Userspace regression with 6baca7601bde ("scsi: target: drop unused pi_prot_format attribute storage")

[Laura Abbott]

Hi,

Fedora got a bug report of a new permission denied error with 5.0-rc2:

>   File "/usr/lib/python3.7/site-packages/rtslib_fb/utils.py", line 100, in fread
>     with open(path, 'r') as file_fd:
> PermissionError: [Errno 13] Permission denied: '/sys/kernel/config/target/core/fileio_28/xxx/attrib/pi_prot_format'

This looks like an intentional behavior change with

commit 6baca7601bdee2e57f20c45d63eb53b89b33e816
Author: David Disseldorp <ddiss@xxxxxxx>
Date:   Fri Nov 23 18:36:11 2018 +0100

    scsi: target: drop unused pi_prot_format attribute storage
    
    On write, the pi_prot_format configfs attribute invokes the device
    format_prot() callback if present. Read dumps the contents of
    se_dev_attrib.pi_prot_format which is always zero.  Make the configfs
    attribute write-only, and drop the always zero se_dev_attrib.pi_prot_format
    storage.
    
    Signed-off-by: David Disseldorp <ddiss@xxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>


Unfortunately, existing code that's opening with read permissions is now broken.
Can this be reverted? Full bug at https://bugzilla.redhat.com/show_bug.cgi?id=1667505

Thanks,
Laura