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dm thin: support for non power of 2 pool blocksize

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

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

The kernel currently assumes that limits->discard_granularity is a power
of two so the thin target only enables discard support if the block
size is a power of two.

Eliminate pool structure's 'block_shift', 'offset_mask' and
remaining 4 byte holes.

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 15:08:02 +01:00 committed by Alasdair G Kergon
parent 33d07c0dfa
commit 55f2b8bdb0
1 changed files with 37 additions and 22 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

59
drivers/md/dm-thin.c
View file

@ -510,10 +510,8 @@ struct pool {
struct block_device *md_dev;
struct dm_pool_metadata *pmd;
uint32_t sectors_per_block;
unsigned block_shift;
dm_block_t offset_mask;
dm_block_t low_water_blocks;
uint32_t sectors_per_block;
struct pool_features pf;
unsigned low_water_triggered:1; /* A dm event has been sent */
@ -526,8 +524,8 @@ struct pool {
struct work_struct worker;
struct delayed_work waker;
unsigned ref_count;
unsigned long last_commit_jiffies;
unsigned ref_count;
spinlock_t lock;
struct bio_list deferred_bios;
@ -679,16 +677,21 @@ static void requeue_io(struct thin_c *tc)
static dm_block_t get_bio_block(struct thin_c *tc, struct bio *bio)
{
return bio->bi_sector >> tc->pool->block_shift;
sector_t block_nr = bio->bi_sector;
(void) sector_div(block_nr, tc->pool->sectors_per_block);
return block_nr;
}
static void remap(struct thin_c *tc, struct bio *bio, dm_block_t block)
{
struct pool *pool = tc->pool;
sector_t bi_sector = bio->bi_sector;
bio->bi_bdev = tc->pool_dev->bdev;
bio->bi_sector = (block << pool->block_shift) +
(bio->bi_sector & pool->offset_mask);
bio->bi_sector = (block * pool->sectors_per_block) +
sector_div(bi_sector, pool->sectors_per_block);
}
static void remap_to_origin(struct thin_c *tc, struct bio *bio)
@ -933,9 +936,10 @@ static void process_prepared(struct pool *pool, struct list_head *head,
*/
static int io_overlaps_block(struct pool *pool, struct bio *bio)
{
return !(bio->bi_sector & pool->offset_mask) &&
(bio->bi_size == (pool->sectors_per_block << SECTOR_SHIFT));
sector_t bi_sector = bio->bi_sector;
return !sector_div(bi_sector, pool->sectors_per_block) &&
(bio->bi_size == (pool->sectors_per_block << SECTOR_SHIFT));
}
static int io_overwrites_block(struct pool *pool, struct bio *bio)
@ -1239,8 +1243,8 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
* part of the discard that is in a subsequent
* block.
*/
sector_t offset = bio->bi_sector - (block << pool->block_shift);
unsigned remaining = (pool->sectors_per_block - offset) << 9;
sector_t offset = bio->bi_sector - (block * pool->sectors_per_block);
unsigned remaining = (pool->sectors_per_block - offset) << SECTOR_SHIFT;
bio->bi_size = min(bio->bi_size, remaining);
cell_release_singleton(cell, bio);
@ -1722,8 +1726,6 @@ static struct pool *pool_create(struct mapped_device *pool_md,
pool->pmd = pmd;
pool->sectors_per_block = block_size;
pool->block_shift = ffs(block_size) - 1;
pool->offset_mask = block_size - 1;
pool->low_water_blocks = 0;
pool_features_init(&pool->pf);
pool->prison = prison_create(PRISON_CELLS);
@ -1971,7 +1973,7 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
if (kstrtoul(argv[2], 10, &block_size) || !block_size ||
block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS ||
!is_power_of_2(block_size)) {
block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
ti->error = "Invalid block size";
r = -EINVAL;
goto out;
@ -2018,6 +2020,15 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
goto out_flags_changed;
}
/*
* The block layer requires discard_granularity to be a power of 2.
*/
if (pf.discard_enabled && !is_power_of_2(block_size)) {
ti->error = "Discard support must be disabled when the block size is not a power of 2";
r = -EINVAL;
goto out_flags_changed;
}
pt->pool = pool;
pt->ti = ti;
pt->metadata_dev = metadata_dev;
@ -2097,7 +2108,8 @@ static int pool_preresume(struct dm_target *ti)
int r;
struct pool_c *pt = ti->private;
struct pool *pool = pt->pool;
dm_block_t data_size, sb_data_size;
sector_t data_size = ti->len;
dm_block_t sb_data_size;
/*
* Take control of the pool object.
@ -2106,7 +2118,8 @@ static int pool_preresume(struct dm_target *ti)
if (r)
return r;
data_size = ti->len >> pool->block_shift;
(void) sector_div(data_size, pool->sectors_per_block);
r = dm_pool_get_data_dev_size(pool->pmd, &sb_data_size);
if (r) {
DMERR("failed to retrieve data device size");
@ -2115,7 +2128,7 @@ static int pool_preresume(struct dm_target *ti)
if (data_size < sb_data_size) {
DMERR("pool target too small, is %llu blocks (expected %llu)",
data_size, sb_data_size);
(unsigned long long)data_size, sb_data_size);
return -EINVAL;
} else if (data_size > sb_data_size) {
@ -2764,19 +2777,21 @@ static int thin_status(struct dm_target *ti, status_type_t type,
static int thin_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
dm_block_t blocks;
sector_t blocks;
struct thin_c *tc = ti->private;
struct pool *pool = tc->pool;
/*
* We can't call dm_pool_get_data_dev_size() since that blocks. So
* we follow a more convoluted path through to the pool's target.
*/
if (!tc->pool->ti)
if (!pool->ti)
return 0; /* nothing is bound */
blocks = tc->pool->ti->len >> tc->pool->block_shift;
blocks = pool->ti->len;
(void) sector_div(blocks, pool->sectors_per_block);
if (blocks)
return fn(ti, tc->pool_dev, 0, tc->pool->sectors_per_block * blocks, data);
return fn(ti, tc->pool_dev, 0, pool->sectors_per_block * blocks, data);
return 0;
}
@ -2793,7 +2808,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
static struct target_type thin_target = {
.name = "thin",
.version = {1, 1, 0},
.version = {1, 2, 0},
.module = THIS_MODULE,
.ctr = thin_ctr,
.dtr = thin_dtr,