sg.c

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		error = PTR_ERR(sdp);
		goto out;
	}

	class_set_devdata(cl_dev, sdp);
	error = cdev_add(cdev, MKDEV(SCSI_GENERIC_MAJOR, sdp->index), 1);
	if (error)
		goto cdev_add_err;

	sdp->cdev = cdev;
	if (sg_sysfs_valid) {
		struct class_device * sg_class_member;

		sg_class_member = class_device_create(sg_sysfs_class, NULL,
				MKDEV(SCSI_GENERIC_MAJOR, sdp->index),
				cl_dev->dev, "%s",
				disk->disk_name);
		if (IS_ERR(sg_class_member))
			printk(KERN_WARNING "sg_add: "
				"class_device_create failed\n");
		class_set_devdata(sg_class_member, sdp);
		error = sysfs_create_link(&scsidp->sdev_gendev.kobj, 
					  &sg_class_member->kobj, "generic");
		if (error)
			printk(KERN_ERR "sg_add: unable to make symlink "
					"'generic' back to sg%d\n", sdp->index);
	} else
		printk(KERN_WARNING "sg_add: sg_sys Invalid\n");

	sdev_printk(KERN_NOTICE, scsidp,
		    "Attached scsi generic sg%d type %d\n", sdp->index,
		    scsidp->type);

	return 0;

cdev_add_err:
	write_lock_irqsave(&sg_index_lock, iflags);
	idr_remove(&sg_index_idr, sdp->index);
	write_unlock_irqrestore(&sg_index_lock, iflags);
	kfree(sdp);

out:
	put_disk(disk);
	if (cdev)
		cdev_del(cdev);
	return error;
}

static void
sg_remove(struct class_device *cl_dev, struct class_interface *cl_intf)
{
	struct scsi_device *scsidp = to_scsi_device(cl_dev->dev);
	Sg_device *sdp = class_get_devdata(cl_dev);
	unsigned long iflags;
	Sg_fd *sfp;
	Sg_fd *tsfp;
	Sg_request *srp;
	Sg_request *tsrp;
	int delay;

	if (!sdp)
		return;

	delay = 0;
	write_lock_irqsave(&sg_index_lock, iflags);
	if (sdp->headfp) {
		sdp->detached = 1;
		for (sfp = sdp->headfp; sfp; sfp = tsfp) {
			tsfp = sfp->nextfp;
			for (srp = sfp->headrp; srp; srp = tsrp) {
				tsrp = srp->nextrp;
				if (sfp->closed || (0 == sg_srp_done(srp, sfp)))
					sg_finish_rem_req(srp);
			}
			if (sfp->closed) {
				scsi_device_put(sdp->device);
				__sg_remove_sfp(sdp, sfp);
			} else {
				delay = 1;
				wake_up_interruptible(&sfp->read_wait);
				kill_fasync(&sfp->async_qp, SIGPOLL,
					    POLL_HUP);
			}
		}
		SCSI_LOG_TIMEOUT(3, printk("sg_remove: dev=%d, dirty\n", sdp->index));
		if (NULL == sdp->headfp) {
			idr_remove(&sg_index_idr, sdp->index);
		}
	} else {	/* nothing active, simple case */
		SCSI_LOG_TIMEOUT(3, printk("sg_remove: dev=%d\n", sdp->index));
		idr_remove(&sg_index_idr, sdp->index);
	}
	write_unlock_irqrestore(&sg_index_lock, iflags);

	sysfs_remove_link(&scsidp->sdev_gendev.kobj, "generic");
	class_device_destroy(sg_sysfs_class, MKDEV(SCSI_GENERIC_MAJOR, sdp->index));
	cdev_del(sdp->cdev);
	sdp->cdev = NULL;
	put_disk(sdp->disk);
	sdp->disk = NULL;
	if (NULL == sdp->headfp)
		kfree(sdp);

	if (delay)
		msleep(10);	/* dirty detach so delay device destruction */
}

module_param_named(scatter_elem_sz, scatter_elem_sz, int, S_IRUGO | S_IWUSR);
module_param_named(def_reserved_size, def_reserved_size, int,
		   S_IRUGO | S_IWUSR);
module_param_named(allow_dio, sg_allow_dio, int, S_IRUGO | S_IWUSR);

MODULE_AUTHOR("Douglas Gilbert");
MODULE_DESCRIPTION("SCSI generic (sg) driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(SG_VERSION_STR);
MODULE_ALIAS_CHARDEV_MAJOR(SCSI_GENERIC_MAJOR);

MODULE_PARM_DESC(scatter_elem_sz, "scatter gather element "
                "size (default: max(SG_SCATTER_SZ, PAGE_SIZE))");
MODULE_PARM_DESC(def_reserved_size, "size of buffer reserved for each fd");
MODULE_PARM_DESC(allow_dio, "allow direct I/O (default: 0 (disallow))");

static int __init
init_sg(void)
{
	int rc;

	if (scatter_elem_sz < PAGE_SIZE) {
		scatter_elem_sz = PAGE_SIZE;
		scatter_elem_sz_prev = scatter_elem_sz;
	}
	if (def_reserved_size >= 0)
		sg_big_buff = def_reserved_size;
	else
		def_reserved_size = sg_big_buff;

	rc = register_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0), 
				    SG_MAX_DEVS, "sg");
	if (rc)
		return rc;
        sg_sysfs_class = class_create(THIS_MODULE, "scsi_generic");
        if ( IS_ERR(sg_sysfs_class) ) {
		rc = PTR_ERR(sg_sysfs_class);
		goto err_out;
        }
	sg_sysfs_valid = 1;
	rc = scsi_register_interface(&sg_interface);
	if (0 == rc) {
#ifdef CONFIG_SCSI_PROC_FS
		sg_proc_init();
#endif				/* CONFIG_SCSI_PROC_FS */
		return 0;
	}
	class_destroy(sg_sysfs_class);
err_out:
	unregister_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0), SG_MAX_DEVS);
	return rc;
}

static void __exit
exit_sg(void)
{
#ifdef CONFIG_SCSI_PROC_FS
	sg_proc_cleanup();
#endif				/* CONFIG_SCSI_PROC_FS */
	scsi_unregister_interface(&sg_interface);
	class_destroy(sg_sysfs_class);
	sg_sysfs_valid = 0;
	unregister_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0),
				 SG_MAX_DEVS);
	idr_destroy(&sg_index_idr);
}

static int
sg_start_req(Sg_request * srp)
{
	int res;
	Sg_fd *sfp = srp->parentfp;
	sg_io_hdr_t *hp = &srp->header;
	int dxfer_len = (int) hp->dxfer_len;
	int dxfer_dir = hp->dxfer_direction;
	Sg_scatter_hold *req_schp = &srp->data;
	Sg_scatter_hold *rsv_schp = &sfp->reserve;

	SCSI_LOG_TIMEOUT(4, printk("sg_start_req: dxfer_len=%d\n", dxfer_len));
	if ((dxfer_len <= 0) || (dxfer_dir == SG_DXFER_NONE))
		return 0;
	if (sg_allow_dio && (hp->flags & SG_FLAG_DIRECT_IO) &&
	    (dxfer_dir != SG_DXFER_UNKNOWN) && (0 == hp->iovec_count) &&
	    (!sfp->parentdp->device->host->unchecked_isa_dma)) {
		res = sg_build_direct(srp, sfp, dxfer_len);
		if (res <= 0)	/* -ve -> error, 0 -> done, 1 -> try indirect */
			return res;
	}
	if ((!sg_res_in_use(sfp)) && (dxfer_len <= rsv_schp->bufflen))
		sg_link_reserve(sfp, srp, dxfer_len);
	else {
		res = sg_build_indirect(req_schp, sfp, dxfer_len);
		if (res) {
			sg_remove_scat(req_schp);
			return res;
		}
	}
	return 0;
}

static void
sg_finish_rem_req(Sg_request * srp)
{
	Sg_fd *sfp = srp->parentfp;
	Sg_scatter_hold *req_schp = &srp->data;

	SCSI_LOG_TIMEOUT(4, printk("sg_finish_rem_req: res_used=%d\n", (int) srp->res_used));
	if (srp->res_used)
		sg_unlink_reserve(sfp, srp);
	else
		sg_remove_scat(req_schp);
	sg_remove_request(sfp, srp);
}

static int
sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp, int tablesize)
{
	int sg_bufflen = tablesize * sizeof(struct scatterlist);
	gfp_t gfp_flags = GFP_ATOMIC | __GFP_NOWARN;

	/*
	 * TODO: test without low_dma, we should not need it since
	 * the block layer will bounce the buffer for us
	 *
	 * XXX(hch): we shouldn't need GFP_DMA for the actual S/G list.
	 */
	if (sfp->low_dma)
		 gfp_flags |= GFP_DMA;
	schp->buffer = kzalloc(sg_bufflen, gfp_flags);
	if (!schp->buffer)
		return -ENOMEM;
	sg_init_table(schp->buffer, tablesize);
	schp->sglist_len = sg_bufflen;
	return tablesize;	/* number of scat_gath elements allocated */
}

#ifdef SG_ALLOW_DIO_CODE
/* vvvvvvvv  following code borrowed from st driver's direct IO vvvvvvvvv */
	/* TODO: hopefully we can use the generic block layer code */

/* Pin down user pages and put them into a scatter gather list. Returns <= 0 if
   - mapping of all pages not successful
   (i.e., either completely successful or fails)
*/
static int 
st_map_user_pages(struct scatterlist *sgl, const unsigned int max_pages, 
	          unsigned long uaddr, size_t count, int rw)
{
	unsigned long end = (uaddr + count + PAGE_SIZE - 1) >> PAGE_SHIFT;
	unsigned long start = uaddr >> PAGE_SHIFT;
	const int nr_pages = end - start;
	int res, i, j;
	struct page **pages;

	/* User attempted Overflow! */
	if ((uaddr + count) < uaddr)
		return -EINVAL;

	/* Too big */
        if (nr_pages > max_pages)
		return -ENOMEM;

	/* Hmm? */
	if (count == 0)
		return 0;

	if ((pages = kmalloc(max_pages * sizeof(*pages), GFP_ATOMIC)) == NULL)
		return -ENOMEM;

        /* Try to fault in all of the necessary pages */
	down_read(&current->mm->mmap_sem);
        /* rw==READ means read from drive, write into memory area */
	res = get_user_pages(
		current,
		current->mm,
		uaddr,
		nr_pages,
		rw == READ,
		0, /* don't force */
		pages,
		NULL);
	up_read(&current->mm->mmap_sem);

	/* Errors and no page mapped should return here */
	if (res < nr_pages)
		goto out_unmap;

        for (i=0; i < nr_pages; i++) {
                /* FIXME: flush superflous for rw==READ,
                 * probably wrong function for rw==WRITE
                 */
		flush_dcache_page(pages[i]);
		/* ?? Is locking needed? I don't think so */
		/* if (TestSetPageLocked(pages[i]))
		   goto out_unlock; */
        }

	sg_set_page(sgl, pages[0], 0, uaddr & ~PAGE_MASK);
	if (nr_pages > 1) {
		sgl[0].length = PAGE_SIZE - sgl[0].offset;
		count -= sgl[0].length;
		for (i=1; i < nr_pages ; i++)
			sg_set_page(&sgl[i], pages[i], count < PAGE_SIZE ? count : PAGE_SIZE, 0);
	}
	else {
		sgl[0].length = count;
	}

	kfree(pages);
	return nr_pages;

 out_unmap:
	if (res > 0) {
		for (j=0; j < res; j++)
			page_cache_release(pages[j]);
		res = 0;
	}
	kfree(pages);
	return res;
}


/* And unmap them... */
static int 
st_unmap_user_pages(struct scatterlist *sgl, const unsigned int nr_pages,
		    int dirtied)
{
	int i;

	for (i=0; i < nr_pages; i++) {
		struct page *page = sg_page(&sgl[i]);

		if (dirtied)
			SetPageDirty(page);
		/* unlock_page(page); */
		/* FIXME: cache flush missing for rw==READ
		 * FIXME: call the correct reference counting function
		 */
		page_cache_release(page);
	}

	return 0;
}

/* ^^^^^^^^  above code borrowed from st driver's direct IO ^^^^^^^^^ */
#endif


/* Returns: -ve -> error, 0 -> done, 1 -> try indirect */
static int
sg_build_direct(Sg_request * srp, Sg_fd * sfp, int dxfer_len)
{
#ifdef SG_ALLOW_DIO_CODE
	sg_io_hdr_t *hp = &srp->header;
	Sg_scatter_hold *schp = &srp->data;
	int sg_tablesize = sfp->parentdp->sg_tablesize;
	int mx_sc_elems, res;
	struct scsi_device *sdev = sfp->parentdp->device;

	if (((unsigned long)hp->dxferp &
			queue_dma_alignment(sdev->request_queue)) != 0)
		return 1;

	mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
        if (mx_sc_elems <= 0) {
                return 1;
        }
	res = st_map_user_pages(schp->buffer, mx_sc_elems,
				(unsigned long)hp->dxferp, dxfer_len, 
				(SG_DXFER_TO_DEV == hp->dxfer_direction) ? 1 : 0);
	if (res <= 0) {
		sg_remove_scat(schp);
		return 1;
	}
	schp->k_use_sg = res;
	schp->dio_in_use = 1;
	hp->info |= SG_INFO_DIRECT_IO;
	return 0;
#else
	return 1;
#endif
}

static int
sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size)
{
	struct scatterlist *sg;
	int ret_sz = 0, k, rem_sz, num, mx_sc_elems;
	int sg_tablesize = sfp->parentdp->sg_tablesize;
	int blk_size = buff_size;
	struct page *p = NULL;

	if (blk_size < 0)
		return -EFAULT;
	if (0 == blk_size)
		++blk_size;	/* don't know why */
/* round request up to next highest SG_SECTOR_SZ byte boundary */
	blk_size = (blk_size + SG_SECTOR_MSK) & (~SG_SECTOR_MSK);
	SCSI_LOG_TIMEOUT(4, printk("sg_build_indirect: buff_size=%d, blk_size=%d\n",
				   buff_size, blk_size));

	/* N.B. ret_sz carried into this block ... */
	mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
	if (mx_sc_elems < 0)
		return mx_sc_elems;	/* most likely -ENOMEM */

	num = scatter_elem_sz;
	if (unlikely(num != scatter_elem_sz_prev)) {
		if (num < PAGE_SIZE) {
			scatter_elem_sz = PAGE_SIZE;
			scatter_elem_sz_prev = PAGE_SIZE;
		} else
			scatter_elem_sz_prev = num;
	}
	for (k = 0, sg = schp->buffer, rem_sz = blk_size;
	     (rem_sz > 0) && (k < mx_sc_elems);
	     ++k, rem_sz -= ret_sz, sg = sg_next(sg)) {
		
		num = (rem_sz > scatter_elem_sz_prev) ?
		      scatter_elem_sz_prev : rem_sz;
		p = sg_page_malloc(num, sfp->low_dma, &ret_sz);
		if (!p)
			return -ENOMEM;

		if (num == scatter_elem_sz_prev) {
			if (unlikely(ret_sz > scatter_elem_sz_prev)) {
				scatter_elem_sz = ret_sz;
				scatter_elem_sz_prev = ret_sz;
			}
		}
		sg_set_page(sg, p, (ret_sz > num) ? num : ret_sz, 0);

		SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k=%d, num=%d, "
				 "ret_sz=%d\n", k, num, ret_sz));
	}		/* end of for loop */

	schp->k_use_sg = k;
	SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k_use_sg=%d, "
			 "rem_sz=%d\n", k, rem_sz));

	schp->bufflen = blk_size;
	if (rem_sz > 0)	/* must have failed */
		return -ENOMEM;

	return 0;
}

static int
sg_write_xfer(Sg_request * srp)
{
	sg_io_hdr_t *hp = &srp->header;
	Sg_scatter_hold *schp = &srp->data;
	struct scatterlist *sg = schp->buffer;
	int num_xfer = 0;
	int j, k, onum, usglen, ksglen, res;
	int iovec_count = (int) hp->iovec_count;
	int dxfer_dir = hp->dxfer_direction;
	unsigned char *p;
	unsigned char __user *up;
	int new_interface = ('\0' == hp->interface_id) ? 0 : 1;

	if ((SG_DXFER_UNKNOWN == dxfer_dir) || (SG_DXFER_TO_DEV == dxfer_dir) ||
	    (SG_DXFER_TO_FROM_DEV == dxfer_dir)) {
		num_xfer = (int) (new_interface ? hp->dxfer_len : hp->flags);
		if (schp->bufflen < num_xfer)