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Commit b799bc7d authored by Boaz Harrosh's avatar Boaz Harrosh Committed by James Bottomley
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[SCSI] osd_uld: API for retrieving osd devices from Kernel 



Kernel clients like exofs can retrieve struct osd_dev(s)
by means of below API.

+ osduld_path_lookup() - given a path (e.g "/dev/osd0") locks and
returns the corresponding struct osd_dev, which is then needed
for subsequent libosd use.

+ osduld_put_device() - free up use of an osd_dev.

Devices can be shared by multiple clients. The osd_uld_device's
life time is governed by an embedded kref structure.

The osd_uld_device holds an extra reference to both it's
char-device and it's scsi_device, and will release these just
before the final deallocation.

There are three possible lock sources of the osd_uld_device
1. First and for most is the probe() function called by
  scsi-ml upon a successful login into a target. Released in release()
  when logout.
2. Second by user-mode file handles opened on the char-dev.
3. Third is here by Kernel users.
All three locks must be removed before the osd_uld_device is freed.

The MODULE has three lock sources as well:
1. scsi-ml at probe() time, removed after release(). (login/logout)
2. The user-mode file handles open/close.
3. Import symbols by client modules like exofs.

TODO:
  This API is not enough for the pNFS-objects LD. A more versatile
  API will be needed. Proposed API could be:
  struct osd_dev *osduld_sysid_lookup(const char id[OSD_SYSTEMID_LEN]);

Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
parent 95b05a7d

drivers/scsi/osd/osd_uld.c

+63 −0
Original line number Diff line number Diff line
@@ -173,6 +173,69 @@ static const struct file_operations osd_fops = { 
	.unlocked_ioctl = osd_uld_ioctl,

};



struct osd_dev *osduld_path_lookup(const char *path)

{

	struct nameidata nd;

	struct inode *inode;

	struct cdev *cdev;

	struct osd_uld_device *uninitialized_var(oud);

	int error;



	if (!path || !*path) {

		OSD_ERR("Mount with !path || !*path\n");

		return ERR_PTR(-EINVAL);

	}



	error = path_lookup(path, LOOKUP_FOLLOW, &nd);

	if (error) {

		OSD_ERR("path_lookup of %s faild=>%d\n", path, error);

		return ERR_PTR(error);

	}



	inode = nd.path.dentry->d_inode;

	error = -EINVAL; /* Not the right device e.g osd_uld_device */

	if (!S_ISCHR(inode->i_mode)) {

		OSD_DEBUG("!S_ISCHR()\n");

		goto out;

	}



	cdev = inode->i_cdev;

	if (!cdev) {

		OSD_ERR("Before mounting an OSD Based filesystem\n");

		OSD_ERR("  user-mode must open+close the %s device\n", path);

		OSD_ERR("  Example: bash: echo < %s\n", path);

		goto out;

	}



	/* The Magic wand. Is it our char-dev */

	/* TODO: Support sg devices */

	if (cdev->owner != THIS_MODULE) {

		OSD_ERR("Error mounting %s - is not an OSD device\n", path);

		goto out;

	}



	oud = container_of(cdev, struct osd_uld_device, cdev);



	__uld_get(oud);

	error = 0;



out:

	path_put(&nd.path);

	return error ? ERR_PTR(error) : &oud->od;

}

EXPORT_SYMBOL(osduld_path_lookup);



void osduld_put_device(struct osd_dev *od)

{

	if (od) {

		struct osd_uld_device *oud = container_of(od,

						struct osd_uld_device, od);



		__uld_put(oud);

	}

}

EXPORT_SYMBOL(osduld_put_device);



/*

 * Scsi Device operations

 */

include/scsi/osd_initiator.h

+4 −0
Original line number Diff line number Diff line
@@ -33,6 +33,10 @@ struct osd_dev { 
	unsigned def_timeout;

};



/* Retrieve/return osd_dev(s) for use by Kernel clients */

struct osd_dev *osduld_path_lookup(const char *dev_name); /*Use IS_ERR/ERR_PTR*/

void osduld_put_device(struct osd_dev *od);



/* Add/remove test ioctls from external modules */

typedef int (do_test_fn)(struct osd_dev *od, unsigned cmd, unsigned long arg);

int osduld_register_test(unsigned ioctl, do_test_fn *do_test);