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linux/linux-5.18.11/drivers/md/dm-clone-target.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2019 Arrikto, Inc. All Rights Reserved.
*/
#include <linux/mm.h>
#include <linux/bio.h>
#include <linux/err.h>
#include <linux/hash.h>
#include <linux/list.h>
#include <linux/log2.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/dm-io.h>
#include <linux/mutex.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/blkdev.h>
#include <linux/kdev_t.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/jiffies.h>
#include <linux/mempool.h>
#include <linux/spinlock.h>
#include <linux/blk_types.h>
#include <linux/dm-kcopyd.h>
#include <linux/workqueue.h>
#include <linux/backing-dev.h>
#include <linux/device-mapper.h>
#include "dm.h"
#include "dm-clone-metadata.h"
#define DM_MSG_PREFIX "clone"
/*
* Minimum and maximum allowed region sizes
*/
#define MIN_REGION_SIZE (1 << 3) /* 4KB */
#define MAX_REGION_SIZE (1 << 21) /* 1GB */
#define MIN_HYDRATIONS 256 /* Size of hydration mempool */
#define DEFAULT_HYDRATION_THRESHOLD 1 /* 1 region */
#define DEFAULT_HYDRATION_BATCH_SIZE 1 /* Hydrate in batches of 1 region */
#define COMMIT_PERIOD HZ /* 1 sec */
/*
* Hydration hash table size: 1 << HASH_TABLE_BITS
*/
#define HASH_TABLE_BITS 15
DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(clone_hydration_throttle,
"A percentage of time allocated for hydrating regions");
/* Slab cache for struct dm_clone_region_hydration */
static struct kmem_cache *_hydration_cache;
/* dm-clone metadata modes */
enum clone_metadata_mode {
CM_WRITE, /* metadata may be changed */
CM_READ_ONLY, /* metadata may not be changed */
CM_FAIL, /* all metadata I/O fails */
};
struct hash_table_bucket;
struct clone {
struct dm_target *ti;
struct dm_dev *metadata_dev;
struct dm_dev *dest_dev;
struct dm_dev *source_dev;
unsigned long nr_regions;
sector_t region_size;
unsigned int region_shift;
/*
* A metadata commit and the actions taken in case it fails should run
* as a single atomic step.
*/
struct mutex commit_lock;
struct dm_clone_metadata *cmd;
/* Region hydration hash table */
struct hash_table_bucket *ht;
atomic_t ios_in_flight;
wait_queue_head_t hydration_stopped;
mempool_t hydration_pool;
unsigned long last_commit_jiffies;
/*
* We defer incoming WRITE bios for regions that are not hydrated,
* until after these regions have been hydrated.
*
* Also, we defer REQ_FUA and REQ_PREFLUSH bios, until after the
* metadata have been committed.
*/
spinlock_t lock;
struct bio_list deferred_bios;
struct bio_list deferred_discard_bios;
struct bio_list deferred_flush_bios;
struct bio_list deferred_flush_completions;
/* Maximum number of regions being copied during background hydration. */
unsigned int hydration_threshold;
/* Number of regions to batch together during background hydration. */
unsigned int hydration_batch_size;
/* Which region to hydrate next */
unsigned long hydration_offset;
atomic_t hydrations_in_flight;
/*
* Save a copy of the table line rather than reconstructing it for the
* status.
*/
unsigned int nr_ctr_args;
const char **ctr_args;
struct workqueue_struct *wq;
struct work_struct worker;
struct delayed_work waker;
struct dm_kcopyd_client *kcopyd_client;
enum clone_metadata_mode mode;
unsigned long flags;
};
/*
* dm-clone flags
*/
#define DM_CLONE_DISCARD_PASSDOWN 0
#define DM_CLONE_HYDRATION_ENABLED 1
#define DM_CLONE_HYDRATION_SUSPENDED 2
/*---------------------------------------------------------------------------*/
/*
* Metadata failure handling.
*/
static enum clone_metadata_mode get_clone_mode(struct clone *clone)
{
return READ_ONCE(clone->mode);
}
static const char *clone_device_name(struct clone *clone)
{
return dm_table_device_name(clone->ti->table);
}
static void __set_clone_mode(struct clone *clone, enum clone_metadata_mode new_mode)
{
static const char * const descs[] = {
"read-write",
"read-only",
"fail"
};
enum clone_metadata_mode old_mode = get_clone_mode(clone);
/* Never move out of fail mode */
if (old_mode == CM_FAIL)
new_mode = CM_FAIL;
switch (new_mode) {
case CM_FAIL:
case CM_READ_ONLY:
dm_clone_metadata_set_read_only(clone->cmd);
break;
case CM_WRITE:
dm_clone_metadata_set_read_write(clone->cmd);
break;
}
WRITE_ONCE(clone->mode, new_mode);
if (new_mode != old_mode) {
dm_table_event(clone->ti->table);
DMINFO("%s: Switching to %s mode", clone_device_name(clone),
descs[(int)new_mode]);
}
}
static void __abort_transaction(struct clone *clone)
{
const char *dev_name = clone_device_name(clone);
if (get_clone_mode(clone) >= CM_READ_ONLY)
return;
DMERR("%s: Aborting current metadata transaction", dev_name);
if (dm_clone_metadata_abort(clone->cmd)) {
DMERR("%s: Failed to abort metadata transaction", dev_name);
__set_clone_mode(clone, CM_FAIL);
}
}
static void __reload_in_core_bitset(struct clone *clone)
{
const char *dev_name = clone_device_name(clone);
if (get_clone_mode(clone) == CM_FAIL)
return;
/* Reload the on-disk bitset */
DMINFO("%s: Reloading on-disk bitmap", dev_name);
if (dm_clone_reload_in_core_bitset(clone->cmd)) {
DMERR("%s: Failed to reload on-disk bitmap", dev_name);
__set_clone_mode(clone, CM_FAIL);
}
}
static void __metadata_operation_failed(struct clone *clone, const char *op, int r)
{
DMERR("%s: Metadata operation `%s' failed: error = %d",
clone_device_name(clone), op, r);
__abort_transaction(clone);
__set_clone_mode(clone, CM_READ_ONLY);
/*
* dm_clone_reload_in_core_bitset() may run concurrently with either
* dm_clone_set_region_hydrated() or dm_clone_cond_set_range(), but
* it's safe as we have already set the metadata to read-only mode.
*/
__reload_in_core_bitset(clone);
}
/*---------------------------------------------------------------------------*/
/* Wake up anyone waiting for region hydrations to stop */
static inline void wakeup_hydration_waiters(struct clone *clone)
{
wake_up_all(&clone->hydration_stopped);
}
static inline void wake_worker(struct clone *clone)
{
queue_work(clone->wq, &clone->worker);
}
/*---------------------------------------------------------------------------*/
/*
* bio helper functions.
*/
static inline void remap_to_source(struct clone *clone, struct bio *bio)
{
bio_set_dev(bio, clone->source_dev->bdev);
}
static inline void remap_to_dest(struct clone *clone, struct bio *bio)
{
bio_set_dev(bio, clone->dest_dev->bdev);
}
static bool bio_triggers_commit(struct clone *clone, struct bio *bio)
{
return op_is_flush(bio->bi_opf) &&
dm_clone_changed_this_transaction(clone->cmd);
}
/* Get the address of the region in sectors */
static inline sector_t region_to_sector(struct clone *clone, unsigned long region_nr)
{
return ((sector_t)region_nr << clone->region_shift);
}
/* Get the region number of the bio */
static inline unsigned long bio_to_region(struct clone *clone, struct bio *bio)
{
return (bio->bi_iter.bi_sector >> clone->region_shift);
}
/* Get the region range covered by the bio */
static void bio_region_range(struct clone *clone, struct bio *bio,
unsigned long *rs, unsigned long *nr_regions)
{
unsigned long end;
*rs = dm_sector_div_up(bio->bi_iter.bi_sector, clone->region_size);
end = bio_end_sector(bio) >> clone->region_shift;
if (*rs >= end)
*nr_regions = 0;
else
*nr_regions = end - *rs;
}
/* Check whether a bio overwrites a region */
static inline bool is_overwrite_bio(struct clone *clone, struct bio *bio)
{
return (bio_data_dir(bio) == WRITE && bio_sectors(bio) == clone->region_size);
}
static void fail_bios(struct bio_list *bios, blk_status_t status)
{
struct bio *bio;
while ((bio = bio_list_pop(bios))) {
bio->bi_status = status;
bio_endio(bio);
}
}
static void submit_bios(struct bio_list *bios)
{
struct bio *bio;
struct blk_plug plug;
blk_start_plug(&plug);
while ((bio = bio_list_pop(bios)))
submit_bio_noacct(bio);
blk_finish_plug(&plug);
}
/*
* Submit bio to the underlying device.
*
* If the bio triggers a commit, delay it, until after the metadata have been
* committed.
*
* NOTE: The bio remapping must be performed by the caller.
*/
static void issue_bio(struct clone *clone, struct bio *bio)
{
if (!bio_triggers_commit(clone, bio)) {
submit_bio_noacct(bio);
return;
}
/*
* If the metadata mode is RO or FAIL we won't be able to commit the
* metadata, so we complete the bio with an error.
*/
if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) {
bio_io_error(bio);
return;
}
/*
* Batch together any bios that trigger commits and then issue a single
* commit for them in process_deferred_flush_bios().
*/
spin_lock_irq(&clone->lock);
bio_list_add(&clone->deferred_flush_bios, bio);
spin_unlock_irq(&clone->lock);
wake_worker(clone);
}
/*
* Remap bio to the destination device and submit it.
*
* If the bio triggers a commit, delay it, until after the metadata have been
* committed.
*/
static void remap_and_issue(struct clone *clone, struct bio *bio)
{
remap_to_dest(clone, bio);
issue_bio(clone, bio);
}
/*
* Issue bios that have been deferred until after their region has finished
* hydrating.
*
* We delegate the bio submission to the worker thread, so this is safe to call
* from interrupt context.
*/
static void issue_deferred_bios(struct clone *clone, struct bio_list *bios)
{
struct bio *bio;
unsigned long flags;
struct bio_list flush_bios = BIO_EMPTY_LIST;
struct bio_list normal_bios = BIO_EMPTY_LIST;
if (bio_list_empty(bios))
return;
while ((bio = bio_list_pop(bios))) {
if (bio_triggers_commit(clone, bio))
bio_list_add(&flush_bios, bio);
else
bio_list_add(&normal_bios, bio);
}
spin_lock_irqsave(&clone->lock, flags);
bio_list_merge(&clone->deferred_bios, &normal_bios);
bio_list_merge(&clone->deferred_flush_bios, &flush_bios);
spin_unlock_irqrestore(&clone->lock, flags);
wake_worker(clone);
}
static void complete_overwrite_bio(struct clone *clone, struct bio *bio)
{
unsigned long flags;
/*
* If the bio has the REQ_FUA flag set we must commit the metadata
* before signaling its completion.
*
* complete_overwrite_bio() is only called by hydration_complete(),
* after having successfully updated the metadata. This means we don't
* need to call dm_clone_changed_this_transaction() to check if the
* metadata has changed and thus we can avoid taking the metadata spin
* lock.
*/
if (!(bio->bi_opf & REQ_FUA)) {
bio_endio(bio);
return;
}
/*
* If the metadata mode is RO or FAIL we won't be able to commit the
* metadata, so we complete the bio with an error.
*/
if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) {
bio_io_error(bio);
return;
}
/*
* Batch together any bios that trigger commits and then issue a single
* commit for them in process_deferred_flush_bios().
*/
spin_lock_irqsave(&clone->lock, flags);
bio_list_add(&clone->deferred_flush_completions, bio);
spin_unlock_irqrestore(&clone->lock, flags);
wake_worker(clone);
}
static void trim_bio(struct bio *bio, sector_t sector, unsigned int len)
{
bio->bi_iter.bi_sector = sector;
bio->bi_iter.bi_size = to_bytes(len);
}
static void complete_discard_bio(struct clone *clone, struct bio *bio, bool success)
{
unsigned long rs, nr_regions;
/*
* If the destination device supports discards, remap and trim the
* discard bio and pass it down. Otherwise complete the bio
* immediately.
*/
if (test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags) && success) {
remap_to_dest(clone, bio);
bio_region_range(clone, bio, &rs, &nr_regions);
trim_bio(bio, region_to_sector(clone, rs),
nr_regions << clone->region_shift);
submit_bio_noacct(bio);
} else
bio_endio(bio);
}
static void process_discard_bio(struct clone *clone, struct bio *bio)
{
unsigned long rs, nr_regions;
bio_region_range(clone, bio, &rs, &nr_regions);
if (!nr_regions) {
bio_endio(bio);
return;
}
if (WARN_ON(rs >= clone->nr_regions || (rs + nr_regions) < rs ||
(rs + nr_regions) > clone->nr_regions)) {
DMERR("%s: Invalid range (%lu + %lu, total regions %lu) for discard (%llu + %u)",
clone_device_name(clone), rs, nr_regions,
clone->nr_regions,
(unsigned long long)bio->bi_iter.bi_sector,
bio_sectors(bio));
bio_endio(bio);
return;
}
/*
* The covered regions are already hydrated so we just need to pass
* down the discard.
*/
if (dm_clone_is_range_hydrated(clone->cmd, rs, nr_regions)) {
complete_discard_bio(clone, bio, true);
return;
}
/*
* If the metadata mode is RO or FAIL we won't be able to update the
* metadata for the regions covered by the discard so we just ignore
* it.
*/
if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) {
bio_endio(bio);
return;
}
/*
* Defer discard processing.
*/
spin_lock_irq(&clone->lock);
bio_list_add(&clone->deferred_discard_bios, bio);
spin_unlock_irq(&clone->lock);
wake_worker(clone);
}
/*---------------------------------------------------------------------------*/
/*
* dm-clone region hydrations.
*/
struct dm_clone_region_hydration {
struct clone *clone;
unsigned long region_nr;
struct bio *overwrite_bio;
bio_end_io_t *overwrite_bio_end_io;
struct bio_list deferred_bios;
blk_status_t status;
/* Used by hydration batching */
struct list_head list;
/* Used by hydration hash table */
struct hlist_node h;
};
/*
* Hydration hash table implementation.
*
* Ideally we would like to use list_bl, which uses bit spin locks and employs
* the least significant bit of the list head to lock the corresponding bucket,
* reducing the memory overhead for the locks. But, currently, list_bl and bit
* spin locks don't support IRQ safe versions. Since we have to take the lock
* in both process and interrupt context, we must fall back to using regular
* spin locks; one per hash table bucket.
*/
struct hash_table_bucket {
struct hlist_head head;
/* Spinlock protecting the bucket */
spinlock_t lock;
};
#define bucket_lock_irqsave(bucket, flags) \
spin_lock_irqsave(&(bucket)->lock, flags)
#define bucket_unlock_irqrestore(bucket, flags) \
spin_unlock_irqrestore(&(bucket)->lock, flags)
#define bucket_lock_irq(bucket) \
spin_lock_irq(&(bucket)->lock)
#define bucket_unlock_irq(bucket) \
spin_unlock_irq(&(bucket)->lock)
static int hash_table_init(struct clone *clone)
{
unsigned int i, sz;
struct hash_table_bucket *bucket;
sz = 1 << HASH_TABLE_BITS;
clone->ht = kvmalloc(sz * sizeof(struct hash_table_bucket), GFP_KERNEL);
if (!clone->ht)
return -ENOMEM;
for (i = 0; i < sz; i++) {
bucket = clone->ht + i;
INIT_HLIST_HEAD(&bucket->head);
spin_lock_init(&bucket->lock);
}
return 0;
}
static void hash_table_exit(struct clone *clone)
{
kvfree(clone->ht);
}
static struct hash_table_bucket *get_hash_table_bucket(struct clone *clone,
unsigned long region_nr)
{
return &clone->ht[hash_long(region_nr, HASH_TABLE_BITS)];
}
/*
* Search hash table for a hydration with hd->region_nr == region_nr
*
* NOTE: Must be called with the bucket lock held
*/
static struct dm_clone_region_hydration *__hash_find(struct hash_table_bucket *bucket,
unsigned long region_nr)
{
struct dm_clone_region_hydration *hd;
hlist_for_each_entry(hd, &bucket->head, h) {
if (hd->region_nr == region_nr)
return hd;
}
return NULL;
}
/*
* Insert a hydration into the hash table.
*
* NOTE: Must be called with the bucket lock held.
*/
static inline void __insert_region_hydration(struct hash_table_bucket *bucket,
struct dm_clone_region_hydration *hd)
{
hlist_add_head(&hd->h, &bucket->head);
}
/*
* This function inserts a hydration into the hash table, unless someone else
* managed to insert a hydration for the same region first. In the latter case
* it returns the existing hydration descriptor for this region.
*
* NOTE: Must be called with the hydration hash table lock held.
*/
static struct dm_clone_region_hydration *
__find_or_insert_region_hydration(struct hash_table_bucket *bucket,
struct dm_clone_region_hydration *hd)
{
struct dm_clone_region_hydration *hd2;
hd2 = __hash_find(bucket, hd->region_nr);
if (hd2)
return hd2;
__insert_region_hydration(bucket, hd);
return hd;
}
/*---------------------------------------------------------------------------*/
/* Allocate a hydration */
static struct dm_clone_region_hydration *alloc_hydration(struct clone *clone)
{
struct dm_clone_region_hydration *hd;
/*
* Allocate a hydration from the hydration mempool.
* This might block but it can't fail.
*/
hd = mempool_alloc(&clone->hydration_pool, GFP_NOIO);
hd->clone = clone;
return hd;
}
static inline void free_hydration(struct dm_clone_region_hydration *hd)
{
mempool_free(hd, &hd->clone->hydration_pool);
}
/* Initialize a hydration */
static void hydration_init(struct dm_clone_region_hydration *hd, unsigned long region_nr)
{
hd->region_nr = region_nr;
hd->overwrite_bio = NULL;
bio_list_init(&hd->deferred_bios);
hd->status = 0;
INIT_LIST_HEAD(&hd->list);
INIT_HLIST_NODE(&hd->h);
}
/*---------------------------------------------------------------------------*/
/*
* Update dm-clone's metadata after a region has finished hydrating and remove
* hydration from the hash table.
*/
static int hydration_update_metadata(struct dm_clone_region_hydration *hd)
{
int r = 0;
unsigned long flags;
struct hash_table_bucket *bucket;
struct clone *clone = hd->clone;
if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY))
r = -EPERM;
/* Update the metadata */
if (likely(!r) && hd->status == BLK_STS_OK)
r = dm_clone_set_region_hydrated(clone->cmd, hd->region_nr);
bucket = get_hash_table_bucket(clone, hd->region_nr);
/* Remove hydration from hash table */
bucket_lock_irqsave(bucket, flags);
hlist_del(&hd->h);
bucket_unlock_irqrestore(bucket, flags);
return r;
}
/*
* Complete a region's hydration:
*
* 1. Update dm-clone's metadata.
* 2. Remove hydration from hash table.
* 3. Complete overwrite bio.
* 4. Issue deferred bios.
* 5. If this was the last hydration, wake up anyone waiting for
* hydrations to finish.
*/
static void hydration_complete(struct dm_clone_region_hydration *hd)
{
int r;
blk_status_t status;
struct clone *clone = hd->clone;
r = hydration_update_metadata(hd);
if (hd->status == BLK_STS_OK && likely(!r)) {
if (hd->overwrite_bio)
complete_overwrite_bio(clone, hd->overwrite_bio);
issue_deferred_bios(clone, &hd->deferred_bios);
} else {
status = r ? BLK_STS_IOERR : hd->status;
if (hd->overwrite_bio)
bio_list_add(&hd->deferred_bios, hd->overwrite_bio);
fail_bios(&hd->deferred_bios, status);
}
free_hydration(hd);
if (atomic_dec_and_test(&clone->hydrations_in_flight))
wakeup_hydration_waiters(clone);
}
static void hydration_kcopyd_callback(int read_err, unsigned long write_err, void *context)
{
blk_status_t status;
struct dm_clone_region_hydration *tmp, *hd = context;
struct clone *clone = hd->clone;
LIST_HEAD(batched_hydrations);
if (read_err || write_err) {
DMERR_LIMIT("%s: hydration failed", clone_device_name(clone));
status = BLK_STS_IOERR;
} else {
status = BLK_STS_OK;
}
list_splice_tail(&hd->list, &batched_hydrations);
hd->status = status;
hydration_complete(hd);
/* Complete batched hydrations */
list_for_each_entry_safe(hd, tmp, &batched_hydrations, list) {
hd->status = status;
hydration_complete(hd);
}
/* Continue background hydration, if there is no I/O in-flight */
if (test_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags) &&
!atomic_read(&clone->ios_in_flight))
wake_worker(clone);
}
static void hydration_copy(struct dm_clone_region_hydration *hd, unsigned int nr_regions)
{
unsigned long region_start, region_end;
sector_t tail_size, region_size, total_size;
struct dm_io_region from, to;
struct clone *clone = hd->clone;
if (WARN_ON(!nr_regions))
return;
region_size = clone->region_size;
region_start = hd->region_nr;
region_end = region_start + nr_regions - 1;
total_size = region_to_sector(clone, nr_regions - 1);
if (region_end == clone->nr_regions - 1) {
/*
* The last region of the target might be smaller than
* region_size.
*/
tail_size = clone->ti->len & (region_size - 1);
if (!tail_size)
tail_size = region_size;
} else {
tail_size = region_size;
}
total_size += tail_size;
from.bdev = clone->source_dev->bdev;
from.sector = region_to_sector(clone, region_start);
from.count = total_size;
to.bdev = clone->dest_dev->bdev;
to.sector = from.sector;
to.count = from.count;
/* Issue copy */
atomic_add(nr_regions, &clone->hydrations_in_flight);
dm_kcopyd_copy(clone->kcopyd_client, &from, 1, &to, 0,
hydration_kcopyd_callback, hd);
}
static void overwrite_endio(struct bio *bio)
{
struct dm_clone_region_hydration *hd = bio->bi_private;
bio->bi_end_io = hd->overwrite_bio_end_io;
hd->status = bio->bi_status;
hydration_complete(hd);
}
static void hydration_overwrite(struct dm_clone_region_hydration *hd, struct bio *bio)
{
/*
* We don't need to save and restore bio->bi_private because device
* mapper core generates a new bio for us to use, with clean
* bi_private.
*/
hd->overwrite_bio = bio;
hd->overwrite_bio_end_io = bio->bi_end_io;
bio->bi_end_io = overwrite_endio;
bio->bi_private = hd;
atomic_inc(&hd->clone->hydrations_in_flight);
submit_bio_noacct(bio);
}
/*
* Hydrate bio's region.
*
* This function starts the hydration of the bio's region and puts the bio in
* the list of deferred bios for this region. In case, by the time this
* function is called, the region has finished hydrating it's submitted to the
* destination device.
*
* NOTE: The bio remapping must be performed by the caller.
*/
static void hydrate_bio_region(struct clone *clone, struct bio *bio)
{
unsigned long region_nr;
struct hash_table_bucket *bucket;
struct dm_clone_region_hydration *hd, *hd2;
region_nr = bio_to_region(clone, bio);
bucket = get_hash_table_bucket(clone, region_nr);
bucket_lock_irq(bucket);
hd = __hash_find(bucket, region_nr);
if (hd) {
/* Someone else is hydrating the region */
bio_list_add(&hd->deferred_bios, bio);
bucket_unlock_irq(bucket);
return;
}
if (dm_clone_is_region_hydrated(clone->cmd, region_nr)) {
/* The region has been hydrated */
bucket_unlock_irq(bucket);
issue_bio(clone, bio);
return;
}
/*
* We must allocate a hydration descriptor and start the hydration of
* the corresponding region.
*/
bucket_unlock_irq(bucket);
hd = alloc_hydration(clone);
hydration_init(hd, region_nr);
bucket_lock_irq(bucket);
/* Check if the region has been hydrated in the meantime. */
if (dm_clone_is_region_hydrated(clone->cmd, region_nr)) {
bucket_unlock_irq(bucket);
free_hydration(hd);
issue_bio(clone, bio);
return;
}
hd2 = __find_or_insert_region_hydration(bucket, hd);
if (hd2 != hd) {
/* Someone else started the region's hydration. */
bio_list_add(&hd2->deferred_bios, bio);
bucket_unlock_irq(bucket);
free_hydration(hd);
return;
}
/*
* If the metadata mode is RO or FAIL then there is no point starting a
* hydration, since we will not be able to update the metadata when the
* hydration finishes.
*/
if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) {
hlist_del(&hd->h);
bucket_unlock_irq(bucket);
free_hydration(hd);
bio_io_error(bio);
return;
}
/*
* Start region hydration.
*
* If a bio overwrites a region, i.e., its size is equal to the
* region's size, then we don't need to copy the region from the source
* to the destination device.
*/
if (is_overwrite_bio(clone, bio)) {
bucket_unlock_irq(bucket);
hydration_overwrite(hd, bio);
} else {
bio_list_add(&hd->deferred_bios, bio);
bucket_unlock_irq(bucket);
hydration_copy(hd, 1);
}
}
/*---------------------------------------------------------------------------*/
/*
* Background hydrations.
*/
/*
* Batch region hydrations.
*
* To better utilize device bandwidth we batch together the hydration of
* adjacent regions. This allows us to use small region sizes, e.g., 4KB, which
* is good for small, random write performance (because of the overwriting of
* un-hydrated regions) and at the same time issue big copy requests to kcopyd
* to achieve high hydration bandwidth.
*/
struct batch_info {
struct dm_clone_region_hydration *head;
unsigned int nr_batched_regions;
};
static void __batch_hydration(struct batch_info *batch,
struct dm_clone_region_hydration *hd)
{
struct clone *clone = hd->clone;
unsigned int max_batch_size = READ_ONCE(clone->hydration_batch_size);
if (batch->head) {
/* Try to extend the current batch */
if (batch->nr_batched_regions < max_batch_size &&
(batch->head->region_nr + batch->nr_batched_regions) == hd->region_nr) {
list_add_tail(&hd->list, &batch->head->list);
batch->nr_batched_regions++;
hd = NULL;
}
/* Check if we should issue the current batch */
if (batch->nr_batched_regions >= max_batch_size || hd) {
hydration_copy(batch->head, batch->nr_batched_regions);
batch->head = NULL;
batch->nr_batched_regions = 0;
}
}
if (!hd)
return;
/* We treat max batch sizes of zero and one equivalently */
if (max_batch_size <= 1) {
hydration_copy(hd, 1);
return;
}
/* Start a new batch */
BUG_ON(!list_empty(&hd->list));
batch->head = hd;
batch->nr_batched_regions = 1;
}
static unsigned long __start_next_hydration(struct clone *clone,
unsigned long offset,
struct batch_info *batch)
{
struct hash_table_bucket *bucket;
struct dm_clone_region_hydration *hd;
unsigned long nr_regions = clone->nr_regions;
hd = alloc_hydration(clone);
/* Try to find a region to hydrate. */
do {
offset = dm_clone_find_next_unhydrated_region(clone->cmd, offset);
if (offset == nr_regions)
break;
bucket = get_hash_table_bucket(clone, offset);
bucket_lock_irq(bucket);
if (!dm_clone_is_region_hydrated(clone->cmd, offset) &&
!__hash_find(bucket, offset)) {
hydration_init(hd, offset);
__insert_region_hydration(bucket, hd);
bucket_unlock_irq(bucket);
/* Batch hydration */
__batch_hydration(batch, hd);
return (offset + 1);
}
bucket_unlock_irq(bucket);
} while (++offset < nr_regions);
if (hd)
free_hydration(hd);
return offset;
}
/*
* This function searches for regions that still reside in the source device
* and starts their hydration.
*/
static void do_hydration(struct clone *clone)
{
unsigned int current_volume;
unsigned long offset, nr_regions = clone->nr_regions;
struct batch_info batch = {
.head = NULL,
.nr_batched_regions = 0,
};
if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY))
return;
if (dm_clone_is_hydration_done(clone->cmd))
return;
/*
* Avoid race with device suspension.
*/
atomic_inc(&clone->hydrations_in_flight);
/*
* Make sure atomic_inc() is ordered before test_bit(), otherwise we
* might race with clone_postsuspend() and start a region hydration
* after the target has been suspended.
*
* This is paired with the smp_mb__after_atomic() in
* clone_postsuspend().
*/
smp_mb__after_atomic();
offset = clone->hydration_offset;
while (likely(!test_bit(DM_CLONE_HYDRATION_SUSPENDED, &clone->flags)) &&
!atomic_read(&clone->ios_in_flight) &&
test_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags) &&
offset < nr_regions) {
current_volume = atomic_read(&clone->hydrations_in_flight);
current_volume += batch.nr_batched_regions;
if (current_volume > READ_ONCE(clone->hydration_threshold))
break;
offset = __start_next_hydration(clone, offset, &batch);
}
if (batch.head)
hydration_copy(batch.head, batch.nr_batched_regions);
if (offset >= nr_regions)
offset = 0;
clone->hydration_offset = offset;
if (atomic_dec_and_test(&clone->hydrations_in_flight))
wakeup_hydration_waiters(clone);
}
/*---------------------------------------------------------------------------*/
static bool need_commit_due_to_time(struct clone *clone)
{
return !time_in_range(jiffies, clone->last_commit_jiffies,
clone->last_commit_jiffies + COMMIT_PERIOD);
}
/*
* A non-zero return indicates read-only or fail mode.
*/
static int commit_metadata(struct clone *clone, bool *dest_dev_flushed)
{
int r = 0;
if (dest_dev_flushed)
*dest_dev_flushed = false;
mutex_lock(&clone->commit_lock);
if (!dm_clone_changed_this_transaction(clone->cmd))
goto out;
if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY)) {
r = -EPERM;
goto out;
}
r = dm_clone_metadata_pre_commit(clone->cmd);
if (unlikely(r)) {
__metadata_operation_failed(clone, "dm_clone_metadata_pre_commit", r);
goto out;
}
r = blkdev_issue_flush(clone->dest_dev->bdev);
if (unlikely(r)) {
__metadata_operation_failed(clone, "flush destination device", r);
goto out;
}
if (dest_dev_flushed)
*dest_dev_flushed = true;
r = dm_clone_metadata_commit(clone->cmd);
if (unlikely(r)) {
__metadata_operation_failed(clone, "dm_clone_metadata_commit", r);
goto out;
}
if (dm_clone_is_hydration_done(clone->cmd))
dm_table_event(clone->ti->table);
out:
mutex_unlock(&clone->commit_lock);
return r;
}
static void process_deferred_discards(struct clone *clone)
{
int r = -EPERM;
struct bio *bio;
struct blk_plug plug;
unsigned long rs, nr_regions;
struct bio_list discards = BIO_EMPTY_LIST;
spin_lock_irq(&clone->lock);
bio_list_merge(&discards, &clone->deferred_discard_bios);
bio_list_init(&clone->deferred_discard_bios);
spin_unlock_irq(&clone->lock);
if (bio_list_empty(&discards))
return;
if (unlikely(get_clone_mode(clone) >= CM_READ_ONLY))
goto out;
/* Update the metadata */
bio_list_for_each(bio, &discards) {
bio_region_range(clone, bio, &rs, &nr_regions);
/*
* A discard request might cover regions that have been already
* hydrated. There is no need to update the metadata for these
* regions.
*/
r = dm_clone_cond_set_range(clone->cmd, rs, nr_regions);
if (unlikely(r))
break;
}
out:
blk_start_plug(&plug);
while ((bio = bio_list_pop(&discards)))
complete_discard_bio(clone, bio, r == 0);
blk_finish_plug(&plug);
}
static void process_deferred_bios(struct clone *clone)
{
struct bio_list bios = BIO_EMPTY_LIST;
spin_lock_irq(&clone->lock);
bio_list_merge(&bios, &clone->deferred_bios);
bio_list_init(&clone->deferred_bios);
spin_unlock_irq(&clone->lock);
if (bio_list_empty(&bios))
return;
submit_bios(&bios);
}
static void process_deferred_flush_bios(struct clone *clone)
{
struct bio *bio;
bool dest_dev_flushed;
struct bio_list bios = BIO_EMPTY_LIST;
struct bio_list bio_completions = BIO_EMPTY_LIST;
/*
* If there are any deferred flush bios, we must commit the metadata
* before issuing them or signaling their completion.
*/
spin_lock_irq(&clone->lock);
bio_list_merge(&bios, &clone->deferred_flush_bios);
bio_list_init(&clone->deferred_flush_bios);
bio_list_merge(&bio_completions, &clone->deferred_flush_completions);
bio_list_init(&clone->deferred_flush_completions);
spin_unlock_irq(&clone->lock);
if (bio_list_empty(&bios) && bio_list_empty(&bio_completions) &&
!(dm_clone_changed_this_transaction(clone->cmd) && need_commit_due_to_time(clone)))
return;
if (commit_metadata(clone, &dest_dev_flushed)) {
bio_list_merge(&bios, &bio_completions);
while ((bio = bio_list_pop(&bios)))
bio_io_error(bio);
return;
}
clone->last_commit_jiffies = jiffies;
while ((bio = bio_list_pop(&bio_completions)))
bio_endio(bio);
while ((bio = bio_list_pop(&bios))) {
if ((bio->bi_opf & REQ_PREFLUSH) && dest_dev_flushed) {
/* We just flushed the destination device as part of
* the metadata commit, so there is no reason to send
* another flush.
*/
bio_endio(bio);
} else {
submit_bio_noacct(bio);
}
}
}
static void do_worker(struct work_struct *work)
{
struct clone *clone = container_of(work, typeof(*clone), worker);
process_deferred_bios(clone);
process_deferred_discards(clone);
/*
* process_deferred_flush_bios():
*
* - Commit metadata
*
* - Process deferred REQ_FUA completions
*
* - Process deferred REQ_PREFLUSH bios
*/
process_deferred_flush_bios(clone);
/* Background hydration */
do_hydration(clone);
}
/*
* Commit periodically so that not too much unwritten data builds up.
*
* Also, restart background hydration, if it has been stopped by in-flight I/O.
*/
static void do_waker(struct work_struct *work)
{
struct clone *clone = container_of(to_delayed_work(work), struct clone, waker);
wake_worker(clone);
queue_delayed_work(clone->wq, &clone->waker, COMMIT_PERIOD);
}
/*---------------------------------------------------------------------------*/
/*
* Target methods
*/
static int clone_map(struct dm_target *ti, struct bio *bio)
{
struct clone *clone = ti->private;
unsigned long region_nr;
atomic_inc(&clone->ios_in_flight);
if (unlikely(get_clone_mode(clone) == CM_FAIL))
return DM_MAPIO_KILL;
/*
* REQ_PREFLUSH bios carry no data:
*
* - Commit metadata, if changed
*
* - Pass down to destination device
*/
if (bio->bi_opf & REQ_PREFLUSH) {
remap_and_issue(clone, bio);
return DM_MAPIO_SUBMITTED;
}
bio->bi_iter.bi_sector = dm_target_offset(ti, bio->bi_iter.bi_sector);
/*
* dm-clone interprets discards and performs a fast hydration of the
* discarded regions, i.e., we skip the copy from the source device and
* just mark the regions as hydrated.
*/
if (bio_op(bio) == REQ_OP_DISCARD) {
process_discard_bio(clone, bio);
return DM_MAPIO_SUBMITTED;
}
/*
* If the bio's region is hydrated, redirect it to the destination
* device.
*
* If the region is not hydrated and the bio is a READ, redirect it to
* the source device.
*
* Else, defer WRITE bio until after its region has been hydrated and
* start the region's hydration immediately.
*/
region_nr = bio_to_region(clone, bio);
if (dm_clone_is_region_hydrated(clone->cmd, region_nr)) {
remap_and_issue(clone, bio);
return DM_MAPIO_SUBMITTED;
} else if (bio_data_dir(bio) == READ) {
remap_to_source(clone, bio);
return DM_MAPIO_REMAPPED;
}
remap_to_dest(clone, bio);
hydrate_bio_region(clone, bio);
return DM_MAPIO_SUBMITTED;
}
static int clone_endio(struct dm_target *ti, struct bio *bio, blk_status_t *error)
{
struct clone *clone = ti->private;
atomic_dec(&clone->ios_in_flight);
return DM_ENDIO_DONE;
}
static void emit_flags(struct clone *clone, char *result, unsigned int maxlen,
ssize_t *sz_ptr)
{
ssize_t sz = *sz_ptr;
unsigned int count;
count = !test_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags);
count += !test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags);
DMEMIT("%u ", count);
if (!test_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags))
DMEMIT("no_hydration ");
if (!test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags))
DMEMIT("no_discard_passdown ");
*sz_ptr = sz;
}
static void emit_core_args(struct clone *clone, char *result,
unsigned int maxlen, ssize_t *sz_ptr)
{
ssize_t sz = *sz_ptr;
unsigned int count = 4;
DMEMIT("%u hydration_threshold %u hydration_batch_size %u ", count,
READ_ONCE(clone->hydration_threshold),
READ_ONCE(clone->hydration_batch_size));
*sz_ptr = sz;
}
/*
* Status format:
*
* <metadata block size> <#used metadata blocks>/<#total metadata blocks>
* <clone region size> <#hydrated regions>/<#total regions> <#hydrating regions>
* <#features> <features>* <#core args> <core args>* <clone metadata mode>
*/
static void clone_status(struct dm_target *ti, status_type_t type,
unsigned int status_flags, char *result,
unsigned int maxlen)
{
int r;
unsigned int i;
ssize_t sz = 0;
dm_block_t nr_free_metadata_blocks = 0;
dm_block_t nr_metadata_blocks = 0;
char buf[BDEVNAME_SIZE];
struct clone *clone = ti->private;
switch (type) {
case STATUSTYPE_INFO:
if (get_clone_mode(clone) == CM_FAIL) {
DMEMIT("Fail");
break;
}
/* Commit to ensure statistics aren't out-of-date */
if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti))
(void) commit_metadata(clone, NULL);
r = dm_clone_get_free_metadata_block_count(clone->cmd, &nr_free_metadata_blocks);
if (r) {
DMERR("%s: dm_clone_get_free_metadata_block_count returned %d",
clone_device_name(clone), r);
goto error;
}
r = dm_clone_get_metadata_dev_size(clone->cmd, &nr_metadata_blocks);
if (r) {
DMERR("%s: dm_clone_get_metadata_dev_size returned %d",
clone_device_name(clone), r);
goto error;
}
DMEMIT("%u %llu/%llu %llu %u/%lu %u ",
DM_CLONE_METADATA_BLOCK_SIZE,
(unsigned long long)(nr_metadata_blocks - nr_free_metadata_blocks),
(unsigned long long)nr_metadata_blocks,
(unsigned long long)clone->region_size,
dm_clone_nr_of_hydrated_regions(clone->cmd),
clone->nr_regions,
atomic_read(&clone->hydrations_in_flight));
emit_flags(clone, result, maxlen, &sz);
emit_core_args(clone, result, maxlen, &sz);
switch (get_clone_mode(clone)) {
case CM_WRITE:
DMEMIT("rw");
break;
case CM_READ_ONLY:
DMEMIT("ro");
break;
case CM_FAIL:
DMEMIT("Fail");
}
break;
case STATUSTYPE_TABLE:
format_dev_t(buf, clone->metadata_dev->bdev->bd_dev);
DMEMIT("%s ", buf);
format_dev_t(buf, clone->dest_dev->bdev->bd_dev);
DMEMIT("%s ", buf);
format_dev_t(buf, clone->source_dev->bdev->bd_dev);
DMEMIT("%s", buf);
for (i = 0; i < clone->nr_ctr_args; i++)
DMEMIT(" %s", clone->ctr_args[i]);
break;
case STATUSTYPE_IMA:
*result = '\0';
break;
}
return;
error:
DMEMIT("Error");
}
static sector_t get_dev_size(struct dm_dev *dev)
{
return bdev_nr_sectors(dev->bdev);
}
/*---------------------------------------------------------------------------*/
/*
* Construct a clone device mapping:
*
* clone <metadata dev> <destination dev> <source dev> <region size>
* [<#feature args> [<feature arg>]* [<#core args> [key value]*]]
*
* metadata dev: Fast device holding the persistent metadata
* destination dev: The destination device, which will become a clone of the
* source device
* source dev: The read-only source device that gets cloned
* region size: dm-clone unit size in sectors
*
* #feature args: Number of feature arguments passed
* feature args: E.g. no_hydration, no_discard_passdown
*
* #core arguments: An even number of core arguments
* core arguments: Key/value pairs for tuning the core
* E.g. 'hydration_threshold 256'
*/
static int parse_feature_args(struct dm_arg_set *as, struct clone *clone)
{
int r;
unsigned int argc;
const char *arg_name;
struct dm_target *ti = clone->ti;
const struct dm_arg args = {
.min = 0,
.max = 2,
.error = "Invalid number of feature arguments"
};
/* No feature arguments supplied */
if (!as->argc)
return 0;
r = dm_read_arg_group(&args, as, &argc, &ti->error);
if (r)
return r;
while (argc) {
arg_name = dm_shift_arg(as);
argc--;
if (!strcasecmp(arg_name, "no_hydration")) {
__clear_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags);
} else if (!strcasecmp(arg_name, "no_discard_passdown")) {
__clear_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags);
} else {
ti->error = "Invalid feature argument";
return -EINVAL;
}
}
return 0;
}
static int parse_core_args(struct dm_arg_set *as, struct clone *clone)
{
int r;
unsigned int argc;
unsigned int value;
const char *arg_name;
struct dm_target *ti = clone->ti;
const struct dm_arg args = {
.min = 0,
.max = 4,
.error = "Invalid number of core arguments"
};
/* Initialize core arguments */
clone->hydration_batch_size = DEFAULT_HYDRATION_BATCH_SIZE;
clone->hydration_threshold = DEFAULT_HYDRATION_THRESHOLD;
/* No core arguments supplied */
if (!as->argc)
return 0;
r = dm_read_arg_group(&args, as, &argc, &ti->error);
if (r)
return r;
if (argc & 1) {
ti->error = "Number of core arguments must be even";
return -EINVAL;
}
while (argc) {
arg_name = dm_shift_arg(as);
argc -= 2;
if (!strcasecmp(arg_name, "hydration_threshold")) {
if (kstrtouint(dm_shift_arg(as), 10, &value)) {
ti->error = "Invalid value for argument `hydration_threshold'";
return -EINVAL;
}
clone->hydration_threshold = value;
} else if (!strcasecmp(arg_name, "hydration_batch_size")) {
if (kstrtouint(dm_shift_arg(as), 10, &value)) {
ti->error = "Invalid value for argument `hydration_batch_size'";
return -EINVAL;
}
clone->hydration_batch_size = value;
} else {
ti->error = "Invalid core argument";
return -EINVAL;
}
}
return 0;
}
static int parse_region_size(struct clone *clone, struct dm_arg_set *as, char **error)
{
int r;
unsigned int region_size;
struct dm_arg arg;
arg.min = MIN_REGION_SIZE;
arg.max = MAX_REGION_SIZE;
arg.error = "Invalid region size";
r = dm_read_arg(&arg, as, &region_size, error);
if (r)
return r;
/* Check region size is a power of 2 */
if (!is_power_of_2(region_size)) {
*error = "Region size is not a power of 2";
return -EINVAL;
}
/* Validate the region size against the device logical block size */
if (region_size % (bdev_logical_block_size(clone->source_dev->bdev) >> 9) ||
region_size % (bdev_logical_block_size(clone->dest_dev->bdev) >> 9)) {
*error = "Region size is not a multiple of device logical block size";
return -EINVAL;
}
clone->region_size = region_size;
return 0;
}
static int validate_nr_regions(unsigned long n, char **error)
{
/*
* dm_bitset restricts us to 2^32 regions. test_bit & co. restrict us
* further to 2^31 regions.
*/
if (n > (1UL << 31)) {
*error = "Too many regions. Consider increasing the region size";
return -EINVAL;
}
return 0;
}
static int parse_metadata_dev(struct clone *clone, struct dm_arg_set *as, char **error)
{
int r;
sector_t metadata_dev_size;
r = dm_get_device(clone->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
&clone->metadata_dev);
if (r) {
*error = "Error opening metadata device";
return r;
}
metadata_dev_size = get_dev_size(clone->metadata_dev);
if (metadata_dev_size > DM_CLONE_METADATA_MAX_SECTORS_WARNING)
DMWARN("Metadata device %pg is larger than %u sectors: excess space will not be used.",
clone->metadata_dev->bdev, DM_CLONE_METADATA_MAX_SECTORS);
return 0;
}
static int parse_dest_dev(struct clone *clone, struct dm_arg_set *as, char **error)
{
int r;
sector_t dest_dev_size;
r = dm_get_device(clone->ti, dm_shift_arg(as), FMODE_READ | FMODE_WRITE,
&clone->dest_dev);
if (r) {
*error = "Error opening destination device";
return r;
}
dest_dev_size = get_dev_size(clone->dest_dev);
if (dest_dev_size < clone->ti->len) {
dm_put_device(clone->ti, clone->dest_dev);
*error = "Device size larger than destination device";
return -EINVAL;
}
return 0;
}
static int parse_source_dev(struct clone *clone, struct dm_arg_set *as, char **error)
{
int r;
sector_t source_dev_size;
r = dm_get_device(clone->ti, dm_shift_arg(as), FMODE_READ,
&clone->source_dev);
if (r) {
*error = "Error opening source device";
return r;
}
source_dev_size = get_dev_size(clone->source_dev);
if (source_dev_size < clone->ti->len) {
dm_put_device(clone->ti, clone->source_dev);
*error = "Device size larger than source device";
return -EINVAL;
}
return 0;
}
static int copy_ctr_args(struct clone *clone, int argc, const char **argv, char **error)
{
unsigned int i;
const char **copy;
copy = kcalloc(argc, sizeof(*copy), GFP_KERNEL);
if (!copy)
goto error;
for (i = 0; i < argc; i++) {
copy[i] = kstrdup(argv[i], GFP_KERNEL);
if (!copy[i]) {
while (i--)
kfree(copy[i]);
kfree(copy);
goto error;
}
}
clone->nr_ctr_args = argc;
clone->ctr_args = copy;
return 0;
error:
*error = "Failed to allocate memory for table line";
return -ENOMEM;
}
static int clone_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
int r;
sector_t nr_regions;
struct clone *clone;
struct dm_arg_set as;
if (argc < 4) {
ti->error = "Invalid number of arguments";
return -EINVAL;
}
as.argc = argc;
as.argv = argv;
clone = kzalloc(sizeof(*clone), GFP_KERNEL);
if (!clone) {
ti->error = "Failed to allocate clone structure";
return -ENOMEM;
}
clone->ti = ti;
/* Initialize dm-clone flags */
__set_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags);
__set_bit(DM_CLONE_HYDRATION_SUSPENDED, &clone->flags);
__set_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags);
r = parse_metadata_dev(clone, &as, &ti->error);
if (r)
goto out_with_clone;
r = parse_dest_dev(clone, &as, &ti->error);
if (r)
goto out_with_meta_dev;
r = parse_source_dev(clone, &as, &ti->error);
if (r)
goto out_with_dest_dev;
r = parse_region_size(clone, &as, &ti->error);
if (r)
goto out_with_source_dev;
clone->region_shift = __ffs(clone->region_size);
nr_regions = dm_sector_div_up(ti->len, clone->region_size);
/* Check for overflow */
if (nr_regions != (unsigned long)nr_regions) {
ti->error = "Too many regions. Consider increasing the region size";
r = -EOVERFLOW;
goto out_with_source_dev;
}
clone->nr_regions = nr_regions;
r = validate_nr_regions(clone->nr_regions, &ti->error);
if (r)
goto out_with_source_dev;
r = dm_set_target_max_io_len(ti, clone->region_size);
if (r) {
ti->error = "Failed to set max io len";
goto out_with_source_dev;
}
r = parse_feature_args(&as, clone);
if (r)
goto out_with_source_dev;
r = parse_core_args(&as, clone);
if (r)
goto out_with_source_dev;
/* Load metadata */
clone->cmd = dm_clone_metadata_open(clone->metadata_dev->bdev, ti->len,
clone->region_size);
if (IS_ERR(clone->cmd)) {
ti->error = "Failed to load metadata";
r = PTR_ERR(clone->cmd);
goto out_with_source_dev;
}
__set_clone_mode(clone, CM_WRITE);
if (get_clone_mode(clone) != CM_WRITE) {
ti->error = "Unable to get write access to metadata, please check/repair metadata";
r = -EPERM;
goto out_with_metadata;
}
clone->last_commit_jiffies = jiffies;
/* Allocate hydration hash table */
r = hash_table_init(clone);
if (r) {
ti->error = "Failed to allocate hydration hash table";
goto out_with_metadata;
}
atomic_set(&clone->ios_in_flight, 0);
init_waitqueue_head(&clone->hydration_stopped);
spin_lock_init(&clone->lock);
bio_list_init(&clone->deferred_bios);
bio_list_init(&clone->deferred_discard_bios);
bio_list_init(&clone->deferred_flush_bios);
bio_list_init(&clone->deferred_flush_completions);
clone->hydration_offset = 0;
atomic_set(&clone->hydrations_in_flight, 0);
clone->wq = alloc_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM, 0);
if (!clone->wq) {
ti->error = "Failed to allocate workqueue";
r = -ENOMEM;
goto out_with_ht;
}
INIT_WORK(&clone->worker, do_worker);
INIT_DELAYED_WORK(&clone->waker, do_waker);
clone->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
if (IS_ERR(clone->kcopyd_client)) {
r = PTR_ERR(clone->kcopyd_client);
goto out_with_wq;
}
r = mempool_init_slab_pool(&clone->hydration_pool, MIN_HYDRATIONS,
_hydration_cache);
if (r) {
ti->error = "Failed to create dm_clone_region_hydration memory pool";
goto out_with_kcopyd;
}
/* Save a copy of the table line */
r = copy_ctr_args(clone, argc - 3, (const char **)argv + 3, &ti->error);
if (r)
goto out_with_mempool;
mutex_init(&clone->commit_lock);
/* Enable flushes */
ti->num_flush_bios = 1;
ti->flush_supported = true;
/* Enable discards */
ti->discards_supported = true;
ti->num_discard_bios = 1;
ti->private = clone;
return 0;
out_with_mempool:
mempool_exit(&clone->hydration_pool);
out_with_kcopyd:
dm_kcopyd_client_destroy(clone->kcopyd_client);
out_with_wq:
destroy_workqueue(clone->wq);
out_with_ht:
hash_table_exit(clone);
out_with_metadata:
dm_clone_metadata_close(clone->cmd);
out_with_source_dev:
dm_put_device(ti, clone->source_dev);
out_with_dest_dev:
dm_put_device(ti, clone->dest_dev);
out_with_meta_dev:
dm_put_device(ti, clone->metadata_dev);
out_with_clone:
kfree(clone);
return r;
}
static void clone_dtr(struct dm_target *ti)
{
unsigned int i;
struct clone *clone = ti->private;
mutex_destroy(&clone->commit_lock);
for (i = 0; i < clone->nr_ctr_args; i++)
kfree(clone->ctr_args[i]);
kfree(clone->ctr_args);
mempool_exit(&clone->hydration_pool);
dm_kcopyd_client_destroy(clone->kcopyd_client);
destroy_workqueue(clone->wq);
hash_table_exit(clone);
dm_clone_metadata_close(clone->cmd);
dm_put_device(ti, clone->source_dev);
dm_put_device(ti, clone->dest_dev);
dm_put_device(ti, clone->metadata_dev);
kfree(clone);
}
/*---------------------------------------------------------------------------*/
static void clone_postsuspend(struct dm_target *ti)
{
struct clone *clone = ti->private;
/*
* To successfully suspend the device:
*
* - We cancel the delayed work for periodic commits and wait for
* it to finish.
*
* - We stop the background hydration, i.e. we prevent new region
* hydrations from starting.
*
* - We wait for any in-flight hydrations to finish.
*
* - We flush the workqueue.
*
* - We commit the metadata.
*/
cancel_delayed_work_sync(&clone->waker);
set_bit(DM_CLONE_HYDRATION_SUSPENDED, &clone->flags);
/*
* Make sure set_bit() is ordered before atomic_read(), otherwise we
* might race with do_hydration() and miss some started region
* hydrations.
*
* This is paired with smp_mb__after_atomic() in do_hydration().
*/
smp_mb__after_atomic();
wait_event(clone->hydration_stopped, !atomic_read(&clone->hydrations_in_flight));
flush_workqueue(clone->wq);
(void) commit_metadata(clone, NULL);
}
static void clone_resume(struct dm_target *ti)
{
struct clone *clone = ti->private;
clear_bit(DM_CLONE_HYDRATION_SUSPENDED, &clone->flags);
do_waker(&clone->waker.work);
}
static bool bdev_supports_discards(struct block_device *bdev)
{
struct request_queue *q = bdev_get_queue(bdev);
return (q && blk_queue_discard(q));
}
/*
* If discard_passdown was enabled verify that the destination device supports
* discards. Disable discard_passdown if not.
*/
static void disable_passdown_if_not_supported(struct clone *clone)
{
struct block_device *dest_dev = clone->dest_dev->bdev;
struct queue_limits *dest_limits = &bdev_get_queue(dest_dev)->limits;
const char *reason = NULL;
if (!test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags))
return;
if (!bdev_supports_discards(dest_dev))
reason = "discard unsupported";
else if (dest_limits->max_discard_sectors < clone->region_size)
reason = "max discard sectors smaller than a region";
if (reason) {
DMWARN("Destination device (%pd) %s: Disabling discard passdown.",
dest_dev, reason);
clear_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags);
}
}
static void set_discard_limits(struct clone *clone, struct queue_limits *limits)
{
struct block_device *dest_bdev = clone->dest_dev->bdev;
struct queue_limits *dest_limits = &bdev_get_queue(dest_bdev)->limits;
if (!test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags)) {
/* No passdown is done so we set our own virtual limits */
limits->discard_granularity = clone->region_size << SECTOR_SHIFT;
limits->max_discard_sectors = round_down(UINT_MAX >> SECTOR_SHIFT, clone->region_size);
return;
}
/*
* clone_iterate_devices() is stacking both the source and destination
* device limits but discards aren't passed to the source device, so
* inherit destination's limits.
*/
limits->max_discard_sectors = dest_limits->max_discard_sectors;
limits->max_hw_discard_sectors = dest_limits->max_hw_discard_sectors;
limits->discard_granularity = dest_limits->discard_granularity;
limits->discard_alignment = dest_limits->discard_alignment;
limits->discard_misaligned = dest_limits->discard_misaligned;
limits->max_discard_segments = dest_limits->max_discard_segments;
}
static void clone_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
struct clone *clone = ti->private;
u64 io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;
/*
* If the system-determined stacked limits are compatible with
* dm-clone's region size (io_opt is a factor) do not override them.
*/
if (io_opt_sectors < clone->region_size ||
do_div(io_opt_sectors, clone->region_size)) {
blk_limits_io_min(limits, clone->region_size << SECTOR_SHIFT);
blk_limits_io_opt(limits, clone->region_size << SECTOR_SHIFT);
}
disable_passdown_if_not_supported(clone);
set_discard_limits(clone, limits);
}
static int clone_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
int ret;
struct clone *clone = ti->private;
struct dm_dev *dest_dev = clone->dest_dev;
struct dm_dev *source_dev = clone->source_dev;
ret = fn(ti, source_dev, 0, ti->len, data);
if (!ret)
ret = fn(ti, dest_dev, 0, ti->len, data);
return ret;
}
/*
* dm-clone message functions.
*/
static void set_hydration_threshold(struct clone *clone, unsigned int nr_regions)
{
WRITE_ONCE(clone->hydration_threshold, nr_regions);
/*
* If user space sets hydration_threshold to zero then the hydration
* will stop. If at a later time the hydration_threshold is increased
* we must restart the hydration process by waking up the worker.
*/
wake_worker(clone);
}
static void set_hydration_batch_size(struct clone *clone, unsigned int nr_regions)
{
WRITE_ONCE(clone->hydration_batch_size, nr_regions);
}
static void enable_hydration(struct clone *clone)
{
if (!test_and_set_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags))
wake_worker(clone);
}
static void disable_hydration(struct clone *clone)
{
clear_bit(DM_CLONE_HYDRATION_ENABLED, &clone->flags);
}
static int clone_message(struct dm_target *ti, unsigned int argc, char **argv,
char *result, unsigned int maxlen)
{
struct clone *clone = ti->private;
unsigned int value;
if (!argc)
return -EINVAL;
if (!strcasecmp(argv[0], "enable_hydration")) {
enable_hydration(clone);
return 0;
}
if (!strcasecmp(argv[0], "disable_hydration")) {
disable_hydration(clone);
return 0;
}
if (argc != 2)
return -EINVAL;
if (!strcasecmp(argv[0], "hydration_threshold")) {
if (kstrtouint(argv[1], 10, &value))
return -EINVAL;
set_hydration_threshold(clone, value);
return 0;
}
if (!strcasecmp(argv[0], "hydration_batch_size")) {
if (kstrtouint(argv[1], 10, &value))
return -EINVAL;
set_hydration_batch_size(clone, value);
return 0;
}
DMERR("%s: Unsupported message `%s'", clone_device_name(clone), argv[0]);
return -EINVAL;
}
static struct target_type clone_target = {
.name = "clone",
.version = {1, 0, 0},
.module = THIS_MODULE,
.ctr = clone_ctr,
.dtr = clone_dtr,
.map = clone_map,
.end_io = clone_endio,
.postsuspend = clone_postsuspend,
.resume = clone_resume,
.status = clone_status,
.message = clone_message,
.io_hints = clone_io_hints,
.iterate_devices = clone_iterate_devices,
};
/*---------------------------------------------------------------------------*/
/* Module functions */
static int __init dm_clone_init(void)
{
int r;
_hydration_cache = KMEM_CACHE(dm_clone_region_hydration, 0);
if (!_hydration_cache)
return -ENOMEM;
r = dm_register_target(&clone_target);
if (r < 0) {
DMERR("Failed to register clone target");
return r;
}
return 0;
}
static void __exit dm_clone_exit(void)
{
dm_unregister_target(&clone_target);
kmem_cache_destroy(_hydration_cache);
_hydration_cache = NULL;
}
/* Module hooks */
module_init(dm_clone_init);
module_exit(dm_clone_exit);
MODULE_DESCRIPTION(DM_NAME " clone target");
MODULE_AUTHOR("Nikos Tsironis <ntsironis@arrikto.com>");
MODULE_LICENSE("GPL");
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