ore/exofs: Change the type of the devices array (API change)

In the pNFS obj-LD the device table at the layout level needs
to point to a device_cache node, where it is possible and likely
that many layouts will point to the same device-nodes.

In Exofs we have a more orderly structure where we have a single
array of devices that repeats twice for a round-robin view of the
device table

This patch moves to a model that can be used by the pNFS obj-LD
where struct ore_components holds an array of ore_dev-pointers.
(ore_dev is newly defined and contains a struct osd_dev *od
 member)

Each pointer in the array of pointers will point to a bigger
user-defined dev_struct. That can be accessed by use of the
container_of macro.

In Exofs an __alloc_dev_table() function allocates the
ore_dev-pointers array as well as an exofs_dev array, in one
allocation and does the addresses dance to set everything pointing
correctly. It still keeps the double allocation trick for the
inodes round-robin view of the table.

The device table is always allocated dynamically, also for the
single device case. So it is unconditionally freed at umount.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

1 files changed, 25 insertions, 1 deletions

diff --git a/include/scsi/osd_ore.h b/include/scsi/osd_ore.h
index e4d550faa7c9..8fefdfbb1ced 100644
--- a/include/scsi/osd_ore.h
+++ b/include/scsi/osd_ore.h
@@ -44,6 +44,10 @@ struct ore_layout {
 	unsigned group_count;
 };
 
+struct ore_dev {
+	struct osd_dev *od;
+};
+
 struct ore_components {
 	unsigned	numdevs;		/* Num of devices in array    */
 	/* If @single_comp == EC_SINGLE_COMP, @comps points to a single
@@ -53,9 +57,29 @@ struct ore_components {
 		EC_SINGLE_COMP = 0, EC_MULTPLE_COMPS = 0xffffffff
 	}		single_comp;
 	struct ore_comp	*comps;
-	struct osd_dev	**ods;			/* osd_dev array              */
+
+	/* Array of pointers to ore_dev-* . User will usually have these pointed
+	 * too a bigger struct which contain an "ore_dev ored" member and use
+	 * container_of(oc->ods[i], struct foo_dev, ored) to access the bigger
+	 * structure.
+	 */
+	struct ore_dev	**ods;
 };
 
+/* ore_comp_dev Recievies a logical device index */
+static inline struct osd_dev *ore_comp_dev(
+	const struct ore_components *oc, unsigned i)
+{
+	BUG_ON(oc->numdevs <= i);
+	return oc->ods[i]->od;
+}
+
+static inline void ore_comp_set_dev(
+	struct ore_components *oc, unsigned i, struct osd_dev *od)
+{
+	oc->ods[i]->od = od;
+}
+
 struct ore_striping_info {
 	u64 obj_offset;
 	u64 group_length;