Re: [dm-devel] [PATCH 26/27] scsi: sd: Separate zeroout and discard command choices

[Martin K. Petersen]

Paolo,

> Should this be conditional on lbprz, lbpws, lbpws10 and max_ws_blocks?

It is intentional that things can be overridden from userland for
devices that report the "wrong" thing. We do the same for discard so
people can set up udev rules.

-- 
Martin K. Petersen  Oracle Linux Engineering

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

Re: [dm-devel] [PATCH 26/27] scsi: sd: Separate zeroout and discard command choices

[Paolo Bonzini]

On 05/04/2017 19:21, Christoph Hellwig wrote:
> +static ssize_t
> +zeroing_mode_store(struct device *dev, struct device_attribute *attr,
> +const char *buf, size_t count)
> +{
> + struct scsi_disk *sdkp = to_scsi_disk(dev);
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EACCES;
> +
> +
> + if (!strncmp(buf, zeroing_mode[SD_ZERO_WRITE], 20))
> + sdkp->zeroing_mode = SD_ZERO_WRITE;
> + else if (!strncmp(buf, zeroing_mode[SD_ZERO_WS], 20))
> + sdkp->zeroing_mode = SD_ZERO_WS;
> + else if (!strncmp(buf, zeroing_mode[SD_ZERO_WS16_UNMAP], 20))
> + sdkp->zeroing_mode = SD_ZERO_WS16_UNMAP;
> + else if (!strncmp(buf, zeroing_mode[SD_ZERO_WS10_UNMAP], 20))
> + sdkp->zeroing_mode = SD_ZERO_WS10_UNMAP;

Should this be conditional on lbprz, lbpws, lbpws10 and max_ws_blocks?

Thanks,

Paolo

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

Re: [dm-devel] [PATCH 26/27] scsi: sd: Separate zeroout and discard command choices

[Hannes Reinecke]

On 04/05/2017 07:21 PM, Christoph Hellwig wrote:
> From: "Martin K. Petersen" 
> 
> Now that zeroout and discards are distinct operations we need to
> separate the policy of choosing the appropriate command. Create a
> zeroing_mode which can be one of:
> 
> write:Zeroout assist not present, use regular WRITE
> writesame:Allow WRITE SAME(10/16) with a zeroed payload
> writesame_16_unmap:   Allow WRITE SAME(16) with UNMAP
> writesame_10_unmap:   Allow WRITE SAME(10) with UNMAP
> 
> The last two are conditional on the device being thin provisioned with
> LBPRZ=1 and LBPWS=1 or LBPWS10=1 respectively.
> 
> Whether to set the UNMAP bit or not depends on the REQ_NOUNMAP flag. And
> if none of the _unmap variants are supported, regular WRITE SAME will be
> used if the device supports it.
> 
> The zeroout_mode is exported in sysfs and the detected mode for a given
> device can be overridden using the string constants above.
> 
> With this change in place we can now issue WRITE SAME(16) with UNMAP set
> for block zeroing applications that require hard guarantees and
> logical_block_size granularity. And at the same time use the UNMAP
> command with the device's preferred granulary and alignment for discard
> operations.
> 
> Signed-off-by: Martin K. Petersen 
> Signed-off-by: Christoph Hellwig 
> ---
>  drivers/scsi/sd.c | 56 
> ---
>  drivers/scsi/sd.h |  8 
>  2 files changed, 61 insertions(+), 3 deletions(-)
> 
Reviewed-by: Hannes Reinecke 

Cheers,

Hannes
-- 
Dr. Hannes ReineckeTeamlead Storage & Networking
h...@suse.de   +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel