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[dm-devel] [PATCH 23 of 30] DM Exception Store: add arg to prepare_commit



Patch name: dm-exception-store-add-arg-to-prepare_commit.patch

Add the 'group' paramenter to the prepare_exception function.  This
is used to facilitate shared exception stores.  When writing to
a snapshot, an exception is created for only that snapshot (group=0).
When writing to the origin, all snapshots are affected, so rather
than preparing_exceptions for all snapshots one at a time, we can
use the group=1 to indicate that all snapshots managed by the shared
exception store be updated.

Signed-off-by: Jonathan Brassow <jbrassow redhat com>

Index: linux-2.6/drivers/md/dm-exception-store.h
===================================================================
--- linux-2.6.orig/drivers/md/dm-exception-store.h
+++ linux-2.6/drivers/md/dm-exception-store.h
@@ -40,9 +40,14 @@ struct dm_exception_store_type {
 
 	/*
 	 * Find somewhere to store the next exception.
+	 * If the exception store implementation is shared,
+	 * the 'group' field signifies whether to operate on
+	 * the group sharing one exception store, or whether
+	 * to operate on just one of those in the shared
+	 * exception store.
 	 */
 	int (*prepare_exception) (struct dm_exception_store *store,
-				  struct dm_exception *e);
+				  struct dm_exception *e, int group);
 
 	/*
 	 * Update the metadata with this exception.
Index: linux-2.6/drivers/md/dm-snap-persistent.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-snap-persistent.c
+++ linux-2.6/drivers/md/dm-snap-persistent.c
@@ -604,7 +604,7 @@ read_metadata:
 }
 
 static int persistent_prepare_exception(struct dm_exception_store *store,
-					struct dm_exception *e)
+					struct dm_exception *e, int group)
 {
 	struct pstore *ps = get_info(store);
 	uint32_t stride;
Index: linux-2.6/drivers/md/dm-snap-transient.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-snap-transient.c
+++ linux-2.6/drivers/md/dm-snap-transient.c
@@ -50,7 +50,7 @@ static int transient_resume(struct dm_ex
 }
 
 static int transient_prepare_exception(struct dm_exception_store *store,
-				       struct dm_exception *e)
+				       struct dm_exception *e, int group)
 {
 	struct transient_c *tc = store->context;
 	sector_t size = get_dev_size(store->cow->bdev);
Index: linux-2.6/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-snap.c
+++ linux-2.6/drivers/md/dm-snap.c
@@ -833,7 +833,7 @@ static void start_copy(struct dm_snap_pe
  * this.
  */
 static struct dm_snap_pending_exception *
-__find_pending_exception(struct dm_snapshot *s, struct bio *bio)
+__find_pending_exception(struct dm_snapshot *s, struct bio *bio, int group)
 {
 	struct dm_exception *e, *tmp_e;
 	struct dm_snap_pending_exception *pe;
@@ -877,7 +877,7 @@ __find_pending_exception(struct dm_snaps
 	atomic_set(&pe->ref_count, 0);
 	pe->started = 0;
 
-	if (s->store->type->prepare_exception(s->store, &pe->e)) {
+	if (s->store->type->prepare_exception(s->store, &pe->e, group)) {
 		dm_free_exception(s->pending, &pe->e);
 		return NULL;
 	}
@@ -940,7 +940,7 @@ static int snapshot_map(struct dm_target
 	 * writeable.
 	 */
 	if (bio_rw(bio) == WRITE) {
-		pe = __find_pending_exception(s, bio);
+		pe = __find_pending_exception(s, bio, 0);
 		if (!pe) {
 			__invalidate_snapshot(s, -ENOMEM);
 			r = -EIO;
@@ -1120,7 +1120,7 @@ static int __origin_write(struct list_he
 		 */
 		BUG_ON(rtn != -ENOENT);
 
-		pe = __find_pending_exception(snap, bio);
+		pe = __find_pending_exception(snap, bio, 1);
 		if (!pe) {
 			__invalidate_snapshot(snap, -ENOMEM);
 			goto next_snapshot;


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