/* * Copyright (C) 2005-2007 Red Hat GmbH * * A target that delays reads and/or writes and can send * them to different devices. * * This file is released under the GPL. */ #include <linux/module.h> #include <linux/init.h> #include <linux/blkdev.h> #include <linux/bio.h> #include <linux/slab.h> #include <linux/device-mapper.h> #define DM_MSG_PREFIX "delay" struct delay_c { struct timer_list delay_timer; struct mutex timer_lock; struct work_struct flush_expired_bios; struct list_head delayed_bios; atomic_t may_delay; mempool_t *delayed_pool; struct dm_dev *dev_read; sector_t start_read; unsigned read_delay; unsigned reads; struct dm_dev *dev_write; sector_t start_write; unsigned write_delay; unsigned writes; }; struct dm_delay_info { struct delay_c *context; struct list_head list; struct bio *bio; unsigned long expires; }; static DEFINE_MUTEX(delayed_bios_lock); static struct workqueue_struct *kdelayd_wq; static struct kmem_cache *delayed_cache; static void handle_delayed_timer(unsigned long data) { struct delay_c *dc = (struct delay_c *)data; queue_work(kdelayd_wq, &dc->flush_expired_bios); } static void queue_timeout(struct delay_c *dc, unsigned long expires) { mutex_lock(&dc->timer_lock); if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires) mod_timer(&dc->delay_timer, expires); mutex_unlock(&dc->timer_lock); } static void flush_bios(struct bio *bio) { struct bio *n; while (bio) { n = bio->bi_next; bio->bi_next = NULL; generic_make_request(bio); bio = n; } } static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all) { struct dm_delay_info *delayed, *next; unsigned long next_expires = 0; int start_timer = 0; struct bio_list flush_bios = { }; mutex_lock(&delayed_bios_lock); list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) { if (flush_all || time_after_eq(jiffies, delayed->expires)) { list_del(&delayed->list); bio_list_add(&flush_bios, delayed->bio); if ((bio_data_dir(delayed->bio) == WRITE)) delayed->context->writes--; else delayed->context->reads--; mempool_free(delayed, dc->delayed_pool); continue; } if (!start_timer) { start_timer = 1; next_expires = delayed->expires; } else next_expires = min(next_expires, delayed->expires); } mutex_unlock(&delayed_bios_lock); if (start_timer) queue_timeout(dc, next_expires); return bio_list_get(&flush_bios); } static void flush_expired_bios(struct work_struct *work) { struct delay_c *dc; dc = container_of(work, struct delay_c, flush_expired_bios); flush_bios(flush_delayed_bios(dc, 0)); } /* * Mapping parameters: * <device> <offset> <delay> [<write_device> <write_offset> <write_delay>] * * With separate write parameters, the first set is only used for reads. * Delays are specified in milliseconds. */ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) { struct delay_c *dc; unsigned long long tmpll; if (argc != 3 && argc != 6) { ti->error = "requires exactly 3 or 6 arguments"; return -EINVAL; } dc = kmalloc(sizeof(*dc), GFP_KERNEL); if (!dc) { ti->error = "Cannot allocate context"; return -ENOMEM; } dc->reads = dc->writes = 0; if (sscanf(argv[1], "%llu", &tmpll) != 1) { ti->error = "Invalid device sector"; goto bad; } dc->start_read = tmpll; if (sscanf(argv[2], "%u", &dc->read_delay) != 1) { ti->error = "Invalid delay"; goto bad; } if (dm_get_device(ti, argv[0], dc->start_read, ti->len, dm_table_get_mode(ti->table), &dc->dev_read)) { ti->error = "Device lookup failed"; goto bad; } dc->dev_write = NULL; if (argc == 3) goto out; if (sscanf(argv[4], "%llu", &tmpll) != 1) { ti->error = "Invalid write device sector"; goto bad_dev_read; } dc->start_write = tmpll; if (sscanf(argv[5], "%u", &dc->write_delay) != 1) { ti->error = "Invalid write delay"; goto bad_dev_read; } if (dm_get_device(ti, argv[3], dc->start_write, ti->len, dm_table_get_mode(ti->table), &dc->dev_write)) { ti->error = "Write device lookup failed"; goto bad_dev_read; } out: dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache); if (!dc->delayed_pool) { DMERR("Couldn't create delayed bio pool."); goto bad_dev_write; } setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc); INIT_WORK(&dc->flush_expired_bios, flush_expired_bios); INIT_LIST_HEAD(&dc->delayed_bios); mutex_init(&dc->timer_lock); atomic_set(&dc->may_delay, 1); ti->num_flush_requests = 1; ti->private = dc; return 0; bad_dev_write: if (dc->dev_write) dm_put_device(ti, dc->dev_write); bad_dev_read: dm_put_device(ti, dc->dev_read); bad: kfree(dc); return -EINVAL; } static void delay_dtr(struct dm_target *ti) { struct delay_c *dc = ti->private; flush_workqueue(kdelayd_wq); dm_put_device(ti, dc->dev_read); if (dc->dev_write) dm_put_device(ti, dc->dev_write); mempool_destroy(dc->delayed_pool); kfree(dc); } static int delay_bio(struct delay_c *dc, int delay, struct bio *bio) { struct dm_delay_info *delayed; unsigned long expires = 0; if (!delay || !atomic_read(&dc->may_delay)) return 1; delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO); delayed->context = dc; delayed->bio = bio; delayed->expires = expires = jiffies + (delay * HZ / 1000); mutex_lock(&delayed_bios_lock); if (bio_data_dir(bio) == WRITE) dc->writes++; else dc->reads++; list_add_tail(&delayed->list, &dc->delayed_bios); mutex_unlock(&delayed_bios_lock); queue_timeout(dc, expires); return 0; } static void delay_presuspend(struct dm_target *ti) { struct delay_c *dc = ti->private; atomic_set(&dc->may_delay, 0); del_timer_sync(&dc->delay_timer); flush_bios(flush_delayed_bios(dc, 1)); } static void delay_resume(struct dm_target *ti) { struct delay_c *dc = ti->private; atomic_set(&dc->may_delay, 1); } static int delay_map(struct dm_target *ti, struct bio *bio, union map_info *map_context) { struct delay_c *dc = ti->private; if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) { bio->bi_bdev = dc->dev_write->bdev; if (bio_sectors(bio)) bio->bi_sector = dc->start_write + (bio->bi_sector - ti->begin); return delay_bio(dc, dc->write_delay, bio); } bio->bi_bdev = dc->dev_read->bdev; bio->bi_sector = dc->start_read + (bio->bi_sector - ti->begin); return delay_bio(dc, dc->read_delay, bio); } static int delay_status(struct dm_target *ti, status_type_t type, char *result, unsigned maxlen) { struct delay_c *dc = ti->private; int sz = 0; switch (type) { case STATUSTYPE_INFO: DMEMIT("%u %u", dc->reads, dc->writes); break; case STATUSTYPE_TABLE: DMEMIT("%s %llu %u", dc->dev_read->name, (unsigned long long) dc->start_read, dc->read_delay); if (dc->dev_write) DMEMIT(" %s %llu %u", dc->dev_write->name, (unsigned long long) dc->start_write, dc->write_delay); break; } return 0; } static int delay_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data) { struct delay_c *dc = ti->private; int ret = 0; ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data); if (ret) goto out; if (dc->dev_write) ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data); out: return ret; } static struct target_type delay_target = { .name = "delay", .version = {1, 1, 0}, .module = THIS_MODULE, .ctr = delay_ctr, .dtr = delay_dtr, .map = delay_map, .presuspend = delay_presuspend, .resume = delay_resume, .status = delay_status, .iterate_devices = delay_iterate_devices, }; static int __init dm_delay_init(void) { int r = -ENOMEM; kdelayd_wq = create_workqueue("kdelayd"); if (!kdelayd_wq) { DMERR("Couldn't start kdelayd"); goto bad_queue; } delayed_cache = KMEM_CACHE(dm_delay_info, 0); if (!delayed_cache) { DMERR("Couldn't create delayed bio cache."); goto bad_memcache; } r = dm_register_target(&delay_target); if (r < 0) { DMERR("register failed %d", r); goto bad_register; } return 0; bad_register: kmem_cache_destroy(delayed_cache); bad_memcache: destroy_workqueue(kdelayd_wq); bad_queue: return r; } static void __exit dm_delay_exit(void) { dm_unregister_target(&delay_target); kmem_cache_destroy(delayed_cache); destroy_workqueue(kdelayd_wq); } /* Module hooks */ module_init(dm_delay_init); module_exit(dm_delay_exit); MODULE_DESCRIPTION(DM_NAME " delay target"); MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>"); MODULE_LICENSE("GPL");