dm: delay target
New device-mapper target that can delay I/O (for testing). Reads can be separated from writes, redirected to different underlying devices and delayed by differing amounts of time. Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com> Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Heinz Mauelshagen
Linus Torvalds
Родитель
0ba699347e
Коммит
26b9f22870
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@ -0,0 +1,26 @@
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dm-delay
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========
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Device-Mapper's "delay" target delays reads and/or writes
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and maps them to different devices.
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Parameters:
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<device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
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With separate write parameters, the first set is only used for reads.
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Delays are specified in milliseconds.
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Example scripts
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===============
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[[
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#!/bin/sh
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# Create device delaying rw operation for 500ms
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echo "0 `blockdev --getsize $1` delay $1 0 500" | dmsetup create delayed
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]]
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[[
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#!/bin/sh
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# Create device delaying only write operation for 500ms and
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# splitting reads and writes to different devices $1 $2
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echo "0 `blockdev --getsize $1` delay $1 0 0 $2 0 500" | dmsetup create delayed
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]]
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@ -262,6 +262,15 @@ config DM_MULTIPATH_EMC
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---help---
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Multipath support for EMC CX/AX series hardware.
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config DM_DELAY
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tristate "I/O delaying target (EXPERIMENTAL)"
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depends on BLK_DEV_DM && EXPERIMENTAL
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---help---
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A target that delays reads and/or writes and can send
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them to different devices. Useful for testing.
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If unsure, say N.
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endmenu
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endif
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@ -31,6 +31,7 @@ obj-$(CONFIG_MD_FAULTY) += faulty.o
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obj-$(CONFIG_BLK_DEV_MD) += md-mod.o
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obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o
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obj-$(CONFIG_DM_CRYPT) += dm-crypt.o
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obj-$(CONFIG_DM_DELAY) += dm-delay.o
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obj-$(CONFIG_DM_MULTIPATH) += dm-multipath.o dm-round-robin.o
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obj-$(CONFIG_DM_MULTIPATH_EMC) += dm-emc.o
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obj-$(CONFIG_DM_SNAPSHOT) += dm-snapshot.o
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@ -0,0 +1,383 @@
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/*
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* Copyright (C) 2005-2007 Red Hat GmbH
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*
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* A target that delays reads and/or writes and can send
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* them to different devices.
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*
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* This file is released under the GPL.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/blkdev.h>
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#include <linux/bio.h>
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#include <linux/slab.h>
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#include "dm.h"
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#include "dm-bio-list.h"
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#define DM_MSG_PREFIX "delay"
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struct delay_c {
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struct timer_list delay_timer;
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struct semaphore timer_lock;
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struct work_struct flush_expired_bios;
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struct list_head delayed_bios;
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atomic_t may_delay;
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mempool_t *delayed_pool;
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struct dm_dev *dev_read;
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sector_t start_read;
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unsigned read_delay;
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unsigned reads;
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struct dm_dev *dev_write;
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sector_t start_write;
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unsigned write_delay;
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unsigned writes;
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};
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struct delay_info {
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struct delay_c *context;
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struct list_head list;
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struct bio *bio;
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unsigned long expires;
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};
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static DEFINE_MUTEX(delayed_bios_lock);
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static struct workqueue_struct *kdelayd_wq;
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static struct kmem_cache *delayed_cache;
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static void handle_delayed_timer(unsigned long data)
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{
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struct delay_c *dc = (struct delay_c *)data;
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queue_work(kdelayd_wq, &dc->flush_expired_bios);
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}
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static void queue_timeout(struct delay_c *dc, unsigned long expires)
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{
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down(&dc->timer_lock);
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if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
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mod_timer(&dc->delay_timer, expires);
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up(&dc->timer_lock);
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}
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static void flush_bios(struct bio *bio)
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{
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struct bio *n;
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while (bio) {
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n = bio->bi_next;
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bio->bi_next = NULL;
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generic_make_request(bio);
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bio = n;
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}
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}
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static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all)
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{
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struct delay_info *delayed, *next;
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unsigned long next_expires = 0;
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int start_timer = 0;
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BIO_LIST(flush_bios);
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mutex_lock(&delayed_bios_lock);
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list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
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if (flush_all || time_after_eq(jiffies, delayed->expires)) {
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list_del(&delayed->list);
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bio_list_add(&flush_bios, delayed->bio);
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if ((bio_data_dir(delayed->bio) == WRITE))
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delayed->context->writes--;
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else
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delayed->context->reads--;
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mempool_free(delayed, dc->delayed_pool);
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continue;
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}
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if (!start_timer) {
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start_timer = 1;
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next_expires = delayed->expires;
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} else
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next_expires = min(next_expires, delayed->expires);
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}
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mutex_unlock(&delayed_bios_lock);
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if (start_timer)
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queue_timeout(dc, next_expires);
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return bio_list_get(&flush_bios);
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}
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static void flush_expired_bios(struct work_struct *work)
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{
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struct delay_c *dc;
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dc = container_of(work, struct delay_c, flush_expired_bios);
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flush_bios(flush_delayed_bios(dc, 0));
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}
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/*
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* Mapping parameters:
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* <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
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*
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* With separate write parameters, the first set is only used for reads.
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* Delays are specified in milliseconds.
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*/
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static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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{
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struct delay_c *dc;
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unsigned long long tmpll;
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if (argc != 3 && argc != 6) {
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ti->error = "requires exactly 3 or 6 arguments";
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return -EINVAL;
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}
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dc = kmalloc(sizeof(*dc), GFP_KERNEL);
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if (!dc) {
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ti->error = "Cannot allocate context";
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return -ENOMEM;
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}
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dc->reads = dc->writes = 0;
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if (sscanf(argv[1], "%llu", &tmpll) != 1) {
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ti->error = "Invalid device sector";
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goto bad;
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}
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dc->start_read = tmpll;
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if (sscanf(argv[2], "%u", &dc->read_delay) != 1) {
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ti->error = "Invalid delay";
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goto bad;
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}
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if (dm_get_device(ti, argv[0], dc->start_read, ti->len,
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dm_table_get_mode(ti->table), &dc->dev_read)) {
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ti->error = "Device lookup failed";
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goto bad;
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}
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if (argc == 3) {
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dc->dev_write = NULL;
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goto out;
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}
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if (sscanf(argv[4], "%llu", &tmpll) != 1) {
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ti->error = "Invalid write device sector";
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goto bad;
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}
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dc->start_write = tmpll;
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if (sscanf(argv[5], "%u", &dc->write_delay) != 1) {
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ti->error = "Invalid write delay";
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goto bad;
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}
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if (dm_get_device(ti, argv[3], dc->start_write, ti->len,
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dm_table_get_mode(ti->table), &dc->dev_write)) {
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ti->error = "Write device lookup failed";
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dm_put_device(ti, dc->dev_read);
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goto bad;
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}
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out:
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dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache);
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if (!dc->delayed_pool) {
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DMERR("Couldn't create delayed bio pool.");
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goto bad;
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}
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init_timer(&dc->delay_timer);
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dc->delay_timer.function = handle_delayed_timer;
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dc->delay_timer.data = (unsigned long)dc;
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INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
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INIT_LIST_HEAD(&dc->delayed_bios);
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init_MUTEX(&dc->timer_lock);
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atomic_set(&dc->may_delay, 1);
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ti->private = dc;
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return 0;
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bad:
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kfree(dc);
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return -EINVAL;
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}
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static void delay_dtr(struct dm_target *ti)
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{
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struct delay_c *dc = ti->private;
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flush_workqueue(kdelayd_wq);
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dm_put_device(ti, dc->dev_read);
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if (dc->dev_write)
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dm_put_device(ti, dc->dev_write);
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mempool_destroy(dc->delayed_pool);
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kfree(dc);
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}
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static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
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{
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struct delay_info *delayed;
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unsigned long expires = 0;
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if (!delay || !atomic_read(&dc->may_delay))
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return 1;
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delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
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delayed->context = dc;
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delayed->bio = bio;
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delayed->expires = expires = jiffies + (delay * HZ / 1000);
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mutex_lock(&delayed_bios_lock);
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if (bio_data_dir(bio) == WRITE)
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dc->writes++;
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else
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dc->reads++;
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list_add_tail(&delayed->list, &dc->delayed_bios);
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mutex_unlock(&delayed_bios_lock);
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queue_timeout(dc, expires);
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return 0;
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}
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static void delay_presuspend(struct dm_target *ti)
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{
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struct delay_c *dc = ti->private;
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atomic_set(&dc->may_delay, 0);
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del_timer_sync(&dc->delay_timer);
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flush_bios(flush_delayed_bios(dc, 1));
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}
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static void delay_resume(struct dm_target *ti)
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{
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struct delay_c *dc = ti->private;
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atomic_set(&dc->may_delay, 1);
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}
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static int delay_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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struct delay_c *dc = ti->private;
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if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
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bio->bi_bdev = dc->dev_write->bdev;
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bio->bi_sector = dc->start_write +
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(bio->bi_sector - ti->begin);
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return delay_bio(dc, dc->write_delay, bio);
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}
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bio->bi_bdev = dc->dev_read->bdev;
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bio->bi_sector = dc->start_read +
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(bio->bi_sector - ti->begin);
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return delay_bio(dc, dc->read_delay, bio);
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}
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static int delay_status(struct dm_target *ti, status_type_t type,
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char *result, unsigned maxlen)
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{
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struct delay_c *dc = ti->private;
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int sz = 0;
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switch (type) {
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case STATUSTYPE_INFO:
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DMEMIT("%u %u", dc->reads, dc->writes);
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break;
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case STATUSTYPE_TABLE:
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DMEMIT("%s %llu %u", dc->dev_read->name,
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(unsigned long long) dc->start_read,
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dc->read_delay);
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if (dc->dev_write)
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DMEMIT("%s %llu %u", dc->dev_write->name,
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(unsigned long long) dc->start_write,
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dc->write_delay);
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break;
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}
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return 0;
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}
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static struct target_type delay_target = {
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.name = "delay",
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.version = {1, 0, 2},
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.module = THIS_MODULE,
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.ctr = delay_ctr,
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.dtr = delay_dtr,
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.map = delay_map,
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.presuspend = delay_presuspend,
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.resume = delay_resume,
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.status = delay_status,
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};
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static int __init dm_delay_init(void)
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{
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int r = -ENOMEM;
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kdelayd_wq = create_workqueue("kdelayd");
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if (!kdelayd_wq) {
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DMERR("Couldn't start kdelayd");
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goto bad_queue;
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}
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delayed_cache = kmem_cache_create("dm-delay",
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sizeof(struct delay_info),
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__alignof__(struct delay_info),
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0, NULL, NULL);
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if (!delayed_cache) {
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DMERR("Couldn't create delayed bio cache.");
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goto bad_memcache;
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}
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r = dm_register_target(&delay_target);
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if (r < 0) {
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DMERR("register failed %d", r);
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goto bad_register;
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}
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return 0;
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bad_register:
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kmem_cache_destroy(delayed_cache);
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bad_memcache:
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destroy_workqueue(kdelayd_wq);
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bad_queue:
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return r;
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}
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static void __exit dm_delay_exit(void)
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{
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int r = dm_unregister_target(&delay_target);
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if (r < 0)
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DMERR("unregister failed %d", r);
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kmem_cache_destroy(delayed_cache);
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destroy_workqueue(kdelayd_wq);
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}
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/* Module hooks */
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module_init(dm_delay_init);
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module_exit(dm_delay_exit);
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MODULE_DESCRIPTION(DM_NAME " delay target");
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MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
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MODULE_LICENSE("GPL");
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