[PATCH] md: Infrastructure to allow normal IO to continue while array is expanding
We need to allow that different stripes are of different effective sizes, and
use the appropriate size. Also, when a stripe is being expanded, we must
block any IO attempts until the stripe is stable again.
Key elements in this change are:
- each stripe_head gets a 'disk' field which is part of the key,
thus there can sometimes be two stripe heads of the same area of
the array, but covering different numbers of devices. One of these
will be marked STRIPE_EXPANDING and so won't accept new requests.
- conf->expand_progress tracks how the expansion is progressing and
is used to determine whether the target part of the array has been
expanded yet or not.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index b7b2653..6fa274a 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -135,6 +135,7 @@
atomic_t count; /* nr of active thread/requests */
spinlock_t lock;
int bm_seq; /* sequence number for bitmap flushes */
+ int disks; /* disks in stripe */
struct r5dev {
struct bio req;
struct bio_vec vec;
@@ -174,6 +175,7 @@
#define STRIPE_DELAYED 6
#define STRIPE_DEGRADED 7
#define STRIPE_BIT_DELAY 8
+#define STRIPE_EXPANDING 9
/*
* Plugging:
@@ -211,6 +213,10 @@
int raid_disks, working_disks, failed_disks;
int max_nr_stripes;
+ /* used during an expand */
+ sector_t expand_progress; /* MaxSector when no expand happening */
+ int previous_raid_disks;
+
struct list_head handle_list; /* stripes needing handling */
struct list_head delayed_list; /* stripes that have plugged requests */
struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */