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f083b09b78
The DM_TARGET_WILDCARD feature indicates that the "error" target may replace any target; even immutable targets. This feature will be useful to preserve the ability to replace the "multipath" target even once it is formally converted over to having the DM_TARGET_IMMUTABLE feature. Also, implicit in the DM_TARGET_WILDCARD feature flag being set is that .map, .map_rq, .clone_and_map_rq and .release_clone_rq are all defined in the target_type. Signed-off-by: Mike Snitzer <snitzer@redhat.com>
175 lines
3.1 KiB
C
175 lines
3.1 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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#define DM_MSG_PREFIX "target"
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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 target_type *__find_target_type(const char *name)
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{
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struct target_type *tt;
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list_for_each_entry(tt, &_targets, list)
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if (!strcmp(name, tt->name))
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return tt;
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return NULL;
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}
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static struct target_type *get_target_type(const char *name)
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{
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struct target_type *tt;
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down_read(&_lock);
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tt = __find_target_type(name);
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if (tt && !try_module_get(tt->module))
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tt = NULL;
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up_read(&_lock);
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return tt;
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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 target_type *tt = get_target_type(name);
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if (!tt) {
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load_module(name);
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tt = get_target_type(name);
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}
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return tt;
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}
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void dm_put_target_type(struct target_type *tt)
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{
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down_read(&_lock);
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module_put(tt->module);
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up_read(&_lock);
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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 target_type *tt;
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down_read(&_lock);
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list_for_each_entry(tt, &_targets, list)
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iter_func(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 *tt)
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{
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int rv = 0;
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down_write(&_lock);
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if (__find_target_type(tt->name))
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rv = -EEXIST;
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else
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list_add(&tt->list, &_targets);
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up_write(&_lock);
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return rv;
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}
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void dm_unregister_target(struct target_type *tt)
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{
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down_write(&_lock);
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if (!__find_target_type(tt->name)) {
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DMCRIT("Unregistering unrecognised target: %s", tt->name);
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BUG();
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}
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list_del(&tt->list);
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up_write(&_lock);
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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 *tt, unsigned int argc, char **args)
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{
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/*
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* Return error for discards instead of -EOPNOTSUPP
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*/
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tt->num_discard_bios = 1;
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return 0;
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}
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static void io_err_dtr(struct dm_target *tt)
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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 *tt, struct bio *bio)
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{
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return -EIO;
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}
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static int io_err_map_rq(struct dm_target *ti, struct request *clone,
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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 int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
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union map_info *map_context,
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struct request **clone)
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{
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return -EIO;
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}
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static void io_err_release_clone_rq(struct request *clone)
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{
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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, 4, 0},
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.features = DM_TARGET_WILDCARD,
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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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.map_rq = io_err_map_rq,
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.clone_and_map_rq = io_err_clone_and_map_rq,
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.release_clone_rq = io_err_release_clone_rq,
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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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dm_unregister_target(&error_target);
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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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