/* $NetBSD: dm_target_snapshot.c,v 1.38 2020/01/21 16:27:53 tkusumi Exp $ */

/* $NetBSD: dm_target_snapshot.c,v 1.38 2020/01/21 16:27:53 tkusumi Exp $ */

/*
* Copyright (c) 2008 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Adam Hamsik.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: dm_target_snapshot.c,v 1.38 2020/01/21 16:27:53 tkusumi Exp $");

/*
* 1. Suspend my_data to temporarily stop any I/O while the snapshot is being
* activated.
* dmsetup suspend my_data
*
* 2. Create the snapshot-origin device with no table.
* dmsetup create my_data_org
*
* 3. Read the table from my_data and load it into my_data_org.
* dmsetup table my_data | dmsetup load my_data_org
*
* 4. Resume this new table.
* dmsetup resume my_data_org
*
* 5. Create the snapshot device with no table.
* dmsetup create my_data_snap
*
* 6. Load the table into my_data_snap. This uses /dev/hdd1 as the COW device and
* uses a 32kB chunk-size.
* echo "0 `blockdev --getsize /dev/mapper/my_data` snapshot \
* /dev/mapper/my_data_org /dev/hdd1 p 64" | dmsetup load my_data_snap
*
* 7. Reload my_data as a snapshot-origin device that points to my_data_org.
* echo "0 `blockdev --getsize /dev/mapper/my_data` snapshot-origin \
* /dev/mapper/my_data_org" | dmsetup load my_data
*
* 8. Resume the snapshot and origin devices.
* dmsetup resume my_data_snap
* dmsetup resume my_data
*
* Before snapshot creation
* dev_name; dev table
* | my_data; 0 1024 linear /dev/sd1a 384|
*
* After snapshot creation
* |my_data_org;0 1024 linear /dev/sd1a 384|
* /
* |my_data; 0 1024 snapshot-origin /dev/vg00/my_data_org|
* /
* |my_data_snap; 0 1024 snapshot /dev/vg00/my_data /dev/mapper/my_data_cow P 8
* \
* |my_data_cow; 0 256 linear /dev/sd1a 1408|
*/

/*
* This file implements initial version of device-mapper snapshot target.
*/
#include <sys/types.h>
#include <sys/param.h>
#include <sys/buf.h>
#include <sys/kmem.h>

#include "dm.h"

/* dm_target_snapshot.c */
int dm_target_snapshot_init(dm_table_entry_t *, int, char **);
char *dm_target_snapshot_table(void *);
int dm_target_snapshot_strategy(dm_table_entry_t *, struct buf *);
int dm_target_snapshot_sync(dm_table_entry_t *);
int dm_target_snapshot_destroy(dm_table_entry_t *);
//int dm_target_snapshot_upcall(dm_table_entry_t *, struct buf *);

/* dm snapshot origin driver */
int dm_target_snapshot_orig_init(dm_table_entry_t *, int, char **);
char *dm_target_snapshot_orig_table(void *);
int dm_target_snapshot_orig_strategy(dm_table_entry_t *, struct buf *);
int dm_target_snapshot_orig_sync(dm_table_entry_t *);
int dm_target_snapshot_orig_destroy(dm_table_entry_t *);
//int dm_target_snapshot_orig_upcall(dm_table_entry_t *, struct buf *);

typedef struct target_snapshot_config {
dm_pdev_t *tsc_snap_dev;
/* cow dev is set only for persistent snapshot devices */
dm_pdev_t *tsc_cow_dev;

uint64_t tsc_chunk_size;
uint32_t tsc_persistent_dev;
} dm_target_snapshot_config_t;

typedef struct target_snapshot_origin_config {
dm_pdev_t *tsoc_real_dev;
/* list of snapshots ? */
} dm_target_snapshot_origin_config_t;

#ifdef DM_TARGET_MODULE
/*
* Every target can be compiled directly to dm driver or as a
* separate module this part of target is used for loading targets
* to dm driver.
* Target can be unloaded from kernel only if there are no users of
* it e.g. there are no devices which uses that target.
*/
#include <sys/kernel.h>
#include <sys/module.h>

MODULE(MODULE_CLASS_MISC, dm_target_snapshot, "dm");

static int
dm_target_snapshot_modcmd(modcmd_t cmd, void *arg)
{
dm_target_t *dmt, *dmt1;
int r;

switch (cmd) {
case MODULE_CMD_INIT:
if (((dmt = dm_target_lookup("snapshot")) != NULL)) {
dm_target_unbusy(dmt);
return EEXIST;
}
if (((dmt = dm_target_lookup("snapshot-origin")) != NULL)) {
dm_target_unbusy(dmt);
return EEXIST;
}
dmt = dm_target_alloc("snapshot");
dmt1 = dm_target_alloc("snapshot-origin");

dmt->version[0] = 1;
dmt->version[1] = 0;
dmt->version[2] = 5;
dmt->init = &dm_target_snapshot_init;
dmt->table = &dm_target_snapshot_table;
dmt->strategy = &dm_target_snapshot_strategy;
dmt->sync = &dm_target_snapshot_sync;
dmt->destroy = &dm_target_snapshot_destroy;
//dmt->upcall = &dm_target_snapshot_upcall;

r = dm_target_insert(dmt);

dmt1->version[0] = 1;
dmt1->version[1] = 0;
dmt1->version[2] = 5;
dmt1->init = &dm_target_snapshot_orig_init;
dmt1->table = &dm_target_snapshot_orig_table;
dmt1->strategy = &dm_target_snapshot_orig_strategy;
dmt1->sync = &dm_target_snapshot_orig_sync;
dmt1->destroy = &dm_target_snapshot_orig_destroy;
//dmt1->upcall = &dm_target_snapshot_orig_upcall;

r = dm_target_insert(dmt1);
break;

case MODULE_CMD_FINI:
/*
* Try to remove snapshot target if it works remove snap-origin
* it is not possible to remove snapshot and do not remove
* snap-origin because they are used together.
*/
if ((r = dm_target_rem("snapshot")) == 0)
r = dm_target_rem("snapshot-origin");

break;

case MODULE_CMD_STAT:
return ENOTTY;

default:
return ENOTTY;
}

return r;
}
#endif

/*
* Init function called from dm_table_load_ioctl.
* argv: /dev/mapper/my_data_org /dev/mapper/tsc_cow_dev p 64
* snapshot_origin device, cow device, persistent flag, chunk size
*/
int
dm_target_snapshot_init(dm_table_entry_t *table_en, int argc, char **argv)
{
dm_target_snapshot_config_t *tsc;
dm_pdev_t *dmp_snap, *dmp_cow;

dmp_cow = NULL;

printf("Snapshot target init function called!!\n");
printf("Snapshotted device: %s, cow device %s,\n\t persistent flag: %s, "
"chunk size: %s\n", argv[0], argv[1], argv[2], argv[3]);

/* Insert snap device to global pdev list */
if ((dmp_snap = dm_pdev_insert(argv[0])) == NULL)
return ENOENT;

tsc = kmem_alloc(sizeof(*tsc), KM_SLEEP);
tsc->tsc_persistent_dev = 0;

/* There is now cow device for nonpersistent snapshot devices */
if (strcmp(argv[2], "p") == 0) {
tsc->tsc_persistent_dev = 1;

/* Insert cow device to global pdev list */
if ((dmp_cow = dm_pdev_insert(argv[1])) == NULL) {
kmem_free(tsc, sizeof(*tsc));
return ENOENT;
}
}
tsc->tsc_chunk_size = atoi64(argv[3]);

tsc->tsc_snap_dev = dmp_snap;
tsc->tsc_cow_dev = dmp_cow;

dm_table_add_deps(table_en, dmp_snap);
dm_table_add_deps(table_en, dmp_cow);
table_en->target_config = tsc;

return 0;
}

/*
* Table routine is called to get params string, which is target
* specific. When dm_table_status_ioctl is called with flag
* DM_STATUS_TABLE_FLAG I have to sent params string back.
*/
char *
dm_target_snapshot_table(void *target_config)
{
dm_target_snapshot_config_t *tsc;

uint32_t i;
uint32_t count;
size_t prm_len, cow_len;
char *params;

tsc = target_config;

prm_len = 0;
cow_len = 0;
count = 0;

printf("Snapshot target table function called\n");

/* count number of chars in offset */
for (i = tsc->tsc_chunk_size; i != 0; i /= 10)
count++;

if (tsc->tsc_persistent_dev)
cow_len = strlen(tsc->tsc_cow_dev->name);

/* length of names + count of chars + spaces and null char */
prm_len = strlen(tsc->tsc_snap_dev->name) + cow_len + count + 5;

params = kmem_alloc(prm_len, KM_SLEEP);

printf("%s %s %s %" PRIu64 "\n", tsc->tsc_snap_dev->name,
tsc->tsc_cow_dev->name, tsc->tsc_persistent_dev ? "p" : "n",
tsc->tsc_chunk_size);

snprintf(params, prm_len, "%s %s %s %" PRIu64, tsc->tsc_snap_dev->name,
tsc->tsc_persistent_dev ? tsc->tsc_cow_dev->name : "",
tsc->tsc_persistent_dev ? "p" : "n",
tsc->tsc_chunk_size);

return params;
}

/* Strategy routine called from dm_strategy. */
int
dm_target_snapshot_strategy(dm_table_entry_t *table_en, struct buf *bp)
{

bp->b_error = EIO;
bp->b_resid = 0;

biodone(bp);

return 0;
}

int
dm_target_snapshot_sync(dm_table_entry_t *table_en)
{

return 0;
}

/* Doesn't do anything here. */
int
dm_target_snapshot_destroy(dm_table_entry_t *table_en)
{

/*
* Destroy function is called for every target even if it
* doesn't have target_config.
*/
if (table_en->target_config == NULL)
goto out;

printf("Snapshot target destroy function called\n");

dm_target_snapshot_config_t *tsc = table_en->target_config;

/* Decrement pdev ref counter if 0 remove it */
dm_pdev_decr(tsc->tsc_snap_dev);
if (tsc->tsc_persistent_dev)
dm_pdev_decr(tsc->tsc_cow_dev);

kmem_free(tsc, sizeof(*tsc));
out:
/* Unbusy target so we can unload it */
dm_target_unbusy(table_en->target);

return 0;
}

#if 0
/* Upcall is used to inform other depended devices about IO. */
int
dm_target_snapshot_upcall(dm_table_entry_t *table_en, struct buf *bp)
{

printf("dm_target_snapshot_upcall called\n");

printf("upcall buf flags %s %s\n",
(bp->b_flags & B_WRITE) ? "B_WRITE" : "",
(bp->b_flags & B_READ) ? "B_READ" : "");

return 0;
}
#endif

/*
* dm target snapshot origin routines.
*
* Keep for compatibility with linux lvm2tools. They use two targets
* to implement snapshots. Snapshot target will implement exception
* store and snapshot origin will implement device which calls every
* snapshot device when write is done on master device.
*/

/*
* Init function called from dm_table_load_ioctl.
*
* argv: /dev/mapper/my_data_real
*/
int
dm_target_snapshot_orig_init(dm_table_entry_t *table_en, int argc, char **argv)
{
dm_target_snapshot_origin_config_t *tsoc;
dm_pdev_t *dmp_real;

printf("Snapshot origin target init function called!!\n");
printf("Parent device: %s\n", argv[0]);

/* Insert snap device to global pdev list */
if ((dmp_real = dm_pdev_insert(argv[0])) == NULL)
return ENOENT;

tsoc = kmem_alloc(sizeof(dm_target_snapshot_origin_config_t), KM_SLEEP);
tsoc->tsoc_real_dev = dmp_real;

dm_table_add_deps(table_en, dmp_real);
table_en->target_config = tsoc;

return 0;
}

/*
* Table routine is called to get params string, which is target
* specific. When dm_table_status_ioctl is called with flag
* DM_STATUS_TABLE_FLAG I have to sent params string back.
*/
char *
dm_target_snapshot_orig_table(void *target_config)
{
dm_target_snapshot_origin_config_t *tsoc;

size_t prm_len;
char *params;

tsoc = target_config;

prm_len = 0;

printf("Snapshot origin target table function called\n");

/* length of names + count of chars + spaces and null char */
prm_len = strlen(tsoc->tsoc_real_dev->name) + 1;

printf("real_dev name %s\n", tsoc->tsoc_real_dev->name);

params = kmem_alloc(prm_len, KM_SLEEP);

printf("%s\n", tsoc->tsoc_real_dev->name);

snprintf(params, prm_len, "%s", tsoc->tsoc_real_dev->name);

return params;
}

/* Strategy routine called from dm_strategy. */
int
dm_target_snapshot_orig_strategy(dm_table_entry_t *table_en, struct buf *bp)
{

bp->b_error = EIO;
bp->b_resid = 0;

biodone(bp);

return 0;
}

/*
* Sync underlying disk caches.
*/
int
dm_target_snapshot_orig_sync(dm_table_entry_t *table_en)
{
int cmd;
dm_target_snapshot_origin_config_t *tsoc;

tsoc = table_en->target_config;

cmd = 1;

return VOP_IOCTL(tsoc->tsoc_real_dev->pdev_vnode, DIOCCACHESYNC,
&cmd, FREAD|FWRITE, kauth_cred_get());
}

/* Decrement pdev and free allocated space. */
int
dm_target_snapshot_orig_destroy(dm_table_entry_t *table_en)
{

/*
* Destroy function is called for every target even if it
* doesn't have target_config.
*/

if (table_en->target_config == NULL)
goto out;

dm_target_snapshot_origin_config_t *tsoc = table_en->target_config;

/* Decrement pdev ref counter if 0 remove it */
dm_pdev_decr(tsoc->tsoc_real_dev);

kmem_free(tsoc, sizeof(*tsoc));
out:
/* Unbusy target so we can unload it */
dm_target_unbusy(table_en->target);

return 0;
}

#if 0
/* Unsupported for this target. */
int
dm_target_snapshot_orig_upcall(dm_table_entry_t *table_en, struct buf *bp)
{

return 0;
}
#endif