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* Copyright (C) 2003 Sistina Software (UK) Limited.
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* Copyright (C) 2004, 2010-2011 Red Hat, Inc. All rights reserved.
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* This file is released under the GPL.
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#include <linux/device-mapper.h>
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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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#define DM_MSG_PREFIX "flakey"
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#define all_corrupt_bio_flags_match(bio, fc) \
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(((bio)->bi_rw & (fc)->corrupt_bio_flags) == (fc)->corrupt_bio_flags)
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* Flakey: Used for testing only, simulates intermittent,
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* catastrophic device failure.
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unsigned long start_time;
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unsigned down_interval;
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unsigned corrupt_bio_byte;
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unsigned corrupt_bio_rw;
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unsigned corrupt_bio_value;
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unsigned corrupt_bio_flags;
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enum feature_flag_bits {
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static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
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static struct dm_arg _args[] = {
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{0, 6, "Invalid number of feature args"},
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{1, UINT_MAX, "Invalid corrupt bio byte"},
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{0, 255, "Invalid corrupt value to write into bio byte (0-255)"},
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{0, UINT_MAX, "Invalid corrupt bio flags mask"},
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/* No feature arguments supplied. */
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r = dm_read_arg_group(_args, as, &argc, &ti->error);
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arg_name = dm_shift_arg(as);
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if (!strcasecmp(arg_name, "drop_writes")) {
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if (test_and_set_bit(DROP_WRITES, &fc->flags)) {
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ti->error = "Feature drop_writes duplicated";
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* corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>
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if (!strcasecmp(arg_name, "corrupt_bio_byte")) {
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ti->error = "Feature corrupt_bio_byte requires parameters";
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r = dm_read_arg(_args + 1, as, &fc->corrupt_bio_byte, &ti->error);
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arg_name = dm_shift_arg(as);
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if (!strcasecmp(arg_name, "w"))
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fc->corrupt_bio_rw = WRITE;
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else if (!strcasecmp(arg_name, "r"))
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fc->corrupt_bio_rw = READ;
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ti->error = "Invalid corrupt bio direction (r or w)";
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* Value of byte (0-255) to write in place of correct one.
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r = dm_read_arg(_args + 2, as, &fc->corrupt_bio_value, &ti->error);
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* Only corrupt bios with these flags set.
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r = dm_read_arg(_args + 3, as, &fc->corrupt_bio_flags, &ti->error);
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ti->error = "Unrecognised flakey feature requested";
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if (test_bit(DROP_WRITES, &fc->flags) && (fc->corrupt_bio_rw == WRITE)) {
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ti->error = "drop_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
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* Construct a flakey mapping:
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* <dev_path> <offset> <up interval> <down interval> [<#feature args> [<arg>]*]
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* [corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>]
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* Nth_byte starts from 1 for the first byte.
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* Direction is r for READ or w for WRITE.
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* bio_flags is ignored if 0.
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static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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static struct dm_arg _args[] = {
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{0, UINT_MAX, "Invalid up interval"},
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{0, UINT_MAX, "Invalid down interval"},
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unsigned long long tmpll;
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struct dm_arg_set as;
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ti->error = "Invalid argument count";
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fc = kzalloc(sizeof(*fc), GFP_KERNEL);
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ti->error = "Cannot allocate linear context";
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fc->start_time = jiffies;
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devname = dm_shift_arg(&as);
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if (sscanf(dm_shift_arg(&as), "%llu", &tmpll) != 1) {
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ti->error = "Invalid device sector";
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r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
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r = dm_read_arg(_args, &as, &fc->down_interval, &ti->error);
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if (!(fc->up_interval + fc->down_interval)) {
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ti->error = "Total (up + down) interval is zero";
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if (fc->up_interval + fc->down_interval < fc->up_interval) {
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ti->error = "Interval overflow";
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r = parse_features(&as, fc, ti);
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if (dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev)) {
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ti->error = "Device lookup failed";
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ti->num_flush_requests = 1;
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ti->num_discard_requests = 1;
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static void flakey_dtr(struct dm_target *ti)
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struct flakey_c *fc = ti->private;
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dm_put_device(ti, fc->dev);
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static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
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struct flakey_c *fc = ti->private;
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return fc->start + dm_target_offset(ti, bi_sector);
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static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
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struct flakey_c *fc = ti->private;
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bio->bi_bdev = fc->dev->bdev;
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if (bio_sectors(bio))
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bio->bi_sector = flakey_map_sector(ti, bio->bi_sector);
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static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
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unsigned bio_bytes = bio_cur_bytes(bio);
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char *data = bio_data(bio);
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* Overwrite the Nth byte of the data returned.
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if (data && bio_bytes >= fc->corrupt_bio_byte) {
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data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
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DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
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"(rw=%c bi_rw=%lu bi_sector=%llu cur_bytes=%u)\n",
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bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
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(bio_data_dir(bio) == WRITE) ? 'w' : 'r',
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bio->bi_rw, (unsigned long long)bio->bi_sector, bio_bytes);
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static int flakey_map(struct dm_target *ti, struct bio *bio,
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union map_info *map_context)
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struct flakey_c *fc = ti->private;
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elapsed = (jiffies - fc->start_time) / HZ;
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if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
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* Flag this bio as submitted while down.
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* Map reads as normal.
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if (bio_data_dir(bio) == READ)
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if (test_bit(DROP_WRITES, &fc->flags)) {
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return DM_MAPIO_SUBMITTED;
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* Corrupt matching writes.
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if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
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if (all_corrupt_bio_flags_match(bio, fc))
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corrupt_bio_data(bio, fc);
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* By default, error all I/O.
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flakey_map_bio(ti, bio);
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return DM_MAPIO_REMAPPED;
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static int flakey_end_io(struct dm_target *ti, struct bio *bio,
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int error, union map_info *map_context)
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struct flakey_c *fc = ti->private;
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unsigned bio_submitted_while_down = map_context->ll;
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* Corrupt successful READs while in down state.
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* If flags were specified, only corrupt those that match.
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if (!error && bio_submitted_while_down &&
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(bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) &&
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all_corrupt_bio_flags_match(bio, fc))
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corrupt_bio_data(bio, fc);
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static int flakey_status(struct dm_target *ti, status_type_t type,
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char *result, unsigned int maxlen)
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struct flakey_c *fc = ti->private;
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unsigned drop_writes;
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case STATUSTYPE_INFO:
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case STATUSTYPE_TABLE:
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DMEMIT("%s %llu %u %u ", fc->dev->name,
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(unsigned long long)fc->start, fc->up_interval,
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drop_writes = test_bit(DROP_WRITES, &fc->flags);
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DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
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DMEMIT("drop_writes ");
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if (fc->corrupt_bio_byte)
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DMEMIT("corrupt_bio_byte %u %c %u %u ",
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fc->corrupt_bio_byte,
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(fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
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fc->corrupt_bio_value, fc->corrupt_bio_flags);
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static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
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struct flakey_c *fc = ti->private;
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return __blkdev_driver_ioctl(fc->dev->bdev, fc->dev->mode, cmd, arg);
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static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
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struct bio_vec *biovec, int max_size)
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struct flakey_c *fc = ti->private;
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struct request_queue *q = bdev_get_queue(fc->dev->bdev);
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if (!q->merge_bvec_fn)
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bvm->bi_bdev = fc->dev->bdev;
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bvm->bi_sector = flakey_map_sector(ti, bvm->bi_sector);
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return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
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static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
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struct flakey_c *fc = ti->private;
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return fn(ti, fc->dev, fc->start, ti->len, data);
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static struct target_type flakey_target = {
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.version = {1, 2, 0},
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.module = THIS_MODULE,
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.end_io = flakey_end_io,
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.status = flakey_status,
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.ioctl = flakey_ioctl,
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.merge = flakey_merge,
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.iterate_devices = flakey_iterate_devices,
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static int __init dm_flakey_init(void)
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int r = dm_register_target(&flakey_target);
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DMERR("register failed %d", r);
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static void __exit dm_flakey_exit(void)
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dm_unregister_target(&flakey_target);
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module_init(dm_flakey_init);
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module_exit(dm_flakey_exit);
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MODULE_DESCRIPTION(DM_NAME " flakey target");
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MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
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MODULE_LICENSE("GPL");