Re: UDF filesystem image with Write-Once UDF Access Type

[Jan Kara]

On Thu 01-08-19 09:35:30, Jan Kara wrote:
> > If you want to play with Write-Once Access Type, use recent version of
> > mkudffs and choose --media-type=cdr option, which generates UDF
> > filesystem suitable for CD-R (Write-Once Access Type with VAT and other
> > UDF options according to UDF specification).
> 
> Reasonably recent kernels should have this bug fixed and mount such fs read
> only. That being said I've tested current upstream kernel with a media
> created with --media-type=cdr and mounting failed with:
> 
> UDF-fs: error (device ubdb): udf_read_inode: (ino 524287) failed !bh
> UDF-fs: error (device ubdb): udf_read_inode: (ino 524286) failed !bh
> UDF-fs: error (device ubdb): udf_read_inode: (ino 524285) failed !bh
> UDF-fs: error (device ubdb): udf_read_inode: (ino 524284) failed !bh
> UDF-fs: Scanning with blocksize 2048 failed
> 
> So there's something fishy either in the created image or the kernel...
> Didn't debug this further yet.

Hum, looks like a problem with mkudffs. Relevant debug messages look like:

UDF-fs: fs/udf/super.c:671:udf_check_vsd: Starting at sector 16 (2048 byte sectors)
UDF-fs: fs/udf/super.c:824:udf_load_pvoldesc: recording time 2019/08/01 09:47 (1078)
UDF-fs: fs/udf/super.c:836:udf_load_pvoldesc: volIdent[] = 'LinuxUDF'
UDF-fs: fs/udf/super.c:844:udf_load_pvoldesc: volSetIdent[] = '1564645645200563LinuxUDF'
UDF-fs: fs/udf/super.c:1462:udf_load_logicalvol: Partition (0:0) type 1 on volume 1
UDF-fs: fs/udf/super.c:1462:udf_load_logicalvol: Partition (1:0) type 2 on volume 1
UDF-fs: fs/udf/super.c:1471:udf_load_logicalvol: FileSet found in LogicalVolDesc at block=0, partition=1
UDF-fs: fs/udf/super.c:1218:udf_load_partdesc: Searching map: (0 == 0)
UDF-fs: fs/udf/super.c:1060:udf_fill_partdesc_info: Partition (0 type 1511) starts at physical 288, block length 524000
UDF-fs: fs/udf/super.c:1060:udf_fill_partdesc_info: Partition (1 type 2012) starts at physical 288, block length 524000
UDF-fs: fs/udf/misc.c:223:udf_read_tagged: location mismatch block 524287, tag 0 != 523999
UDF-fs: error (device ubdb): udf_read_inode: (ino 524287) failed !bh

So the fact that location tag was 0 in block 524287 (which should contain
VAT inode) suggests there's something fishy with how / where mkudffs
creates the VAT inode. Can you have a look?

BTW, mkudffs messages look like:
filename=/tmp/image
label=LinuxUDF
uuid=1564645645200563
blocksize=2048
blocks=524288
udfrev=2.01
vatblock=319
start=0, blocks=16, type=RESERVED 
start=16, blocks=4, type=VRS 
start=20, blocks=76, type=USPACE 
start=96, blocks=16, type=MVDS 
start=112, blocks=16, type=USPACE 
start=128, blocks=1, type=LVID 
start=129, blocks=95, type=USPACE 
start=224, blocks=16, type=RVDS 
start=240, blocks=16, type=USPACE 
start=256, blocks=1, type=ANCHOR 
start=257, blocks=31, type=USPACE 
start=288, blocks=524000, type=PSPACE 

which suggests that VAT was indeed allocated somewhere in the beginning of
the partition.

								Honza
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR