Re: [PATCH, RFC] Don't do page stablization if !CONFIG_BLKDEV_INTEGRITY

[Boaz Harrosh <bharrosh@panasas.com>]

On 03/07/2012 07:45 PM, Martin K. Petersen wrote:
>>>>>> "Boaz" == Boaz Harrosh <bharrosh@panasas.com> writes:
> 
> Boaz> As I stated many times before, the device should have a property
> Boaz> that says if it needs stable pages or not. The candidates for
> Boaz> stable pages are:
> 
> Boaz> 	- DIF/DIX enabled devices
> Boaz> 	- RAID-1/4/5/6 devices
> Boaz> 	- iscsi devices with data digest signature
> Boaz> 	- Any other checksum enabled block device.
> 
> Boaz> A fedora distro will have CONFIG_BLKDEV_INTEGRITY set then you are
> Boaz> always out of luck, even with devices that can care less.
> 
> Boaz> Please submit a proper patch, even a temporary mount option. But
> Boaz> this is ABI. The best is to find where to export it as part of the
> Boaz> device's properties sysfs dir.
> 
> We could do something like this:
> 

Yes, this one is perfect.

Combined with Darrick's patch to actually inspect the flag at the filesystem level
is the solution I want.

When submitted I will also send a patch to set .needs_stable_pages in iscsi
when needed.

Thanks, Martin
Boaz

> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 5680b91..442a0df 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -125,6 +125,7 @@ void blk_set_default_limits(struct queue_limits *lim)
>  	lim->io_opt = 0;
>  	lim->misaligned = 0;
>  	lim->cluster = 1;
> +	lim->needs_stable_pages = false;
>  }
>  EXPORT_SYMBOL(blk_set_default_limits);
>  
> @@ -571,6 +572,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
>  	t->cluster &= b->cluster;
>  	t->discard_zeroes_data &= b->discard_zeroes_data;
>  
> +	t->needs_stable_pages &= b->needs_stable_pages;
> +
>  	/* Physical block size a multiple of the logical block size? */
>  	if (t->physical_block_size & (t->logical_block_size - 1)) {
>  		t->physical_block_size = t->logical_block_size;
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 5b85d91..d464aca 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -161,6 +161,11 @@ static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *pag
>  	return queue_var_show(queue_discard_zeroes_data(q), page);
>  }
>  
> +static ssize_t queue_needs_stable_pages_show(struct request_queue *q, char *page)
> +{
> +	return queue_var_show(q->limits.needs_stable_pages, page);
> +}
> +
>  static ssize_t queue_write_same_max_show(struct request_queue *q, char *page)
>  {
>  	return sprintf(page, "%llu\n",
> @@ -364,6 +369,11 @@ static struct queue_sysfs_entry queue_discard_zeroes_data_entry = {
>  	.show = queue_discard_zeroes_data_show,
>  };
>  
> +static struct queue_sysfs_entry queue_needs_stable_pages_entry = {
> +	.attr = {.name = "needs_stable_pages", .mode = S_IRUGO },
> +	.show = queue_needs_stable_pages_show,
> +};
> +
>  static struct queue_sysfs_entry queue_write_same_max_entry = {
>  	.attr = {.name = "write_same_max_bytes", .mode = S_IRUGO },
>  	.show = queue_write_same_max_show,
> @@ -416,6 +426,7 @@ static struct attribute *default_attrs[] = {
>  	&queue_discard_granularity_entry.attr,
>  	&queue_discard_max_entry.attr,
>  	&queue_discard_zeroes_data_entry.attr,
> +	&queue_needs_stable_pages_entry.attr,
>  	&queue_write_same_max_entry.attr,
>  	&queue_nonrot_entry.attr,
>  	&queue_nomerges_entry.attr,
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 26eff46..146bed4 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -1752,10 +1752,11 @@ static void sd_read_protection_type(struct scsi_disk *sdkp, unsigned char *buffe
>  		return;
>  	}
>  
> -	if (scsi_host_dif_capable(sdp->host, type))
> +	if (scsi_host_dif_capable(sdp->host, type)) {
>  		sd_printk(KERN_NOTICE, sdkp,
>  			  "Enabling DIF Type %u protection\n", type);
> -	else
> +		sdkp->disk->queue->limits.needs_stable_pages = true;
> +	} else
>  		sd_printk(KERN_NOTICE, sdkp,
>  			  "Disabling DIF Type %u protection\n", type);
>  }
> diff --git a/drivers/scsi/sd_dif.c b/drivers/scsi/sd_dif.c
> index 0cb39ff..9dc330c 100644
> --- a/drivers/scsi/sd_dif.c
> +++ b/drivers/scsi/sd_dif.c
> @@ -338,6 +338,8 @@ void sd_dif_config_host(struct scsi_disk *sdkp)
>  	sd_printk(KERN_NOTICE, sdkp,
>  		  "Enabling DIX %s protection\n", disk->integrity->name);
>  
> +	disk->queue->limits.needs_stable_pages = true;
> +
>  	/* Signal to block layer that we support sector tagging */
>  	if (dif && type && sdkp->ATO) {
>  		if (type == SD_DIF_TYPE3_PROTECTION)
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 92956b7..a5a33db 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -266,6 +266,8 @@ struct queue_limits {
>  	unsigned char		discard_misaligned;
>  	unsigned char		cluster;
>  	unsigned char		discard_zeroes_data;
> +
> +	bool			needs_stable_pages;
>  };
>  
>  struct request_queue {