exofs:  Add SYSFS info for autologin/pNFS export

Introduce sysfs infrastructure for exofs cluster filesystem.

Each OSD target shows up as below in the sysfs hierarchy:
	/sys/fs/exofs/<osdname>_<partition_id>/devX

Where <osdname>_<partition_id> is the unique identification
of a Superblock.

Where devX: 0 <= X < device_table_size. They are ordered
in device-table order as specified to the mkfs.exofs command

Each OSD device  devX has following attributes :
	osdname - ReadOnly
	systemid - ReadOnly
	uri - Read/Write

It is up to user-mode to update devX/uri for support of
autologin.

These sysfs information are used both for autologin as well
as support for exporting exofs via a pNFSD server in user-mode.
(.eg NFS-Ganesha)

Signed-off-by: Sachin Bhamare <sbhamare@panasas.com>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
diff --git a/fs/exofs/super.c b/fs/exofs/super.c
index 59e0849..4337836 100644
--- a/fs/exofs/super.c
+++ b/fs/exofs/super.c
@@ -472,6 +472,7 @@
 	_exofs_print_device("Unmounting", NULL, ore_comp_dev(&sbi->oc, 0),
 			    sbi->one_comp.obj.partition);
 
+	exofs_sysfs_sb_del(sbi);
 	bdi_destroy(&sbi->bdi);
 	exofs_free_sbi(sbi);
 	sb->s_fs_info = NULL;
@@ -632,6 +633,12 @@
 	memcpy(&sbi->oc.ods[numdevs], &sbi->oc.ods[0],
 		(numdevs - 1) * sizeof(sbi->oc.ods[0]));
 
+	/* create sysfs subdir under which we put the device table
+	 * And cluster layout. A Superblock is identified by the string:
+	 *	"dev[0].osdname"_"pid"
+	 */
+	exofs_sysfs_sb_add(sbi, &dt->dt_dev_table[0]);
+
 	for (i = 0; i < numdevs; i++) {
 		struct exofs_fscb fscb;
 		struct osd_dev_info odi;
@@ -657,6 +664,7 @@
 			eds[i].ored.od = fscb_od;
 			++sbi->oc.numdevs;
 			fscb_od = NULL;
+			exofs_sysfs_odev_add(&eds[i], sbi);
 			continue;
 		}
 
@@ -682,6 +690,7 @@
 				  odi.osdname);
 			goto out;
 		}
+		exofs_sysfs_odev_add(&eds[i], sbi);
 
 		/* TODO: verify other information is correct and FS-uuid
 		 *	 matches. Benny what did you say about device table
@@ -844,6 +853,7 @@
 		goto free_sbi;
 	}
 
+	exofs_sysfs_dbg_print();
 	_exofs_print_device("Mounting", opts->dev_name,
 			    ore_comp_dev(&sbi->oc, 0),
 			    sbi->one_comp.obj.partition);
@@ -1023,6 +1033,9 @@
 	if (err)
 		goto out_d;
 
+	/* We don't fail if sysfs creation failed */
+	exofs_sysfs_init();
+
 	return 0;
 out_d:
 	destroy_inodecache();
@@ -1032,6 +1045,7 @@
 
 static void __exit exit_exofs(void)
 {
+	exofs_sysfs_uninit();
 	unregister_filesystem(&exofs_type);
 	destroy_inodecache();
 }