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lvm2/driver/device-mapper/dm-target.c
Steven Whitehouse de37c802d7 o Targets now get rw passed through so they can do COW for example
o Added error handler (not sure that this is the "correct" way to do
   this at the moment, so its a bit exprimental for now)
2001-09-14 16:22:02 +00:00

159 lines
3.3 KiB
C

/*
* dm-target.c
*
* Copyright (C) 2001 Sistina Software
*
* This software is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU CC; see the file COPYING. If not, write to
* the Free Software Foundation, 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/*
* 16/08/2001 - First Version [Joe Thornber]
*/
#include "dm.h"
#include <linux/kmod.h>
static LIST_HEAD(dm_targets);
static rwlock_t dm_targets_lock = RW_LOCK_UNLOCKED;
#define DM_MOD_NAME_SIZE 32
struct target_type *dm_get_target_type(const char *name)
{
struct list_head *tmp, *head;
struct target_type *t;
int try = 0;
/* Length check for strcat() below */
if (strlen(name) > (DM_MOD_NAME_SIZE - 4))
return NULL;
try_again:
read_lock(&dm_targets_lock);
tmp = head = &dm_targets;
for(;;) {
tmp = tmp->next;
if (tmp == head)
break;
t = list_entry(tmp, struct target_type, list);
if (strcmp(name, t->name) == 0) {
if (t->use == 0 && t->module)
__MOD_INC_USE_COUNT(t->module);
t->use++;
read_unlock(&dm_targets_lock);
return t;
}
}
read_unlock(&dm_targets_lock);
if (try++ == 0) {
char module_name[DM_MOD_NAME_SIZE] = "dm-";
/* strcat() is only safe due to length check above */
strcat(module_name, name);
request_module(module_name);
goto try_again;
}
return NULL;
}
void dm_put_target_type(struct target_type *t)
{
read_lock(&dm_targets_lock);
if (--t->use == 0 && t->module)
__MOD_DEC_USE_COUNT(t->module);
if (t->use < 0)
BUG();
read_unlock(&dm_targets_lock);
}
int dm_register_target(struct target_type *t)
{
struct list_head *tmp, *head;
struct target_type *t2;
int rv = 0;
write_lock(&dm_targets_lock);
tmp = head = &dm_targets;
for(;;) {
if (tmp == head)
break;
t2 = list_entry(tmp, struct target_type, list);
if (strcmp(t->name, t2->name) != 0)
continue;
rv = -EEXIST;
break;
}
if (rv == 0)
list_add(&t->list, &dm_targets);
write_unlock(&dm_targets_lock);
return rv;
}
int dm_unregister_target(struct target_type *t)
{
int rv = -ETXTBSY;
write_lock(&dm_targets_lock);
if (t->use == 0) {
list_del(&t->list);
rv = 0;
}
write_unlock(&dm_targets_lock);
return rv;
}
/*
* io-err: always fails an io, useful for bringing
* up LV's that have holes in them.
*/
static int io_err_ctr(struct dm_table *t, offset_t b, offset_t l,
struct text_region *args, void **result,
dm_error_fn fn, void *private)
{
/* this takes no arguments */
*result = 0;
return 0;
}
static void io_err_dtr(struct dm_table *t, void *c)
{
/* empty */
}
static int io_err_map(struct buffer_head *bh, int rw, void *context)
{
buffer_IO_error(bh);
return 0;
}
static struct target_type error_target = {
name: "error",
ctr: io_err_ctr,
dtr: io_err_dtr,
map: io_err_map
};
int dm_target_init(void)
{
return dm_register_target(&error_target);
}
EXPORT_SYMBOL(dm_register_target);
EXPORT_SYMBOL(dm_unregister_target);