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A previous change was introduced to prevent data loss during a power-on reset when a tape is present inside the drive. This commit set the "pos_unknown" flag to true to avoid operations that could compromise data by performing actions from an untracked position. The relevant change is commit9604eea5bd("scsi: st: Add third party poweron reset handling") As a consequence of this change, a new issue has surfaced: the driver now returns an "Input/output error" even for empty drives when the drive, host, or bus is reset. This issue stems from the "flush_buffer" function, which first checks whether the "pos_unknown" flag is set. If the flag is set, the user will encounter an "Input/output error" until the tape position is known again. This behavior differs from the previous implementation, where empty drives were not affected at system start up time, allowing tape software to send commands to the driver to retrieve the drive's status and other information. The current behavior prioritizes the "pos_unknown" flag over the "ST_NO_TAPE" status, leading to issues for software that detects drives during system startup. This software will receive an "Input/output error" until a tape is loaded and its position is known. To resolve this, the "ST_NO_TAPE" status should take priority when the drive is empty, allowing communication with the drive following a power-on reset. At the same time, the change should continue to protect data by maintaining the "pos_unknown" flag when the drive contains a tape and its position is unknown. Signed-off-by: Rafael Rocha <rrochavi@fnal.gov> Link: https://lore.kernel.org/r/20240905173921.10944-1-rrochavi@fnal.gov Fixes:9604eea5bd("scsi: st: Add third party poweron reset handling") Acked-by: Kai Mäkisara <kai.makisara@kolumbus.fi> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.