196 lines
3.2 KiB
C
196 lines
3.2 KiB
C
/*
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* Copyright (C) 2001 Sistina Software (UK) Limited
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*
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* This file is released under the GPL.
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*/
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#include "dm.h"
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/kmod.h>
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#include <linux/bio.h>
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#include <linux/slab.h>
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#define DM_MSG_PREFIX "target"
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struct tt_internal {
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struct target_type tt;
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struct list_head list;
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long use;
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};
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static LIST_HEAD(_targets);
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static DECLARE_RWSEM(_lock);
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#define DM_MOD_NAME_SIZE 32
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static inline struct tt_internal *__find_target_type(const char *name)
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{
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struct tt_internal *ti;
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list_for_each_entry (ti, &_targets, list)
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if (!strcmp(name, ti->tt.name))
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return ti;
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return NULL;
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}
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static struct tt_internal *get_target_type(const char *name)
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{
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struct tt_internal *ti;
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down_read(&_lock);
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ti = __find_target_type(name);
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if (ti) {
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if ((ti->use == 0) && !try_module_get(ti->tt.module))
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ti = NULL;
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else
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ti->use++;
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}
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up_read(&_lock);
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return ti;
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}
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static void load_module(const char *name)
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{
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request_module("dm-%s", name);
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}
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struct target_type *dm_get_target_type(const char *name)
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{
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struct tt_internal *ti = get_target_type(name);
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if (!ti) {
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load_module(name);
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ti = get_target_type(name);
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}
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return ti ? &ti->tt : NULL;
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}
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void dm_put_target_type(struct target_type *t)
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{
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struct tt_internal *ti = (struct tt_internal *) t;
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down_read(&_lock);
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if (--ti->use == 0)
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module_put(ti->tt.module);
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BUG_ON(ti->use < 0);
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up_read(&_lock);
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return;
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}
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static struct tt_internal *alloc_target(struct target_type *t)
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{
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struct tt_internal *ti = kzalloc(sizeof(*ti), GFP_KERNEL);
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if (ti)
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ti->tt = *t;
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return ti;
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}
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int dm_target_iterate(void (*iter_func)(struct target_type *tt,
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void *param), void *param)
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{
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struct tt_internal *ti;
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down_read(&_lock);
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list_for_each_entry (ti, &_targets, list)
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iter_func(&ti->tt, param);
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up_read(&_lock);
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return 0;
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}
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int dm_register_target(struct target_type *t)
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{
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int rv = 0;
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struct tt_internal *ti = alloc_target(t);
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if (!ti)
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return -ENOMEM;
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down_write(&_lock);
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if (__find_target_type(t->name))
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rv = -EEXIST;
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else
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list_add(&ti->list, &_targets);
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up_write(&_lock);
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if (rv)
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kfree(ti);
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return rv;
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}
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int dm_unregister_target(struct target_type *t)
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{
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struct tt_internal *ti;
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down_write(&_lock);
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if (!(ti = __find_target_type(t->name))) {
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up_write(&_lock);
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return -EINVAL;
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}
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if (ti->use) {
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up_write(&_lock);
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return -ETXTBSY;
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}
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list_del(&ti->list);
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kfree(ti);
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up_write(&_lock);
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return 0;
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}
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/*
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* io-err: always fails an io, useful for bringing
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* up LVs that have holes in them.
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*/
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static int io_err_ctr(struct dm_target *ti, unsigned int argc, char **args)
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{
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return 0;
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}
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static void io_err_dtr(struct dm_target *ti)
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{
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/* empty */
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}
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static int io_err_map(struct dm_target *ti, struct bio *bio,
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union map_info *map_context)
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{
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return -EIO;
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}
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static struct target_type error_target = {
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.name = "error",
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.version = {1, 0, 1},
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.ctr = io_err_ctr,
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.dtr = io_err_dtr,
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.map = io_err_map,
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};
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int __init dm_target_init(void)
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{
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return dm_register_target(&error_target);
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}
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void dm_target_exit(void)
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{
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if (dm_unregister_target(&error_target))
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DMWARN("error target unregistration failed");
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}
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EXPORT_SYMBOL(dm_register_target);
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EXPORT_SYMBOL(dm_unregister_target);
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