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dm: support non power of two target max_io_len

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Remove the restriction that limits a target's specified maximum incoming
I/O size to be a power of 2.

Rename this setting from 'split_io' to the less-ambiguous 'max_io_len'.
Change it from sector_t to uint32_t, which is plenty big enough, and
introduce a wrapper function dm_set_target_max_io_len() to set it.
Use sector_div() to process it now that it is not necessarily a power of 2.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mike Snitzer
2012-07-27 15:08:00 +01:00
committed by Alasdair G Kergon
parent 1df05483d7
commit 542f903814
8 changed files with 69 additions and 33 deletions
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27
drivers/md/dm-snap.c
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@@ -691,7 +691,7 @@ static int dm_add_exception(void *context, chunk_t old, chunk_t new)
* Return a minimum chunk size of all snapshots that have the specified origin.
* Return zero if the origin has no snapshots.
*/
static sector_t __minimum_chunk_size(struct origin *o)
static uint32_t __minimum_chunk_size(struct origin *o)
{
struct dm_snapshot *snap;
unsigned chunk_size = 0;
@@ -701,7 +701,7 @@ static sector_t __minimum_chunk_size(struct origin *o)
chunk_size = min_not_zero(chunk_size,
snap->store->chunk_size);
return chunk_size;
return (uint32_t) chunk_size;
}
/*
@@ -1172,7 +1172,10 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->error = "Chunk size not set";
goto bad_read_metadata;
}
ti->split_io = s->store->chunk_size;
r = dm_set_target_max_io_len(ti, s->store->chunk_size);
if (r)
goto bad_read_metadata;
return 0;
@@ -1239,7 +1242,7 @@ static void __handover_exceptions(struct dm_snapshot *snap_src,
snap_dest->store->snap = snap_dest;
snap_src->store->snap = snap_src;
snap_dest->ti->split_io = snap_dest->store->chunk_size;
snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
snap_dest->valid = snap_src->valid;
/*
@@ -1817,9 +1820,9 @@ static void snapshot_resume(struct dm_target *ti)
up_write(&s->lock);
}
static sector_t get_origin_minimum_chunksize(struct block_device *bdev)
static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
{
sector_t min_chunksize;
uint32_t min_chunksize;
down_read(&_origins_lock);
min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
@@ -1838,9 +1841,9 @@ static void snapshot_merge_resume(struct dm_target *ti)
snapshot_resume(ti);
/*
* snapshot-merge acts as an origin, so set ti->split_io
* snapshot-merge acts as an origin, so set ti->max_io_len
*/
ti->split_io = get_origin_minimum_chunksize(s->origin->bdev);
ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
start_merge(s);
}
@@ -2073,12 +2076,12 @@ static int origin_write_extent(struct dm_snapshot *merging_snap,
struct origin *o;
/*
* The origin's __minimum_chunk_size() got stored in split_io
* The origin's __minimum_chunk_size() got stored in max_io_len
* by snapshot_merge_resume().
*/
down_read(&_origins_lock);
o = __lookup_origin(merging_snap->origin->bdev);
for (n = 0; n < size; n += merging_snap->ti->split_io)
for (n = 0; n < size; n += merging_snap->ti->max_io_len)
if (__origin_write(&o->snapshots, sector + n, NULL) ==
DM_MAPIO_SUBMITTED)
must_wait = 1;
@@ -2138,14 +2141,14 @@ static int origin_map(struct dm_target *ti, struct bio *bio,
}
/*
* Set the target "split_io" field to the minimum of all the snapshots'
* Set the target "max_io_len" field to the minimum of all the snapshots'
* chunk sizes.
*/
static void origin_resume(struct dm_target *ti)
{
struct dm_dev *dev = ti->private;
ti->split_io = get_origin_minimum_chunksize(dev->bdev);
ti->max_io_len = get_origin_minimum_chunksize(dev->bdev);
}
static int origin_status(struct dm_target *ti, status_type_t type, char *result,