scsi: Adding lock to protect variables of bit-field in struct scsi_device

scsi: Adding lock to protect variables of bit-field in struct scsi_device

[jiangyiwen]

Hi guys,

I'm sorry if someone else has already asked the same question before,
but here's what we are facing with scsi mid-level.

Variables of bit-field in struct scsi_device are not protected by
lock, such as no_report_opcodes, is_visible and so on. I guess
everyone think these variable can't be accessed by multi-processes,
but unfortunately, I came across one problem as follows:

Assuming there is a process A which is executing the operation of
adding device, so it will call scsi_sysfs_add_sdev, and eventually
it will start an async kworker B to execute sd_probe_async.
In this way, process A will set "sdev->is_visible = 1" in the function
of scsi_sysfs_add_sdev, in the meantime, aysnc kworker B may set
"sdev->no_report_opcodes = 1" in the function of sd_read_write_same.
Neither of the variables are protected by any lock, setting the value
of no_report_opcodes may change value of is_visible from 1 to 0, which
alters the bit field unexpectedly. Did I miss anything?

So I'd like to know whether these variable of bit-field should
be protected by lock or not.

Please advise. Thanks in advance!

Best regards,
Yiwen