ore: Support for partial component table
Users like the objlayout-driver would like to only pass
a partial device table that covers the IO in question.
For example exofs divides the file into raid-group-sized
chunks and only serves group_width number of devices at
a time.
The partiality is communicated by setting
ore_componets->first_dev and the array covers all logical
devices from oc->first_dev upto (oc->first_dev + oc->numdevs)
The ore_comp_dev() API receives a logical device index
and returns the actual present device in the table.
An out-of-range dev_index will BUG.
Logical device index is the theoretical device index as if
all the devices of a file are present. .i.e:
total_devs = group_width * mirror_p1 * group_count
0 <= dev_index < total_devs
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
diff --git a/fs/exofs/exofs.h b/fs/exofs/exofs.h
index 006fd6f..51f4b4c 100644
--- a/fs/exofs/exofs.h
+++ b/fs/exofs/exofs.h
@@ -217,6 +217,7 @@
one_comp->obj.id = oid;
exofs_make_credential(one_comp->cred, &one_comp->obj);
+ oc->first_dev = 0;
oc->numdevs = sbi->layout.group_width * sbi->layout.mirrors_p1 *
sbi->layout.group_count;
oc->single_comp = EC_SINGLE_COMP;