> +++ b/fs/udf/super.c
> @@ -2492,17 +2492,26 @@ static unsigned int udf_count_free_table(struct super_block *sb,
>  static unsigned int udf_count_free(struct super_block *sb)
>  {
>  	unsigned int accum = 0;
> -	struct udf_sb_info *sbi;
> +	struct udf_sb_info *sbi = UDF_SB(sb);
>  	struct udf_part_map *map;
> +	unsigned int part = sbi->s_partition;
> +	int ptype = sbi->s_partmaps[part].s_partition_type;
> +
> +	if (ptype == UDF_METADATA_MAP25) {
> +		part = sbi->s_partmaps[part].s_type_specific.s_metadata.
> +							s_phys_partition_ref;
> +	} else if (ptype == UDF_VIRTUAL_MAP15 || ptype == UDF_VIRTUAL_MAP20) {
> +		part = UDF_I(sbi->s_vat_inode)->i_location.
> +							partitionReferenceNum;

Hello! I do not think that it make sense to report "free blocks" for
discs with Virtual partition. By definition of VAT, all blocks prior to
VAT are already "read-only" and therefore these blocks cannot be use for
writing new data by any implementation. And because VAT is stored on the
last block, in our model all blocks are "occupied".

> +	}
>  
> -	sbi = UDF_SB(sb);
>  	if (sbi->s_lvid_bh) {
>  		struct logicalVolIntegrityDesc *lvid =
>  			(struct logicalVolIntegrityDesc *)
>  			sbi->s_lvid_bh->b_data;
> -		if (le32_to_cpu(lvid->numOfPartitions) > sbi->s_partition) {
> +		if (le32_to_cpu(lvid->numOfPartitions) > part) {
>  			accum = le32_to_cpu(
> -					lvid->freeSpaceTable[sbi->s_partition]);
> +					lvid->freeSpaceTable[part]);

And in any case freeSpaceTable should not be used for discs with VAT.
And we should ignore its value for discs with VAT.

UDF 2.60 2.2.6.2: Free Space Table values be maintained ... except ...
for a virtual partition ...

And same applies for "partition with Access Type pseudo-overwritable".

>  			if (accum == 0xFFFFFFFF)
>  				accum = 0;
>  		}
> @@ -2511,7 +2520,7 @@ static unsigned int udf_count_free(struct super_block *sb)
>  	if (accum)
>  		return accum;
>  
> -	map = &sbi->s_partmaps[sbi->s_partition];
> +	map = &sbi->s_partmaps[part];
>  	if (map->s_partition_flags & UDF_PART_FLAG_UNALLOC_BITMAP) {
>  		accum += udf_count_free_bitmap(sb,
>  					       map->s_uspace.s_bitmap);

-- 
Pali Rohár
pali.rohar@gmail.com

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