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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 05-05-2012, 03:57 AM
Mike Snitzer
 
Default dm stripe: support for non power of 2 chunksize

Non power of 2 chunksize support is needed to properly align stripe IO
on storage that has non power of 2 optimal IO sizes (e.g. RAID6 10+2).

Use do_div wrappers to support non power of 2 chunksize for the pool's
data device. do_div provides comparable performance to the power of 2
math that was performed until now (as tested on modern x86_64 hardware).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
Documentation/device-mapper/striped.txt | 4 +--
drivers/md/dm-stripe.c | 39 +++++++++++---------------------
2 files changed, 16 insertions(+), 27 deletions(-)

Index: linux/Documentation/device-mapper/striped.txt
================================================== =================
--- linux.orig/Documentation/device-mapper/striped.txt
+++ linux/Documentation/device-mapper/striped.txt
@@ -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.
Index: linux/drivers/md/dm-stripe.c
================================================== =================
--- linux.orig/drivers/md/dm-stripe.c
+++ linux/drivers/md/dm-stripe.c
@@ -31,9 +31,7 @@ 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;
@@ -91,7 +89,7 @@ static int get_stripe(struct dm_target *

/*
* 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)
{
@@ -115,21 +113,12 @@ static int stripe_ctr(struct dm_target *
}

chunk_size = simple_strtoul(argv[1], &end, 10);
- if (*end) {
+ if (*end || (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)) {
+ if (dm_do_mod(ti->len, chunk_size)) {
ti->error = "Target length not divisible by "
"chunk size";
return -EINVAL;
@@ -178,8 +167,7 @@ static int stripe_ctr(struct dm_target *
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.
@@ -218,8 +206,8 @@ static void stripe_dtr(struct dm_target
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);
@@ -228,7 +216,7 @@ static void stripe_map_sector(struct str
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,
@@ -239,9 +227,10 @@ static void stripe_map_range_sector(stru
stripe_map_sector(sc, sector, &stripe, result);
if (stripe == target_stripe)
return;
- *result &= ~sc->chunk_mask; /* round down */
+ /* round down */
+ *result = dm_do_div(*result, sc->chunk_size) * 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,
@@ -326,7 +315,7 @@ static int stripe_status(struct dm_targe

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);
@@ -393,7 +382,7 @@ static void stripe_io_hints(struct dm_ta
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);
@@ -421,7 +410,7 @@ static int stripe_merge(struct dm_target

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,

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel
 

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