[PATCH 06/16] osd_uld: API for retrieving osd devices from Kernel

Boaz Harrosh
2009-01-25T14:58:07Z

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>
---
drivers/scsi/osd/osd_uld.c | 63 ++++++++++++++++++++++++++++++++++++++++++
include/scsi/osd_initiator.h | 4 ++
2 files changed, 67 insertions(+), 0 deletions(-)

diff --git a/drivers/scsi/osd/osd_uld.c b/drivers/scsi/osd/osd_uld.c
index f6f9a99..cd4ca7c 100644
--- a/drivers/scsi/osd/osd_uld.c
+++ b/drivers/scsi/osd/osd_uld.c
@@ -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
*/
diff --git a/include/scsi/osd_initiator.h b/include/scsi/osd_initiator.h
index a5dbbdd..e84dc7a 100644
--- a/include/scsi/osd_initiator.h
+++ b/include/scsi/osd_initiator.h
@@ -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);
--
1.6.0.1