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dm cache: add data block size limits to code and Documentation 

Place upper bound on the cache's data block size (1GB).

Inform users that the data block size can't be any arbitrary number,
i.e. its value must be between 32KB and 1GB.  Also, it should be a
multiple of 32KB.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
This commit is contained in:
Mike Snitzer 2013-08-16 10:54:19 -04:00
parent 66bb2644ca
commit 0547304463
2 changed files with 12 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
Documentation/device-mapper/cache.txt
View File

@ -58,7 +58,8 @@ Fixed block size
The origin is divided up into blocks of a fixed size. This block size
is configurable when you first create the cache. Typically we've been
using block sizes of 256k - 1024k.
using block sizes of 256KB - 1024KB. The block size must be between 64
(32KB) and 2097152 (1GB) and a multiple of 64 (32KB).
Having a fixed block size simplifies the target a lot. But it is
something of a compromise. For instance, a small part of a block may be

17
drivers/md/dm-cache-target.c
View File

@ -67,9 +67,11 @@ static void free_bitset(unsigned long *bits)
#define MIGRATION_COUNT_WINDOW 10
/*
* The block size of the device holding cache data must be >= 32KB
* The block size of the device holding cache data must be
* between 32KB and 1GB.
*/
#define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (32 * 1024 >> SECTOR_SHIFT)
#define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)
/*
* FIXME: the cache is read/write for the time being.
@ -1687,24 +1689,25 @@ static int parse_origin_dev(struct cache_args *ca, struct dm_arg_set *as,
static int parse_block_size(struct cache_args *ca, struct dm_arg_set *as,
char **error)
{
unsigned long tmp;
unsigned long block_size;
if (!at_least_one_arg(as, error))
return -EINVAL;
if (kstrtoul(dm_shift_arg(as), 10, &tmp) || !tmp ||
tmp < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
tmp & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
if (kstrtoul(dm_shift_arg(as), 10, &block_size) || !block_size ||
block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS ||
block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
*error = "Invalid data block size";
return -EINVAL;
}
if (tmp > ca->cache_sectors) {
if (block_size > ca->cache_sectors) {
*error = "Data block size is larger than the cache device";
return -EINVAL;
}
ca->block_size = tmp;
ca->block_size = block_size;
return 0;
}