Date: Thu, 21 Sep 2006 16:46:30 +0100
From: Alasdair G Kergon <agk@redhat.com>
Subject: [RHEL5 PATCH 10/30] dm snapshot: make read and write exception functions void

read_exception() and write_exception() only return an error if
supplied with an out-of-range index.  If this ever happens it's the
result of a bug in the calling code so we handle this with an
assertion and remove the error handling in the callers.

Index: linux-2.6.18.noarch/drivers/md/dm-exception-store.c
===================================================================
--- linux-2.6.18.noarch.orig/drivers/md/dm-exception-store.c
+++ linux-2.6.18.noarch/drivers/md/dm-exception-store.c
@@ -296,42 +296,29 @@ static int write_header(struct pstore *p
  */
 static struct disk_exception *get_exception(struct pstore *ps, uint32_t index)
 {
-	if (index >= ps->exceptions_per_area)
-		return NULL;
+	BUG_ON(index >= ps->exceptions_per_area);
 
 	return ((struct disk_exception *) ps->area) + index;
 }
 
-static int read_exception(struct pstore *ps,
-			  uint32_t index, struct disk_exception *result)
+static void read_exception(struct pstore *ps,
+			   uint32_t index, struct disk_exception *result)
 {
-	struct disk_exception *e;
-
-	e = get_exception(ps, index);
-	if (!e)
-		return -EINVAL;
+	struct disk_exception *e = get_exception(ps, index);
 
 	/* copy it */
 	result->old_chunk = le64_to_cpu(e->old_chunk);
 	result->new_chunk = le64_to_cpu(e->new_chunk);
-
-	return 0;
 }
 
-static int write_exception(struct pstore *ps,
-			   uint32_t index, struct disk_exception *de)
+static void write_exception(struct pstore *ps,
+			    uint32_t index, struct disk_exception *de)
 {
-	struct disk_exception *e;
-
-	e = get_exception(ps, index);
-	if (!e)
-		return -EINVAL;
+	struct disk_exception *e = get_exception(ps, index);
 
 	/* copy it */
 	e->old_chunk = cpu_to_le64(de->old_chunk);
 	e->new_chunk = cpu_to_le64(de->new_chunk);
-
-	return 0;
 }
 
 /*
@@ -349,10 +336,7 @@ static int insert_exceptions(struct psto
 	*full = 1;
 
 	for (i = 0; i < ps->exceptions_per_area; i++) {
-		r = read_exception(ps, i, &de);
-
-		if (r)
-			return r;
+		read_exception(ps, i, &de);
 
 		/*
 		 * If the new_chunk is pointing at the start of

Date: Thu, 21 Sep 2006 16:46:48 +0100
From: Alasdair G Kergon <agk@redhat.com>
Subject: [RHEL5 PATCH 11/30] dm snapshot: fix metadata writing when suspending

When suspending a device-mapper device, dm_suspend() sleeps until all
necessary I/O is completed.  This state is triggered by a callback from
persistent_commit().  But some I/O can still be issued *after* the
callback (to prepare the next metadata area for use if the current one is
full).  This patch delays the callback until after that I/O is complete.

Index: linux-2.6.18.noarch/drivers/md/dm-exception-store.c
===================================================================
--- linux-2.6.18.noarch.orig/drivers/md/dm-exception-store.c
+++ linux-2.6.18.noarch/drivers/md/dm-exception-store.c
@@ -536,6 +536,16 @@ static void persistent_commit(struct exc
 		if (r)
 			ps->valid = 0;
 
+		/*
+		 * Have we completely filled the current area ?
+		 */
+		if (ps->current_committed == ps->exceptions_per_area) {
+			ps->current_committed = 0;
+			r = zero_area(ps, ps->current_area + 1);
+			if (r)
+				ps->valid = 0;
+		}
+
 		for (i = 0; i < ps->callback_count; i++) {
 			cb = ps->callbacks + i;
 			cb->callback(cb->context, r == 0 ? 1 : 0);
@@ -543,16 +553,6 @@ static void persistent_commit(struct exc
 
 		ps->callback_count = 0;
 	}
-
-	/*
-	 * Have we completely filled the current area ?
-	 */
-	if (ps->current_committed == ps->exceptions_per_area) {
-		ps->current_committed = 0;
-		r = zero_area(ps, ps->current_area + 1);
-		if (r)
-			ps->valid = 0;
-	}
 }
 
 static void persistent_drop(struct exception_store *store)