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Commit 56b1ebf2 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm switch: efficiently support repetitive patterns 



Add support for quickly loading a repetitive pattern into the
dm-switch target.

In the "set_regions_mappings" message, the user may now use "Rn,m" as
one of the arguments.  "n" and "m" are hexadecimal numbers.  The "Rn,m"
argument repeats the last "n" arguments in the following "m" slots.

For example:
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

Requested-by: default avatarJay Wang <jwang@nimblestorage.com>
Tested-by: default avatarJay Wang <jwang@nimblestorage.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 99eb1908

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,