diff options
Diffstat (limited to 'drivers/md/dm-exception-store.c')
| -rw-r--r-- | drivers/md/dm-exception-store.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c index dccbfb0e010f..a2e26c242141 100644 --- a/drivers/md/dm-exception-store.c +++ b/drivers/md/dm-exception-store.c @@ -7,6 +7,7 @@ #include "dm-exception-store.h" +#include <linux/ctype.h> #include <linux/mm.h> #include <linux/pagemap.h> #include <linux/vmalloc.h> @@ -14,6 +15,257 @@ #define DM_MSG_PREFIX "snapshot exception stores" +static LIST_HEAD(_exception_store_types); +static DEFINE_SPINLOCK(_lock); + +static struct dm_exception_store_type *__find_exception_store_type(const char *name) +{ + struct dm_exception_store_type *type; + + list_for_each_entry(type, &_exception_store_types, list) + if (!strcmp(name, type->name)) + return type; + + return NULL; +} + +static struct dm_exception_store_type *_get_exception_store_type(const char *name) +{ + struct dm_exception_store_type *type; + + spin_lock(&_lock); + + type = __find_exception_store_type(name); + + if (type && !try_module_get(type->module)) + type = NULL; + + spin_unlock(&_lock); + + return type; +} + +/* + * get_type + * @type_name + * + * Attempt to retrieve the dm_exception_store_type by name. If not already + * available, attempt to load the appropriate module. + * + * Exstore modules are named "dm-exstore-" followed by the 'type_name'. + * Modules may contain multiple types. + * This function will first try the module "dm-exstore-<type_name>", + * then truncate 'type_name' on the last '-' and try again. + * + * For example, if type_name was "clustered-shared", it would search + * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'. + * + * 'dm-exception-store-<type_name>' is too long of a name in my + * opinion, which is why I've chosen to have the files + * containing exception store implementations be 'dm-exstore-<type_name>'. + * If you want your module to be autoloaded, you will follow this + * naming convention. + * + * Returns: dm_exception_store_type* on success, NULL on failure + */ +static struct dm_exception_store_type *get_type(const char *type_name) +{ + char *p, *type_name_dup; + struct dm_exception_store_type *type; + + type = _get_exception_store_type(type_name); + if (type) + return type; + + type_name_dup = kstrdup(type_name, GFP_KERNEL); + if (!type_name_dup) { + DMERR("No memory left to attempt load for \"%s\"", type_name); + return NULL; + } + + while (request_module("dm-exstore-%s", type_name_dup) || + !(type = _get_exception_store_type(type_name))) { + p = strrchr(type_name_dup, '-'); + if (!p) + break; + p[0] = '\0'; + } + + if (!type) + DMWARN("Module for exstore type \"%s\" not found.", type_name); + + kfree(type_name_dup); + + return type; +} + +static void put_type(struct dm_exception_store_type *type) +{ + spin_lock(&_lock); + module_put(type->module); + spin_unlock(&_lock); +} + +int dm_exception_store_type_register(struct dm_exception_store_type *type) +{ + int r = 0; + + spin_lock(&_lock); + if (!__find_exception_store_type(type->name)) + list_add(&type->list, &_exception_store_types); + else + r = -EEXIST; + spin_unlock(&_lock); + + return r; +} +EXPORT_SYMBOL(dm_exception_store_type_register); + +int dm_exception_store_type_unregister(struct dm_exception_store_type *type) +{ + spin_lock(&_lock); + + if (!__find_exception_store_type(type->name)) { + spin_unlock(&_lock); + return -EINVAL; + } + + list_del(&type->list); + + spin_unlock(&_lock); + + return 0; +} +EXPORT_SYMBOL(dm_exception_store_type_unregister); + +/* + * Round a number up to the nearest 'size' boundary. size must + * be a power of 2. + */ +static ulong round_up(ulong n, ulong size) +{ + size--; + return (n + size) & ~size; +} + +static int set_chunk_size(struct dm_exception_store *store, + const char *chunk_size_arg, char **error) +{ + unsigned long chunk_size_ulong; + char *value; + + chunk_size_ulong = simple_strtoul(chunk_size_arg, &value, 10); + if (*chunk_size_arg == '\0' || *value != '\0') { + *error = "Invalid chunk size"; + return -EINVAL; + } + + if (!chunk_size_ulong) { + store->chunk_size = store->chunk_mask = store->chunk_shift = 0; + return 0; + } + + /* + * Chunk size must be multiple of page size. Silently + * round up if it's not. + */ + chunk_size_ulong = round_up(chunk_size_ulong, PAGE_SIZE >> 9); + + /* Check chunk_size is a power of 2 */ + if (!is_power_of_2(chunk_size_ulong)) { + *error = "Chunk size is not a power of 2"; + return -EINVAL; + } + + /* Validate the chunk size against the device block size */ + if (chunk_size_ulong % (bdev_hardsect_size(store->cow->bdev) >> 9)) { + *error = "Chunk size is not a multiple of device blocksize"; + return -EINVAL; + } + + store->chunk_size = chunk_size_ulong; + store->chunk_mask = chunk_size_ulong - 1; + store->chunk_shift = ffs(chunk_size_ulong) - 1; + + return 0; +} + +int dm_exception_store_create(struct dm_target *ti, int argc, char **argv, + unsigned *args_used, + struct dm_exception_store **store) +{ + int r = 0; + struct dm_exception_store_type *type; + struct dm_exception_store *tmp_store; + char persistent; + + if (argc < 3) { + ti->error = "Insufficient exception store arguments"; + return -EINVAL; + } + + tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL); + if (!tmp_store) { + ti->error = "Exception store allocation failed"; + return -ENOMEM; + } + + persistent = toupper(*argv[1]); + if (persistent != 'P' && persistent != 'N') { + ti->error = "Persistent flag is not P or N"; + return -EINVAL; + } + + type = get_type(argv[1]); + if (!type) { + ti->error = "Exception store type not recognised"; + r = -EINVAL; + goto bad_type; + } + + tmp_store->type = type; + tmp_store->ti = ti; + + r = dm_get_device(ti, argv[0], 0, 0, + FMODE_READ | FMODE_WRITE, &tmp_store->cow); + if (r) { + ti->error = "Cannot get COW device"; + goto bad_cow; + } + + r = set_chunk_size(tmp_store, argv[2], &ti->error); + if (r) + goto bad_cow; + + r = type->ctr(tmp_store, 0, NULL); + if (r) { + ti->error = "Exception store type constructor failed"; + goto bad_ctr; + } + + *args_used = 3; + *store = tmp_store; + return 0; + +bad_ctr: + dm_put_device(ti, tmp_store->cow); +bad_cow: + put_type(type); +bad_type: + kfree(tmp_store); + return r; +} +EXPORT_SYMBOL(dm_exception_store_create); + +void dm_exception_store_destroy(struct dm_exception_store *store) +{ + store->type->dtr(store); + dm_put_device(store->ti, store->cow); + put_type(store->type); + kfree(store); +} +EXPORT_SYMBOL(dm_exception_store_destroy); + int dm_exception_store_init(void) { int r; |