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

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

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