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: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
b799bc7da0