On Mon, 07 Jan 2013 16:09:41 -0600 Jonathan Brassow <jbrassow@xxxxxxxxxx>
wrote:
> DM RAID: Add support for MD's RAID10 "far" and "offset" algorithms
>
> Until now, dm-raid.c only supported the "near" algorthm of MD's RAID10
> implementation. This patch adds support for the "far" and "offset"
> algorithms, but only with the improved redundancy that is brought with
> the introduction of the 'use_far_sets' bit, which shifts copied stripes
> according to smaller sets vs the entire array. That is, the 17th bit
> of the 'layout' variable that defines the RAID10 implementation will
> always be set. (More information on how the 'layout' variable selects
> the RAID10 algorithm can be found in the opening comments of
> drivers/md/raid10.c.)
>
> Signed-off-by: Jonathan Brassow <jbrassow@xxxxxxxxxx>
Applied, pushed out on my for-next branch.
Thanks,
NeilBrown
>
> Index: linux-upstream/Documentation/device-mapper/dm-raid.txt
> ===================================================================
> --- linux-upstream.orig/Documentation/device-mapper/dm-raid.txt
> +++ linux-upstream/Documentation/device-mapper/dm-raid.txt
> @@ -30,6 +30,7 @@ The target is named "raid" and it accept
> raid10 Various RAID10 inspired algorithms chosen by additional params
> - RAID10: Striped Mirrors (aka 'Striping on top of mirrors')
> - RAID1E: Integrated Adjacent Stripe Mirroring
> + - RAID1E: Integrated Offset Stripe Mirroring
> - and other similar RAID10 variants
>
> Reference: Chapter 4 of
> @@ -64,15 +65,15 @@ The target is named "raid" and it accept
> synchronisation state for each region.
>
> [raid10_copies <# copies>]
> - [raid10_format near]
> + [raid10_format <near|far|offset>]
> These two options are used to alter the default layout of
> a RAID10 configuration. The number of copies is can be
> - specified, but the default is 2. There are other variations
> - to how the copies are laid down - the default and only current
> - option is "near". Near copies are what most people think of
> - with respect to mirroring. If these options are left
> - unspecified, or 'raid10_copies 2' and/or 'raid10_format near'
> - are given, then the layouts for 2, 3 and 4 devices are:
> + specified, but the default is 2. There are also three
> + variations to how the copies are laid down - the default
> + is "near". Near copies are what most people think of with
> + respect to mirroring. If these options are left unspecified,
> + or 'raid10_copies 2' and/or 'raid10_format near' are given,
> + then the layouts for 2, 3 and 4 devices are:
> 2 drives 3 drives 4 drives
> -------- ---------- --------------
> A1 A1 A1 A1 A2 A1 A1 A2 A2
> @@ -85,6 +86,33 @@ The target is named "raid" and it accept
> 3-device layout is what might be called a 'RAID1E - Integrated
> Adjacent Stripe Mirroring'.
>
> + If 'raid10_copies 2' and 'raid10_format far', then the layouts
> + for 2, 3 and 4 devices are:
> + 2 drives 3 drives 4 drives
> + -------- -------------- --------------------
> + A1 A2 A1 A2 A3 A1 A2 A3 A4
> + A3 A4 A4 A5 A6 A5 A6 A7 A8
> + A5 A6 A7 A8 A9 A9 A10 A11 A12
> + .. .. .. .. .. .. .. .. ..
> + A2 A1 A3 A1 A2 A2 A1 A4 A3
> + A4 A3 A6 A4 A5 A6 A5 A8 A7
> + A6 A5 A9 A7 A8 A10 A9 A12 A11
> + .. .. .. .. .. .. .. .. ..
> +
> + If 'raid10_copies 2' and 'raid10_format offset', then the
> + layouts for 2, 3 and 4 devices are:
> + 2 drives 3 drives 4 drives
> + -------- ------------ -----------------
> + A1 A2 A1 A2 A3 A1 A2 A3 A4
> + A2 A1 A3 A1 A2 A2 A1 A4 A3
> + A3 A4 A4 A5 A6 A5 A6 A7 A8
> + A4 A3 A6 A4 A5 A6 A5 A8 A7
> + A5 A6 A7 A8 A9 A9 A10 A11 A12
> + A6 A5 A9 A7 A8 A10 A9 A12 A11
> + .. .. .. .. .. .. .. .. ..
> + Here we see layouts closely akin to 'RAID1E - Integrated
> + Offset Stripe Mirroring'.
> +
> <#raid_devs>: The number of devices composing the array.
> Each device consists of two entries. The first is the device
> containing the metadata (if any); the second is the one containing the
> @@ -141,3 +169,5 @@ Version History
> 1.2.0 Handle creation of arrays that contain failed devices.
> 1.3.0 Added support for RAID 10
> 1.3.1 Allow device replacement/rebuild for RAID 10
> +1.4.0 Non-functional change. Removes arg from mapping function.
> +1.4.1 Add RAID10 "far" and "offset" algorithm support.
> Index: linux-upstream/drivers/md/dm-raid.c
> ===================================================================
> --- linux-upstream.orig/drivers/md/dm-raid.c
> +++ linux-upstream/drivers/md/dm-raid.c
> @@ -91,15 +91,44 @@ static struct raid_type {
> {"raid6_nc", "RAID6 (N continue)", 2, 4, 6, ALGORITHM_ROTATING_N_CONTINUE}
> };
>
> +static char *raid10_md_layout_to_format(int layout)
> +{
> + /*
> + * Bit 16 and 17 stand for "offset" and "use_far_sets"
> + * Refer to MD's raid10.c for details
> + */
> + if ((layout & 0x10000) && (layout & 0x20000))
> + return "offset";
> +
> + if ((layout & 0xFF) > 1)
> + return "near";
> +
> + return "far";
> +}
> +
> static unsigned raid10_md_layout_to_copies(int layout)
> {
> - return layout & 0xFF;
> + if ((layout & 0xFF) > 1)
> + return layout & 0xFF;
> + return (layout >> 8) & 0xFF;
> }
>
> static int raid10_format_to_md_layout(char *format, unsigned copies)
> {
> - /* 1 "far" copy, and 'copies' "near" copies */
> - return (1 << 8) | (copies & 0xFF);
> + unsigned n = 1, f = 1;
> +
> + if (!strcmp("near", format))
> + n = copies;
> + else
> + f = copies;
> +
> + if (!strcmp("offset", format))
> + return 0x30000 | (f << 8) | n;
> +
> + if (!strcmp("far", format))
> + return 0x20000 | (f << 8) | n;
> +
> + return (f << 8) | n;
> }
>
> static struct raid_type *get_raid_type(char *name)
> @@ -352,6 +381,7 @@ static int validate_rebuild_devices(stru
> {
> unsigned i, rebuild_cnt = 0;
> unsigned rebuilds_per_group, copies, d;
> + unsigned group_size, last_group_start;
>
> if (!(rs->print_flags & DMPF_REBUILD))
> return 0;
> @@ -381,9 +411,6 @@ static int validate_rebuild_devices(stru
> * as long as the failed devices occur in different mirror
> * groups (i.e. different stripes).
> *
> - * Right now, we only allow for "near" copies. When other
> - * formats are added, we will have to check those too.
> - *
> * When checking "near" format, make sure no adjacent devices
> * have failed beyond what can be handled. In addition to the
> * simple case where the number of devices is a multiple of the
> @@ -394,13 +421,39 @@ static int validate_rebuild_devices(stru
> * C D D E E
> */
> rebuilds_per_group = 0;
> - for (i = 0; i < rs->md.raid_disks * copies; i++) {
> - d = i % rs->md.raid_disks;
> - if (!test_bit(In_sync, &rs->dev[d].rdev.flags) &&
> - (++rebuilds_per_group >= copies))
> - goto too_many;
> - if (!((i + 1) % copies))
> + if (!strcmp("near", raid10_md_layout_to_format(rs->md.layout))) {
> + for (i = 0; i < rs->md.raid_disks * copies; i++) {
> + d = i % rs->md.raid_disks;
> + if (!test_bit(In_sync, &rs->dev[d].rdev.flags) &&
> + (++rebuilds_per_group >= copies))
> + goto too_many;
> + if (!((i + 1) % copies))
> + rebuilds_per_group = 0;
> + }
> + break;
> + }
> +
> + /*
> + * When checking "far" and "offset" formats, we need to ensure
> + * that the device that holds its copy is not also dead or
> + * being rebuilt. (Note that "far" and "offset" formats only
> + * support two copies right now. These formats also only ever
> + * use the 'use_far_sets' variant.)
> + *
> + * This check is somewhat complicated by the need to account
> + * for arrays that are not a multiple of (far) copies. This
> + * results in the need to treat the last (potentially larger)
> + * set differently.
> + */
> + group_size = (rs->md.raid_disks / copies);
> + last_group_start = (rs->md.raid_disks / group_size) - 1;
> + last_group_start *= group_size;
> + for (i = 0; i < rs->md.raid_disks; i++) {
> + if (!(i % copies) && !(i > last_group_start))
> rebuilds_per_group = 0;
> + if (!test_bit(In_sync, &rs->dev[i].rdev.flags) &&
> + (++rebuilds_per_group >= copies))
> + goto too_many;
> }
> break;
> default:
> @@ -438,7 +491,7 @@ too_many:
> *
> * RAID10-only options:
> * [raid10_copies <# copies>] Number of copies. (Default: 2)
> - * [raid10_format <near>] Layout algorithm. (Default: near)
> + * [raid10_format <near|far|offset>] Layout algorithm. (Default: near)
> */
> static int parse_raid_params(struct raid_set *rs, char **argv,
> unsigned num_raid_params)
> @@ -525,7 +578,9 @@ static int parse_raid_params(struct raid
> rs->ti->error = "'raid10_format' is an invalid parameter for this RAID type";
> return -EINVAL;
> }
> - if (strcmp("near", argv[i])) {
> + if (strcmp("near", argv[i]) &&
> + strcmp("far", argv[i]) &&
> + strcmp("offset", argv[i])) {
> rs->ti->error = "Invalid 'raid10_format' value given";
> return -EINVAL;
> }
> @@ -649,6 +704,15 @@ static int parse_raid_params(struct raid
> return -EINVAL;
> }
>
> + /*
> + * If the format is not "near", we only support
> + * two copies at the moment.
> + */
> + if (strcmp("near", raid10_format) && (raid10_copies > 2)) {
> + rs->ti->error = "Too many copies for given RAID10 format.";
> + return -EINVAL;
> + }
> +
> /* (Len * #mirrors) / #devices */
> sectors_per_dev = rs->ti->len * raid10_copies;
> sector_div(sectors_per_dev, rs->md.raid_disks);
> @@ -862,17 +926,30 @@ static int super_init_validation(struct
> /*
> * Reshaping is not currently allowed
> */
> - if ((le32_to_cpu(sb->level) != mddev->level) ||
> - (le32_to_cpu(sb->layout) != mddev->layout) ||
> - (le32_to_cpu(sb->stripe_sectors) != mddev->chunk_sectors)) {
> - DMERR("Reshaping arrays not yet supported.");
> + if (le32_to_cpu(sb->level) != mddev->level) {
> + DMERR("Reshaping arrays not yet supported. (RAID level change)");
> + return -EINVAL;
> + }
> + if (le32_to_cpu(sb->layout) != mddev->layout) {
> + DMERR("Reshaping arrays not yet supported. (RAID layout change)");
> + DMERR(" 0x%X vs 0x%X", le32_to_cpu(sb->layout), mddev->layout);
> + DMERR(" Old layout: %s w/ %d copies",
> + raid10_md_layout_to_format(le32_to_cpu(sb->layout)),
> + raid10_md_layout_to_copies(le32_to_cpu(sb->layout)));
> + DMERR(" New layout: %s w/ %d copies",
> + raid10_md_layout_to_format(mddev->layout),
> + raid10_md_layout_to_copies(mddev->layout));
> + return -EINVAL;
> + }
> + if (le32_to_cpu(sb->stripe_sectors) != mddev->chunk_sectors) {
> + DMERR("Reshaping arrays not yet supported. (stripe sectors change)");
> return -EINVAL;
> }
>
> /* We can only change the number of devices in RAID1 right now */
> if ((rs->raid_type->level != 1) &&
> (le32_to_cpu(sb->num_devices) != mddev->raid_disks)) {
> - DMERR("Reshaping arrays not yet supported.");
> + DMERR("Reshaping arrays not yet supported. (device count change)");
> return -EINVAL;
> }
>
> @@ -1356,7 +1433,8 @@ static int raid_status(struct dm_target
> raid10_md_layout_to_copies(rs->md.layout));
>
> if (rs->print_flags & DMPF_RAID10_FORMAT)
> - DMEMIT(" raid10_format near");
> + DMEMIT(" raid10_format %s",
> + raid10_md_layout_to_format(rs->md.layout));
>
> DMEMIT(" %d", rs->md.raid_disks);
> for (i = 0; i < rs->md.raid_disks; i++) {
> @@ -1432,7 +1510,7 @@ static void raid_resume(struct dm_target
>
> static struct target_type raid_target = {
> .name = "raid",
> - .version = {1, 4, 0},
> + .version = {1, 4, 1},
> .module = THIS_MODULE,
> .ctr = raid_ctr,
> .dtr = raid_dtr,
> @@ -1447,6 +1525,10 @@ static struct target_type raid_target =
>
> static int __init dm_raid_init(void)
> {
> + DMINFO("Loading target version %u.%u.%u",
> + raid_target.version[0],
> + raid_target.version[1],
> + raid_target.version[2]);
> return dm_register_target(&raid_target);
> }
>
>
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