From: "Pali Rohár" <firstname.lastname@example.org> To: Jan Kara <email@example.com>, "Steven J. Magnani" <firstname.lastname@example.org>, Roald Strauss <email@example.com>, firstname.lastname@example.org, email@example.com Subject: UDF filesystem image with Write-Once UDF Access Type Date: Fri, 12 Jul 2019 12:02:24 +0200 [thread overview] Message-ID: <20190712100224.s2chparxszlbnill@pali> (raw) Hello, I had discussion with Roald and based on his tests, Linux kernel udf.ko driver mounts UDF filesystem image with Write-Once UDF Access Type as normal read/write filesystem. I think this is a bug as Write-Once Access Type is defined that existing blocks on filesystem cannot be rewritten. Only new blocks can be appended after end of device. Basically it means special HW support from underlying media, e.g. for optical medias packet-writing technique (or ability to burn new session) and CDROM_LAST_WRITTEN ioctl to locate "current" end of device. In my opinion without support for additional layer, kernel should treat UDF Write-Once Access Type as read-only mount for userspace. And not classic read/write mount. 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). Also in git master of udftools has mkduffs now new option --read-only which creates UDF image with Read-Only Access Type. It seems that udf.ko does not support updating VAT table, so probably it should treat also filesystem with VAT as read-only too. -- Pali Rohár firstname.lastname@example.org
next reply other threads:[~2019-07-12 10:02 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-07-12 10:02 Pali Rohár [this message] 2019-07-26 17:44 ` Steve Magnani 2019-08-01 7:44 ` Jan Kara 2019-08-01 7:35 ` Jan Kara 2019-08-01 8:38 ` Jan Kara 2019-08-01 8:57 ` Pali Rohár 2019-08-02 10:28 ` Jan Kara 2019-08-01 8:44 ` Pali Rohár 2019-08-01 10:21 ` Roald Strauss
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