[PATCH] md: add write-intent-bitmap support to raid5
Most awkward part of this is delaying write requests until bitmap updates have
been flushed.
To achieve this, we have a sequence number (seq_flush) which is incremented
each time the raid5 is unplugged.
If the raid thread notices that this has changed, it flushes bitmap changes,
and assigned the value of seq_flush to seq_write.
When a write request arrives, it is given the number from seq_write, and that
write request may not complete until seq_flush is larger than the saved seq
number.
We have a new queue for storing stripes which are waiting for a bitmap flush
and an extra flag for stripes to record if the write was 'degraded' and so
should not clear the a bit in the bitmap.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
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 d63ddcb..176fc65 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -134,6 +134,7 @@
unsigned long state; /* state flags */
atomic_t count; /* nr of active thread/requests */
spinlock_t lock;
+ int bm_seq; /* sequence number for bitmap flushes */
struct r5dev {
struct bio req;
struct bio_vec vec;
@@ -165,12 +166,13 @@
/*
* Stripe state
*/
-#define STRIPE_ERROR 1
#define STRIPE_HANDLE 2
#define STRIPE_SYNCING 3
#define STRIPE_INSYNC 4
#define STRIPE_PREREAD_ACTIVE 5
#define STRIPE_DELAYED 6
+#define STRIPE_DEGRADED 7
+#define STRIPE_BIT_DELAY 8
/*
* Plugging:
@@ -210,10 +212,20 @@
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 */
atomic_t preread_active_stripes; /* stripes with scheduled io */
char cache_name[20];
kmem_cache_t *slab_cache; /* for allocating stripes */
+
+ int seq_flush, seq_write;
+ int quiesce;
+
+ int fullsync; /* set to 1 if a full sync is needed,
+ * (fresh device added).
+ * Cleared when a sync completes.
+ */
+
/*
* Free stripes pool
*/