From: "Pali Rohár" <pali.rohar@gmail.com>
To: linux-fsdevel@vger.kernel.org, Jan Kara <jack@suse.com>
Subject: udf_count_free() and UDF discs with Metadata partition
Date: Thu, 26 Dec 2019 12:37:50 +0100 [thread overview]
Message-ID: <20191226113750.rcfmbs643sfnpixq@pali> (raw)
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Hello!
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.
Calculation problem in udfinfo I fixed in this commit:
https://github.com/pali/udftools/commit/1763c9f899bdbdb68b1a44a8cb5edd5141107043
--
Pali Rohár
pali.rohar@gmail.com
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next reply other threads:[~2019-12-26 11:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-26 11:37 Pali Rohár [this message]
2020-01-07 14:45 ` udf_count_free() and UDF discs with Metadata partition Jan Kara
2020-01-07 15:01 ` Pali Rohár
2020-01-07 15:29 ` Jan Kara
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