[dm-devel] [Patch 7 of 14] Device Mapper Mirror

[Jonathan Brassow]

 brassow

This patch adds the ability to specify desired features in the mirror
constructor/mapping table.

The first feature of interest is "handle_errors".  Currently, mirroring
will ignore any I/O errors from the devices.  Subsequent patches will
check for this flag and handle the errors.  If flag/feature is not
present, mirror will do nothing - maintaining backwards compatibility.

Index: linux-2.6.18.1/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.18.1.orig/drivers/md/dm-raid1.c	2006-11-01 14:16:14.000000000 -0600
+++ linux-2.6.18.1/drivers/md/dm-raid1.c	2006-11-01 14:16:15.000000000 -0600
@@ -114,6 +114,8 @@ struct region {
 /*-----------------------------------------------------------------
  * Mirror set structures.
  *---------------------------------------------------------------*/
+#define DM_FEATURE_HANDLE_ERRORS 0x1
+
 struct mirror {
 	atomic_t error_count;
 	struct dm_dev *dev;
@@ -130,6 +132,9 @@ struct mirror_set {
 	struct bio_list reads;
 	struct bio_list writes;
 
+	/* Features */
+	uint64_t feature_flags;
+
 	/* recovery */
 	region_t nr_regions;
 	int in_sync;
@@ -1037,14 +1042,63 @@ static struct dirty_log *create_dirty_lo
 	return dl;
 }
 
+static int parse_features(struct mirror_set *ms,
+			  unsigned int argc, char **argv,
+			  unsigned int *args_used)
+{
+	int i;
+	unsigned int features_argc, used = 0;
+	struct dm_target *ti = ms->ti;
+
+	*args_used = 0;
+
+	if (!argc)
+		return 0;
+
+	if (sscanf(argv[0], "%u", &features_argc) != 1) {
+		ti->error = "Invalid number of features";
+		return -EINVAL;
+	}
+
+	argc--;
+	argv++;
+	used++;
+
+	if (features_argc > argc) {
+		ti->error = "Not enough arguments to support feature count";
+		return -EINVAL;
+	}
+
+	for (i = 0; i < features_argc; i++) {
+		if (!strcmp("handle_errors", argv[i]))
+			ms->feature_flags |= DM_FEATURE_HANDLE_ERRORS;
+		else {
+			ti->error = "Unknown feature argument";
+			return -EINVAL;
+		}
+		used++;
+	}
+
+	*args_used = used;
+	return 0;
+}
+
 /*
- * Construct a mirror mapping:
+ * mirror_ctr
+ * @ti
+ * @argc
+ * @argv
  *
- * log_type #log_params <log_params>
- * #mirrors [mirror_path offset]{2,}
+ * Allowable argument list is as follows:
+ *     log_type #log_params <log_params> \
+ *     #mirrors <device1> <offset1> ... <deviceN> <offsetN> \
+ *     <# feature args> <feature args>
  *
- * log_type is "core" or "disk"
- * #log_params is between 1 and 3
+ * Refer to log implementation for log specific parameters.
+ * Current features include:
+ *     handle_errors
+ *
+ * Returns: 0 on success, -EXXX on failure
  */
 #define DM_IO_PAGES 64
 static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
@@ -1096,6 +1150,22 @@ static int mirror_ctr(struct dm_target *
 	ti->private = ms;
  	ti->split_io = ms->rh.region_size;
 
+	/* check for features */
+	r = parse_features(ms, argc, argv, &args_used);
+	if (r) {
+		free_context(ms, ti, ms->nr_mirrors);
+		return r;
+	}
+
+	argv += args_used;
+	argc -= args_used;
+
+	if (argc) {
+		ti->error = "Wrong number of mirror arguments";
+		free_context(ms, ti, ms->nr_mirrors);
+		return -EINVAL;
+	}
+
 	r = kcopyd_client_create(DM_IO_PAGES, &ms->kcopyd_client);
 	if (r) {
 		free_context(ms, ti, ms->nr_mirrors);
@@ -1243,6 +1313,9 @@ static int mirror_status(struct dm_targe
 		for (m = 0; m < ms->nr_mirrors; m++)
 			DMEMIT(" %s %llu", ms->mirror[m].dev->name,
 				(unsigned long long)ms->mirror[m].offset);
+
+		if (ms->feature_flags & DM_FEATURE_HANDLE_ERRORS)
+			DMEMIT(" 1 handle_errors");
 	}
 
 	return 0;