dm switch: efficiently support repetitive patterns (56b1ebf2) · Commits · 戴 / test

Documentation/device-mapper/switch.txt

+12 −0

Original line number	Diff line number	Diff line
		@@ -106,6 +106,11 @@ which paths.
		The path number in the range 0 ... (<num_paths> - 1).
		Expressed in hexadecimal (WITHOUT any prefix like 0x).

		R<n>,<m>
		This parameter allows repetitive patterns to be loaded quickly. <n> and <m>
		are hexadecimal numbers. The last <n> mappings are repeated in the next <m>
		slots.

		Status
		======

		@@ -124,3 +129,10 @@ Create a switch device with 64kB region size:
		Set mappings for the first 7 entries to point to devices switch0, switch1,
		switch2, switch0, switch1, switch2, switch1:
		dmsetup message switch 0 set_region_mappings 0:0 :1 :2 :0 :1 :2 :1

		Set repetitive mapping. This command:
		dmsetup message switch 0 set_region_mappings 1000:1 :2 R2,10
		is equivalent to:
		dmsetup message switch 0 set_region_mappings 1000:1 :2 :1 :2 :1 :2 :1 :2 \
		:1 :2 :1 :2 :1 :2 :1 :2 :1 :2

drivers/md/dm-switch.c

+47 −2

Original line number	Diff line number	Diff line
		@@ -380,6 +380,51 @@ static int process_set_region_mappings(struct switch_ctx *sctx,
		unsigned long path_nr;
		const char *string = argv[i];

		if ((*string & 0xdf) == 'R') {
		unsigned long cycle_length, num_write;

		string++;
		if (unlikely(*string == ',')) {
		DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
		return -EINVAL;
		}
		cycle_length = parse_hex(&string);
		if (unlikely(*string != ',')) {
		DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
		return -EINVAL;
		}
		string++;
		if (unlikely(!*string)) {
		DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
		return -EINVAL;
		}
		num_write = parse_hex(&string);
		if (unlikely(*string)) {
		DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
		return -EINVAL;
		}

		if (unlikely(!cycle_length) \|\| unlikely(cycle_length - 1 > region_index)) {
		DMWARN("invalid set_region_mappings cycle length: %lu > %lu",
		cycle_length - 1, region_index);
		return -EINVAL;
		}
		if (unlikely(region_index + num_write < region_index) \|\|
		unlikely(region_index + num_write >= sctx->nr_regions)) {
		DMWARN("invalid set_region_mappings region number: %lu + %lu >= %lu",
		region_index, num_write, sctx->nr_regions);
		return -EINVAL;
		}

		while (num_write--) {
		region_index++;
		path_nr = switch_region_table_read(sctx, region_index - cycle_length);
		switch_region_table_write(sctx, region_index, path_nr);
		}

		continue;
		}

		if (*string == ':')
		region_index++;
		else {
		@@ -508,7 +553,7 @@ static int switch_iterate_devices(struct dm_target *ti,

		static struct target_type switch_target = {
		.name = "switch",
		.version = {1, 0, 0},
		.version = {1, 1, 0},
		.module = THIS_MODULE,
		.ctr = switch_ctr,
		.dtr = switch_dtr,

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