Re: [PATCH v4 8/9] scsi: sd_zbc: always revalidate zones for disks supporting head depopulation

[Damien Le Moal <dlemoal@kernel.org>]

On 2026/10/09 11:32, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] scsi: sd: data race on struct scsi_disk bitfields can clobber WCE or modify_zones_supported
> --
> 
> commit a445da75935ac3ec4cee9fc525679769cf828446
> Author: Damien Le Moal <dlemoal@kernel.org>
> 
> scsi: sd_zbc: always revalidate zones for disks supporting head depopulation
> 
> This commit introduces a new check for ZBC devices that support data preserving
> head depopulation to ensure zone conditions are properly revalidated. It adds
> a new modify_zones_supported bitfield to struct scsi_disk and sets it during
> sd_zbc_read_zones(). The flag is then used to skip or perform zone revalidation
> depending on the disk's support for this feature.
> 
>> diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
>> index 574af82430169..6a72371fee786 100644
>> --- a/drivers/scsi/sd.h
>> +++ b/drivers/scsi/sd.h
>> @@ -156,6 +156,7 @@ struct scsi_disk {
>>  	unsigned	ignore_medium_access_errors : 1;
>>  	unsigned	rscs : 1; /* reduced stream control support */
>>  	unsigned	use_atomic_write_boundary : 1;
>> +	unsigned	modify_zones_supported : 1;
>>  };
>>  #define to_scsi_disk(obj) container_of(obj, struct scsi_disk, disk_dev)
> 
> [ ... ]
> 
>> diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
>> index 8cbf171e6fabf..1bf5f7ea0d9c5 100644
>> --- a/drivers/scsi/sd_zbc.c
>> +++ b/drivers/scsi/sd_zbc.c
> [ ... ]
>> @@ -620,6 +641,9 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, struct queue_limits *lim,
>>  	if (ret != 0)
>>  		goto err;
>>  
>> +	/* Check if REMOVE ELEMENT AND MODIFY ZONES is supported. */
>> +	sdkp->modify_zones_supported = sd_zbc_check_modify_zones(sdkp, buf);
>         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> [Severity: High]
> Does this bitfield assignment introduce a data race that can silently corrupt
> neighboring bitfields like WCE?

Maybe... But this is not a new issue. All "flags" of a SCSI disks are defined as
"unsigned int :1" bits. Everything should be rewritten to use a proper unsigne
long bitfield with bit manipulation functions. So I am not going to fix that here.


-- 
Damien Le Moal
Western Digital Research