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dm stripe: support for non power of 2 chunksize 

Support non-power-of-2 chunk sizes with dm striping for proper alignment
of stripe IO on storage that has non-power-of-2 optimal IO sizes (e.g.
RAID6 10+2).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mike Snitzer 2012-07-27 15:08:01 +01:00 committed by Alasdair G Kergon
parent 542f903814
commit eb850de608
2 changed files with 21 additions and 27 deletions
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4
Documentation/device-mapper/striped.txt
View File

@ -9,8 +9,8 @@ devices in parallel.
Parameters: <num devs> <chunk size> [<dev path> <offset>]+
<num devs>: Number of underlying devices.
<chunk size>: Size of each chunk of data. Must be a power-of-2 and at
least as large as the system's PAGE_SIZE.
<chunk size>: Size of each chunk of data. Must be at least as
large as the system's PAGE_SIZE.
<dev path>: Full pathname to the underlying block-device, or a
"major:minor" device-number.
<offset>: Starting sector within the device.

44
drivers/md/dm-stripe.c
View File

@ -30,9 +30,7 @@ struct stripe_c {
/* The size of this target / num. stripes */
sector_t stripe_width;
/* stripe chunk size */
uint32_t chunk_shift;
sector_t chunk_mask;
uint32_t chunk_size;
/* Needed for handling events */
struct dm_target *ti;
@ -90,7 +88,7 @@ static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
/*
* Construct a striped mapping.
* <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
* <number of stripes> <chunk size> [<dev_path> <offset>]+
*/
static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
@ -111,21 +109,14 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
return -EINVAL;
}
if (kstrtouint(argv[1], 10, &chunk_size)) {
if (kstrtouint(argv[1], 10, &chunk_size) ||
(chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
ti->error = "Invalid chunk_size";
return -EINVAL;
}
/*
* chunk_size is a power of two
*/
if (!is_power_of_2(chunk_size) ||
(chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
ti->error = "Invalid chunk size";
return -EINVAL;
}
if (ti->len & (chunk_size - 1)) {
width = ti->len;
if (sector_div(width, chunk_size)) {
ti->error = "Target length not divisible by "
"chunk size";
return -EINVAL;
@ -172,8 +163,7 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->num_flush_requests = stripes;
ti->num_discard_requests = stripes;
sc->chunk_shift = ffs(chunk_size) - 1;
sc->chunk_mask = ((sector_t) chunk_size) - 1;
sc->chunk_size = chunk_size;
/*
* Get the stripe destinations.
@ -212,8 +202,8 @@ static void stripe_dtr(struct dm_target *ti)
static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
uint32_t *stripe, sector_t *result)
{
sector_t offset = dm_target_offset(sc->ti, sector);
sector_t chunk = offset >> sc->chunk_shift;
sector_t chunk = dm_target_offset(sc->ti, sector);
sector_t chunk_offset = sector_div(chunk, sc->chunk_size);
if (sc->stripes_shift < 0)
*stripe = sector_div(chunk, sc->stripes);
@ -222,7 +212,7 @@ static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
chunk >>= sc->stripes_shift;
}
*result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);
*result = (chunk * sc->chunk_size) + chunk_offset;
}
static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
@ -233,9 +223,13 @@ static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
stripe_map_sector(sc, sector, &stripe, result);
if (stripe == target_stripe)
return;
*result &= ~sc->chunk_mask; /* round down */
/* round down */
sector = *result;
*result -= sector_div(sector, sc->chunk_size);
if (target_stripe < stripe)
*result += sc->chunk_mask + 1; /* next chunk */
*result += sc->chunk_size; /* next chunk */
}
static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
@ -320,7 +314,7 @@ static int stripe_status(struct dm_target *ti,
case STATUSTYPE_TABLE:
DMEMIT("%d %llu", sc->stripes,
(unsigned long long)sc->chunk_mask + 1);
(unsigned long long)sc->chunk_size);
for (i = 0; i < sc->stripes; i++)
DMEMIT(" %s %llu", sc->stripe[i].dev->name,
(unsigned long long)sc->stripe[i].physical_start);
@ -387,7 +381,7 @@ static void stripe_io_hints(struct dm_target *ti,
struct queue_limits *limits)
{
struct stripe_c *sc = ti->private;
unsigned chunk_size = (sc->chunk_mask + 1) << 9;
unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;
blk_limits_io_min(limits, chunk_size);
blk_limits_io_opt(limits, chunk_size * sc->stripes);
@ -415,7 +409,7 @@ static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
static struct target_type stripe_target = {
.name = "striped",
.version = {1, 4, 0},
.version = {1, 5, 0},
.module = THIS_MODULE,
.ctr = stripe_ctr,
.dtr = stripe_dtr,