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dm thin: generate event when metadata threshold passed

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Generate a dm event when the amount of remaining thin pool metadata
space falls below a certain level.

The threshold is taken to be a quarter of the size of the metadata
device with a minimum threshold of 4MB.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Joe Thornber 2013-05-10 14:37:21 +01:00 committed by Alasdair G Kergon
parent 2fc48021f4
commit ac8c3f3df6
3 changed files with 58 additions and 0 deletions
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14
drivers/md/dm-thin-metadata.c
View File

@ -1696,3 +1696,17 @@ void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd)
dm_bm_set_read_only(pmd->bm);
up_write(&pmd->root_lock);
}
int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
dm_block_t threshold,
dm_sm_threshold_fn fn,
void *context)
{
int r;
down_write(&pmd->root_lock);
r = dm_sm_register_threshold_callback(pmd->metadata_sm, threshold, fn, context);
up_write(&pmd->root_lock);
return r;
}

6
drivers/md/dm-thin-metadata.h
View File

@ -8,6 +8,7 @@
#define DM_THIN_METADATA_H
#include "persistent-data/dm-block-manager.h"
#include "persistent-data/dm-space-map.h"
#define THIN_METADATA_BLOCK_SIZE 4096
@ -193,6 +194,11 @@ int dm_pool_resize_metadata_dev(struct dm_pool_metadata *pmd, dm_block_t new_siz
*/
void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd);
int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
dm_block_t threshold,
dm_sm_threshold_fn fn,
void *context);
/*----------------------------------------------------------------*/
#endif

38
drivers/md/dm-thin.c
View File

@ -1281,6 +1281,10 @@ static void process_bio_fail(struct thin_c *tc, struct bio *bio)
bio_io_error(bio);
}
/*
* FIXME: should we also commit due to size of transaction, measured in
* metadata blocks?
*/
static int need_commit_due_to_time(struct pool *pool)
{
return jiffies < pool->last_commit_jiffies ||
@ -1909,6 +1913,16 @@ static int parse_pool_features(struct dm_arg_set *as, struct pool_features *pf,
return r;
}
static void metadata_low_callback(void *context)
{
struct pool *pool = context;
DMWARN("%s: reached low water mark for metadata device: sending event.",
dm_device_name(pool->pool_md));
dm_table_event(pool->ti->table);
}
static sector_t get_metadata_dev_size(struct block_device *bdev)
{
sector_t metadata_dev_size = i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
@ -1932,6 +1946,23 @@ static dm_block_t get_metadata_dev_size_in_blocks(struct block_device *bdev)
return metadata_dev_size;
}
/*
* When a metadata threshold is crossed a dm event is triggered, and
* userland should respond by growing the metadata device. We could let
* userland set the threshold, like we do with the data threshold, but I'm
* not sure they know enough to do this well.
*/
static dm_block_t calc_metadata_threshold(struct pool_c *pt)
{
/*
* 4M is ample for all ops with the possible exception of thin
* device deletion which is harmless if it fails (just retry the
* delete after you've grown the device).
*/
dm_block_t quarter = get_metadata_dev_size_in_blocks(pt->metadata_dev->bdev) / 4;
return min((dm_block_t)1024ULL /* 4M */, quarter);
}
/*
* thin-pool <metadata dev> <data dev>
* <data block size (sectors)>
@ -2065,6 +2096,13 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
}
ti->private = pt;
r = dm_pool_register_metadata_threshold(pt->pool->pmd,
calc_metadata_threshold(pt),
metadata_low_callback,
pool);
if (r)
goto out_free_pt;
pt->callbacks.congested_fn = pool_is_congested;
dm_table_add_target_callbacks(ti->table, &pt->callbacks);