dm: add flakey target (3407ef52) · Commits · 戴 / test

Documentation/device-mapper/dm-flakey.txt

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		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.

drivers/md/Kconfig

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		@@ -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

drivers/md/Makefile

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		@@ -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

drivers/md/dm-flakey.c

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		/*
		* 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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