Re: [PATCH-v2 12/17] target/file: Add DIF protection init/format support

[Sagi Grimberg <sagig@dev.mellanox.co.il>]

On 1/22/2014 12:28 AM, Nicholas A. Bellinger wrote:
> On Sun, 2014-01-19 at 14:31 +0200, Sagi Grimberg wrote:
>> On 1/19/2014 4:44 AM, Nicholas A. Bellinger wrote:
>>> From: Nicholas Bellinger <nab@linux-iscsi.org>
>>>
>>> This patch adds support for DIF protection init/format support into
>>> the FILEIO backend.
>>>
>>> It involves using a seperate $FILE.protection for storing PI that is
>>> opened via fd_init_prot() using the common pi_prot_type attribute.
>>> The actual formatting of the protection is done via fd_format_prot()
>>> using the common pi_prot_format attribute, that will populate the
>>> initial PI data based upon the currently configured pi_prot_type.
>>>
>>> Based on original FILEIO code from Sagi.
>> Nice! see comments below...
>>
>>> v1 changes:
>>>     - Fix sparse warnings in fd_init_format_buf (Fengguang)
>>>
>>> Cc: Martin K. Petersen <martin.petersen@oracle.com>
>>> Cc: Christoph Hellwig <hch@lst.de>
>>> Cc: Hannes Reinecke <hare@suse.de>
>>> Cc: Sagi Grimberg <sagig@mellanox.com>
>>> Cc: Or Gerlitz <ogerlitz@mellanox.com>
>>> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
>>> ---
>>>    drivers/target/target_core_file.c |  137 +++++++++++++++++++++++++++++++++++++
>>>    drivers/target/target_core_file.h |    4 ++
>>>    2 files changed, 141 insertions(+)
>>>
>>> diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
>>> index 0e34cda..119d519 100644
>>> --- a/drivers/target/target_core_file.c
>>> +++ b/drivers/target/target_core_file.c
>>> @@ -700,6 +700,140 @@ static sector_t fd_get_blocks(struct se_device *dev)
>>>    		       dev->dev_attrib.block_size);
>>>    }
>>>    
>>> +static int fd_init_prot(struct se_device *dev)
>>> +{
>>> +	struct fd_dev *fd_dev = FD_DEV(dev);
>>> +	struct file *prot_file, *file = fd_dev->fd_file;
>>> +	struct inode *inode;
>>> +	int ret, flags = O_RDWR | O_CREAT | O_LARGEFILE | O_DSYNC;
>>> +	char buf[FD_MAX_DEV_PROT_NAME];
>>> +
>>> +	if (!file) {
>>> +		pr_err("Unable to locate fd_dev->fd_file\n");
>>> +		return -ENODEV;
>>> +	}
>>> +
>>> +	inode = file->f_mapping->host;
>>> +	if (S_ISBLK(inode->i_mode)) {
>>> +		pr_err("FILEIO Protection emulation only supported on"
>>> +		       " !S_ISBLK\n");
>>> +		return -ENOSYS;
>>> +	}
>>> +
>>> +	if (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE)
>>> +		flags &= ~O_DSYNC;
>>> +
>>> +	snprintf(buf, FD_MAX_DEV_PROT_NAME, "%s.protection",
>>> +		 fd_dev->fd_dev_name);
>>> +
>>> +	prot_file = filp_open(buf, flags, 0600);
>>> +	if (IS_ERR(prot_file)) {
>>> +		pr_err("filp_open(%s) failed\n", buf);
>>> +		ret = PTR_ERR(prot_file);
>>> +		return ret;
>>> +	}
>>> +	fd_dev->fd_prot_file = prot_file;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static void fd_init_format_buf(struct se_device *dev, unsigned char *buf,
>>> +			       u32 unit_size, u32 *ref_tag, u16 app_tag,
>>> +			       bool inc_reftag)
>>> +{
>>> +	unsigned char *p = buf;
>>> +	int i;
>>> +
>>> +	for (i = 0; i < unit_size; i += dev->prot_length) {
>>> +		*((u16 *)&p[0]) = 0xffff;
>>> +		*((__be16 *)&p[2]) = cpu_to_be16(app_tag);
>>> +		*((__be32 *)&p[4]) = cpu_to_be32(*ref_tag);
>>> +
>>> +		if (inc_reftag)
>>> +			(*ref_tag)++;
>>> +
>>> +		p += dev->prot_length;
>>> +	}
>>> +}
>>> +
>>> +static int fd_format_prot(struct se_device *dev)
>>> +{
>>> +	struct fd_dev *fd_dev = FD_DEV(dev);
>>> +	struct file *prot_fd = fd_dev->fd_prot_file;
>>> +	sector_t prot_length, prot;
>>> +	unsigned char *buf;
>>> +	loff_t pos = 0;
>>> +	u32 ref_tag = 0;
>>> +	int unit_size = FDBD_FORMAT_UNIT_SIZE * dev->dev_attrib.block_size;
>>> +	int rc, ret = 0, size, len;
>>> +	bool inc_reftag = false;
>>> +
>>> +	if (!dev->dev_attrib.pi_prot_type) {
>>> +		pr_err("Unable to format_prot while pi_prot_type == 0\n");
>>> +		return -ENODEV;
>>> +	}
>>> +	if (!prot_fd) {
>>> +		pr_err("Unable to locate fd_dev->fd_prot_file\n");
>>> +		return -ENODEV;
>>> +	}
>>> +
>>> +	switch (dev->dev_attrib.pi_prot_type) {
>> redundant - see below.
>>> +	case TARGET_DIF_TYPE3_PROT:
>>> +		ref_tag = 0xffffffff;
>>> +		break;
>>> +	case TARGET_DIF_TYPE2_PROT:
>>> +	case TARGET_DIF_TYPE1_PROT:
>>> +		inc_reftag = true;
>>> +		break;
>>> +	default:
>>> +		break;
>>> +	}
>>> +
>>> +	buf = vzalloc(unit_size);
>>> +	if (!buf) {
>>> +		pr_err("Unable to allocate FILEIO prot buf\n");
>>> +		return -ENOMEM;
>>> +	}
>>> +
>>> +	prot_length = (dev->transport->get_blocks(dev) + 1) * dev->prot_length;
>>> +	size = prot_length;
>>> +
>>> +	pr_debug("Using FILEIO prot_length: %llu\n",
>>> +		 (unsigned long long)prot_length);
>>> +
>>> +	for (prot = 0; prot < prot_length; prot += unit_size) {
>>> +
>>> +		fd_init_format_buf(dev, buf, unit_size, &ref_tag, 0xffff,
>>> +				   inc_reftag);
>> I didn't send you my latest patches (my fault...).T10-PI format should
>> only place
>> escape values throughout the protection file (fill it with 0xff). so I
>> guess in this case
>> fd_init_formast_buf() boils down to memset(buf, 0xff, unit_size) once
>> before the loop
>> and just loop until prot_length writing buf, no need to address
>> apptag/reftag...
> Yeah, was thinking about just formatting with escape values as mentioned
> above, but thought it might be useful to keep around for pre-populating
> values apptag + reftag values for testing purposes.
>
> --nab
>

OK, but maybe it is better to do that under some debug configuration 
rather then always do that.

Sagi.