On Thursday 09 January 2020 17:53:24 Jan Kara wrote:
> On Thu 09-01-20 14:08:37, Pali Rohár wrote:
> > On Thursday 09 January 2020 13:56:57 Pali Rohár wrote:
> > > On Thursday 09 January 2020 13:44:05 Jan Kara wrote:
> > > > On Wed 08-01-20 23:32:40, Pali Rohár wrote:
> > > > > 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@xxxxxxxxx>
> > > > > > Signed-off-by: Jan Kara <jack@xxxxxxx>
> > > > > > ---
> > > > > > 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".
> > > >
> > > > Fair enough. Let's just always return 0 for disks with VAT partition.
> > > >
> > > > > > + }
> > > > > >
> > > > > > - 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".
> > > >
> > > > Well this is handled by the 'accum == 0xffffffff' condition below. So we
> > > > effectively ignore these values.
> > >
> > > Ok.
> >
> > Now I'm thinking about another scenario: UDF allows you to have two
> > partitions of Type1 (physical) on one volume: one with read-only access
> > type and one with overwritable access type.
> >
> > UDF 2.60 2.2.6.2 says: For a partition with Access Type read-only, the
> > Free Space Table value shall be set to zero. And therefore we should
> > ignore it.
>
> That's what's going to happen (the code ends up ignoring values -1 and 0).
Ok, this could be enough.
> > But current implementation for discs without Metadata partition (all
> > with UDF 2.01) reads free space table (only) from partition
> >
> > unsigned int part = sbi->s_partition;
> >
> > So is this s_partition one with read-only or overwritable access type?
>
> Well, this is the partition we've got fileset from. I presume that's going
> to be on overwritable partition but who knows. Honestly, I have my doubts
> we'll handle disks with two Type1 partitions correctly since I never met
> such disks :) Do you have some disk image to try? :)
Seems that I do not have such disk image.
But if kernel does not support handling such disks then it does not make
sense to do anything with this function which reports free blocks.
> > And to make it more complicated, UDF 2.60 2.2.10 requires that such discs
> > (with two partitions) needs to have also Metadata Partition Map.
>
> But in this case Metadata Partition Map is presumably over the overwritable
> partition so we should fine, shouldn't we?
In both cases I'm just speculating what may happen... Nothing against
this patch.
--
Pali Rohár
pali.rohar@xxxxxxxxx
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