On Tuesday 07 January 2020 15:45:18 Jan Kara wrote: > Hello! > > On Thu 26-12-19 12:37:50, Pali Rohár wrote: > > During testing of udfinfo tool (from udftools project) I found that > > udfinfo's implementation for calculating free space does not work when > > UDF filesystem has Metadata partition (according to OSTA UDF 2.50). > > > > Year ago in udfinfo for calculating free space I used same algorithm as > > is implemented in kernel UDF driver, function udf_count_free(). So I > > suspect kernel driver could have it incorrectly implemented too, but I'm > > not sure. So I'm sending this email to let you know about it. > > > > What is the problem? UDF Metadata partition is stored directly on UDF > > Physical partition and therefore free space calculation needs to be done > > from Physical one (same applies for Virtual partition). But Metadata > > partition contains mapping table for logical <--> physical blocks, so > > reading data needs to be done always from Metadata partition. Also in > > UDF terminology are two different things: Partition and Partition Map. > > And "partition number" is a bit misleading as sometimes it refers to > > "Partition" and sometimes to "Partition Map" what are two different > > things. > > Thanks for the note! You're right that we probably misreport amount of free > space in the UDF filesystems with Metadata partition. Luckily the kernel > driver supports filesystems with Metadata partition or Virtual partition > only in read-only mode so the bug does not cause any real harm. For discs with Virtual partition I used in udfinfo different algorithm for calculating free space: Free are only those blocks which are after VAT block (therefore unrecorded blocks). > > Calculation problem in udfinfo I fixed in this commit: > > https://github.com/pali/udftools/commit/1763c9f899bdbdb68b1a44a8cb5edd5141107043 > > Thanks for the link, I'll fixup the kernel code. BTW, how did you test > this? Do you have any UDF image with Metadata partition? I have CD, DVD, HD-DVD and BD images with just one file (so they have lot of empty space) in all variants (plain, Sparing, VAT) and all possible UDF revisions (1.02 - 2.60) created by some very very ancient Windows Nero software. Some of them discovered bugs in libblkid UDF implementation and are therefore included as part of util-linux project for running util-linux tests. Plain and Sparing UDF 2.50 and 2.60 images have Metadata partition as required by specification. If you want I can send you a whole pack of all those images. -- Pali Rohár pali.rohar@xxxxxxxxx
