On Wed, Apr 19, 2017 at 7:04 PM, Martin K. Petersen
<martin.petersen@xxxxxxxxxx> wrote:
> Ilya Dryomov <idryomov@xxxxxxxxx> writes:
>
> Ilya,
>
>> Commit 25520d55cdb6 ("block: Inline blk_integrity in struct gendisk")
>> introduced blk_integrity_revalidate(), which seems to assume ownership
>> of the stable pages flag and unilaterally clears it if no blk_integrity
>> profile is registered:
>>
>> if (bi->profile)
>> disk->queue->backing_dev_info->capabilities |=
>> BDI_CAP_STABLE_WRITES;
>> else
>> disk->queue->backing_dev_info->capabilities &=
>> ~BDI_CAP_STABLE_WRITES;
>>
>> It's called from revalidate_disk() and rescan_partitions(), making it
>> impossible to enable stable pages for drivers that support partitions
>> and don't use blk_integrity: while the call in revalidate_disk() can be
>> trivially worked around (see zram, which doesn't support partitions and
>> hence gets away with zram_revalidate_disk()), rescan_partitions() can
>> be triggered from userspace at any time. This breaks rbd, where the
>> ceph messenger is responsible for generating/verifying CRCs.
>>
>> Since blk_integrity_{un,}register() "must" be used for (un)registering
>> the integrity profile with the block layer, move BDI_CAP_STABLE_WRITES
>> setting there. This way drivers that call blk_integrity_register() and
>> use integrity infrastructure won't interfere with drivers that don't
>> but still want stable pages.
>
> I seem to recall that the reason for the revalidate hook was that either
> NVMe or nvdimm had to register an integrity profile prior to the actual
> format being known.
>
> So while I am OK with the change from a SCSI perspective, I think we
> need Keith and Dan to ack it.
Looks good to me,
Tested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
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