Commit 3407ef52 authored by Josef Bacik's avatar Josef Bacik Committed by Alasdair G Kergon

dm: add flakey target

This target is the same as the linear target except that it returns I/O
errors periodically.  It's been found useful in simulating failing
devices for testing purposes.

I needed a dm target to do some failure testing on btrfs's raid code, and
Mike pointed me at this.
Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 024d37e9
dm-flakey
=========
This target is the same as the linear target except that it returns I/O
errors periodically. It's been found useful in simulating failing
devices for testing purposes.
Starting from the time the table is loaded, the device is available for
<up interval> seconds, then returns errors for <down interval> seconds,
and then this cycle repeats.
Parameters: <dev path> <offset> <up interval> <down interval>
<dev path>: Full pathname to the underlying block-device, or a
"major:minor" device-number.
<offset>: Starting sector within the device.
<up interval>: Number of seconds device is available.
<down interval>: Number of seconds device returns errors.
......@@ -327,4 +327,10 @@ config DM_UEVENT
---help---
Generate udev events for DM events.
config DM_FLAKEY
tristate "Flakey target (EXPERIMENTAL)"
depends on BLK_DEV_DM && EXPERIMENTAL
---help---
A target that intermittently fails I/O for debugging purposes.
endif # MD
......@@ -29,6 +29,7 @@ obj-$(CONFIG_BLK_DEV_MD) += md-mod.o
obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o
obj-$(CONFIG_DM_CRYPT) += dm-crypt.o
obj-$(CONFIG_DM_DELAY) += dm-delay.o
obj-$(CONFIG_DM_FLAKEY) += dm-flakey.o
obj-$(CONFIG_DM_MULTIPATH) += dm-multipath.o dm-round-robin.o
obj-$(CONFIG_DM_MULTIPATH_QL) += dm-queue-length.o
obj-$(CONFIG_DM_MULTIPATH_ST) += dm-service-time.o
......
/*
* Copyright (C) 2003 Sistina Software (UK) Limited.
* Copyright (C) 2004, 2010 Red Hat, Inc. All rights reserved.
*
* This file is released under the GPL.
*/
#include <linux/device-mapper.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/slab.h>
#define DM_MSG_PREFIX "flakey"
/*
* Flakey: Used for testing only, simulates intermittent,
* catastrophic device failure.
*/
struct flakey_c {
struct dm_dev *dev;
unsigned long start_time;
sector_t start;
unsigned up_interval;
unsigned down_interval;
};
/*
* Construct a flakey mapping: <dev_path> <offset> <up interval> <down interval>
*/
static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct flakey_c *fc;
unsigned long long tmp;
if (argc != 4) {
ti->error = "dm-flakey: Invalid argument count";
return -EINVAL;
}
fc = kmalloc(sizeof(*fc), GFP_KERNEL);
if (!fc) {
ti->error = "dm-flakey: Cannot allocate linear context";
return -ENOMEM;
}
fc->start_time = jiffies;
if (sscanf(argv[1], "%llu", &tmp) != 1) {
ti->error = "dm-flakey: Invalid device sector";
goto bad;
}
fc->start = tmp;
if (sscanf(argv[2], "%u", &fc->up_interval) != 1) {
ti->error = "dm-flakey: Invalid up interval";
goto bad;
}
if (sscanf(argv[3], "%u", &fc->down_interval) != 1) {
ti->error = "dm-flakey: Invalid down interval";
goto bad;
}
if (!(fc->up_interval + fc->down_interval)) {
ti->error = "dm-flakey: Total (up + down) interval is zero";
goto bad;
}
if (fc->up_interval + fc->down_interval < fc->up_interval) {
ti->error = "dm-flakey: Interval overflow";
goto bad;
}
if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &fc->dev)) {
ti->error = "dm-flakey: Device lookup failed";
goto bad;
}
ti->num_flush_requests = 1;
ti->private = fc;
return 0;
bad:
kfree(fc);
return -EINVAL;
}
static void flakey_dtr(struct dm_target *ti)
{
struct flakey_c *fc = ti->private;
dm_put_device(ti, fc->dev);
kfree(fc);
}
static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
{
struct flakey_c *fc = ti->private;
return fc->start + (bi_sector - ti->begin);
}
static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
{
struct flakey_c *fc = ti->private;
bio->bi_bdev = fc->dev->bdev;
if (bio_sectors(bio))
bio->bi_sector = flakey_map_sector(ti, bio->bi_sector);
}
static int flakey_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct flakey_c *fc = ti->private;
unsigned elapsed;
/* Are we alive ? */
elapsed = (jiffies - fc->start_time) / HZ;
if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval)
return -EIO;
flakey_map_bio(ti, bio);
return DM_MAPIO_REMAPPED;
}
static int flakey_status(struct dm_target *ti, status_type_t type,
char *result, unsigned int maxlen)
{
struct flakey_c *fc = ti->private;
switch (type) {
case STATUSTYPE_INFO:
result[0] = '\0';
break;
case STATUSTYPE_TABLE:
snprintf(result, maxlen, "%s %llu %u %u", fc->dev->name,
(unsigned long long)fc->start, fc->up_interval,
fc->down_interval);
break;
}
return 0;
}
static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
{
struct flakey_c *fc = ti->private;
return __blkdev_driver_ioctl(fc->dev->bdev, fc->dev->mode, cmd, arg);
}
static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
struct bio_vec *biovec, int max_size)
{
struct flakey_c *fc = ti->private;
struct request_queue *q = bdev_get_queue(fc->dev->bdev);
if (!q->merge_bvec_fn)
return max_size;
bvm->bi_bdev = fc->dev->bdev;
bvm->bi_sector = flakey_map_sector(ti, bvm->bi_sector);
return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}
static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
{
struct flakey_c *fc = ti->private;
return fn(ti, fc->dev, fc->start, ti->len, data);
}
static struct target_type flakey_target = {
.name = "flakey",
.version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = flakey_ctr,
.dtr = flakey_dtr,
.map = flakey_map,
.status = flakey_status,
.ioctl = flakey_ioctl,
.merge = flakey_merge,
.iterate_devices = flakey_iterate_devices,
};
static int __init dm_flakey_init(void)
{
int r = dm_register_target(&flakey_target);
if (r < 0)
DMERR("register failed %d", r);
return r;
}
static void __exit dm_flakey_exit(void)
{
dm_unregister_target(&flakey_target);
}
/* Module hooks */
module_init(dm_flakey_init);
module_exit(dm_flakey_exit);
MODULE_DESCRIPTION(DM_NAME " flakey target");
MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");
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