[Although I'm replying to this old email, I'm looking at
updated code taken from the all-caches branch of
git://github.com/jthornber/linux-2.6 ]
On Thu, Dec 13, 2012 at 08:19:16PM +0000, Joe Thornber wrote:
> drivers/md/Kconfig | 22 +
> drivers/md/dm-cache-policy-cleaner.c | 482 +++++
> drivers/md/dm-cache-policy-mq.c | 1254 +++++++++++++
> --- a/drivers/md/Kconfig
> +++ b/drivers/md/Kconfig
> +config DM_CACHE
> + tristate "Cache target (EXPERIMENTAL)"
> + depends on BLK_DEV_DM
> + default n
> + select DM_PERSISTENT_DATA
> + select DM_PRISON
> + ---help---
> + Use an SSD to speed up a slower device.
Can we allow for other non-SSD uses too?
"Use a faster device like an SSD to speed up a slower device." perhaps?
> + dm-cache attempts to improve performance of a block device by
> + moving frequently used data to a smaller, higher performance
> + device. Different 'policy' plugins can be used to change the
> + algorithms used to select which blocks are promoted, demoted,
> + cleaned etc. It supports writeback and writethrough modes.
> +++ b/drivers/md/dm-cache-policy-cleaner.c
> @@ -0,0 +1,482 @@
> +#include "dm-cache-policy.h"
> +#include "dm.h"
> +
> +#include <linux/hash.h>
> +#include <linux/list.h>
list.h already included by dm.h
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +
> +/*----------------------------------------------------------------*/
> +
#define DM_MSG_PREFIX "cache cleaner"
#define CLEANER_VERSION "1.0.0"
> +static int alloc_cache_blocks_with_hash(struct policy *p, dm_cblock_t cache_size)
> +{
> + int r;
int r = -ENOMEM ?
> +
> + p->cblocks = vzalloc(sizeof(*p->cblocks) * from_cblock(cache_size));
> + if (p->cblocks) {
> + unsigned u = from_cblock(cache_size);
> +
> + while (u--)
> + list_add(&p->cblocks[u].list, &p->free);
> +
> + p->nr_cblocks_allocated = 0;
> +
> + /* Cache entries hash. */
> + r = alloc_hash(&p->chash, from_cblock(cache_size));
> + if (r)
> + vfree(p->cblocks);
> +
> + } else
> + r = -ENOMEM;
Initialise instead.
> +}
> +
> +
> +static void __set_clear_dirty(struct dm_cache_policy *pe, dm_oblock_t oblock, bool set)
Extra blank line
> +#if 0
> +static int wb_status(struct dm_cache_policy *pe, status_type_t type, unsigned status_flags, char *result, unsigned maxlen)
> +{
> + ssize_t sz = 0;
> + struct policy *p = to_policy(pe);
> +
> + switch (type) {
> + case STATUSTYPE_INFO:
> + DMEMIT("%u", from_cblock(p->nr_dirty));
> + break;
> +
> + case STATUSTYPE_TABLE:
> + break;
> + }
> +
> + return 0;
> +}
> +#endif
Provide a documented stable status or drop this for now?
> +#if 0
> + p->policy.status = wb_status;
> + p->policy.message = NULL;
> +#endif
> +static int __init wb_init(void)
> +{
> + return dm_cache_policy_register(&wb_policy_type);
> +}
Log like other modules (e.g. dm-queue-length.c):
DMINFO("version " CLEANER_VERSION " loaded");
Similar DMINFO changes in dm-cache-policy-mq.c.
Alasdair
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