b26f5e3d71
Add 'drop_writes' option to drop writes silently while the device is 'down'. Reads are not touched. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
305 lines
6.1 KiB
C
305 lines
6.1 KiB
C
/*
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* Copyright (C) 2003 Sistina Software (UK) Limited.
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* Copyright (C) 2004, 2010 Red Hat, Inc. All rights reserved.
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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/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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/*
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* Flakey: Used for testing only, simulates intermittent,
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* catastrophic device failure.
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*/
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struct flakey_c {
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struct dm_dev *dev;
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unsigned long start_time;
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sector_t start;
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unsigned up_interval;
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unsigned down_interval;
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unsigned long flags;
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};
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enum feature_flag_bits {
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DROP_WRITES
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};
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static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
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struct dm_target *ti)
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{
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int r;
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unsigned argc;
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const char *arg_name;
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static struct dm_arg _args[] = {
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{0, 1, "Invalid number of feature args"},
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};
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/* No feature arguments supplied. */
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if (!as->argc)
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return 0;
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r = dm_read_arg_group(_args, as, &argc, &ti->error);
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if (r)
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return -EINVAL;
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while (argc && !r) {
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arg_name = dm_shift_arg(as);
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argc--;
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/*
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* drop_writes
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*/
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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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return -EINVAL;
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}
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continue;
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}
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ti->error = "Unrecognised flakey feature requested";
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r = -EINVAL;
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}
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return r;
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}
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/*
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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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*
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* Feature args:
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* [drop_writes]
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*/
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static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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{
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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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};
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int r;
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struct flakey_c *fc;
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unsigned long long tmpll;
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struct dm_arg_set as;
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const char *devname;
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as.argc = argc;
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as.argv = argv;
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if (argc < 4) {
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ti->error = "Invalid argument count";
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return -EINVAL;
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}
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fc = kzalloc(sizeof(*fc), GFP_KERNEL);
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if (!fc) {
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ti->error = "Cannot allocate linear context";
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return -ENOMEM;
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}
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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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goto bad;
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}
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fc->start = tmpll;
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r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
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if (r)
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goto bad;
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r = dm_read_arg(_args, &as, &fc->down_interval, &ti->error);
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if (r)
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goto bad;
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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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goto bad;
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}
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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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goto bad;
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}
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r = parse_features(&as, fc, ti);
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if (r)
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goto bad;
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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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goto bad;
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}
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ti->num_flush_requests = 1;
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ti->num_discard_requests = 1;
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ti->private = fc;
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return 0;
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bad:
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kfree(fc);
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return -EINVAL;
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}
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static void flakey_dtr(struct dm_target *ti)
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{
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struct flakey_c *fc = ti->private;
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dm_put_device(ti, fc->dev);
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kfree(fc);
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}
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static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
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{
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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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}
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static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
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{
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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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}
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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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{
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struct flakey_c *fc = ti->private;
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unsigned elapsed;
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unsigned rw;
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/* Are we alive ? */
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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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rw = bio_data_dir(bio);
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/*
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* Drop writes. Map reads as normal.
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*/
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if (test_bit(DROP_WRITES, &fc->flags)) {
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if (rw == WRITE) {
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bio_endio(bio, 0);
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return DM_MAPIO_SUBMITTED;
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}
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goto map_bio;
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}
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/*
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* Default setting errors all I/O.
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*/
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return -EIO;
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}
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map_bio:
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flakey_map_bio(ti, bio);
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return DM_MAPIO_REMAPPED;
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}
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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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{
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unsigned sz = 0;
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struct flakey_c *fc = ti->private;
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unsigned drop_writes;
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switch (type) {
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case STATUSTYPE_INFO:
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result[0] = '\0';
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break;
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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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fc->down_interval);
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drop_writes = test_bit(DROP_WRITES, &fc->flags);
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DMEMIT("%u ", drop_writes);
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if (drop_writes)
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DMEMIT("drop_writes ");
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break;
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}
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return 0;
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}
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static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
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{
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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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}
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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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{
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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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return max_size;
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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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}
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static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
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{
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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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}
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static struct target_type flakey_target = {
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.name = "flakey",
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.version = {1, 2, 0},
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.module = THIS_MODULE,
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.ctr = flakey_ctr,
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.dtr = flakey_dtr,
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.map = flakey_map,
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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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};
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static int __init dm_flakey_init(void)
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{
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int r = dm_register_target(&flakey_target);
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if (r < 0)
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DMERR("register failed %d", r);
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return r;
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}
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static void __exit dm_flakey_exit(void)
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{
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dm_unregister_target(&flakey_target);
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}
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/* Module hooks */
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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");
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