/*
* Copyright (C) 2002 Sistina Software (UK) Limited.
*
* This file is released under the GPL.
*
* Kcopyd provides a simple interface for copying an area of one
* block-device to one or more other block-devices, with an asynchronous
* completion notification.
*/
#include <asm/atomic.h>
#include <linux/blkdev.h>
#include <linux/config.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/workqueue.h>
#include "kcopyd.h"
static struct workqueue_struct *_kcopyd_wq;
static struct work_struct _kcopyd_work;
static inline void wake(void)
{
queue_work(_kcopyd_wq, &_kcopyd_work);
}
/*-----------------------------------------------------------------
* Each kcopyd client has its own little pool of preallocated
* pages for kcopyd io.
*---------------------------------------------------------------*/
struct kcopyd_client {
struct list_head list;
spinlock_t lock;
struct page_list *pages;
unsigned int nr_pages;
unsigned int nr_free_pages;
};
static struct page_list *alloc_pl(void)
{
struct page_list *pl;
pl = kmalloc(sizeof(*pl), GFP_KERNEL);
if (!pl)
return NULL;
pl->page = alloc_page(GFP_KERNEL);
if (!pl->page) {
kfree(pl);
return NULL;
}
return pl;
}
static void free_pl(struct page_list *pl)
{
__free_page(pl->page);
kfree(pl);
}
static int kcopyd_get_pages(struct kcopyd_client *kc,
unsigned int nr, struct page_list **pages)
{
struct page_list *pl;
spin_lock(&kc->lock);
if (kc->nr_free_pages < nr) {
spin_unlock(&kc->lock);
return -ENOMEM;
}
kc->nr_free_pages -= nr;
for (*pages = pl = kc->pages; --nr; pl = pl->next)
;
kc->pages = pl->next;
pl->next = NULL;
spin_unlock(&kc->lock);
return 0;
}
static void kcopyd_put_pages(struct kcopyd_client *kc, struct page_list *pl)
{
struct page_list *cursor;
spin_lock(&kc->lock);
for (cursor = pl; cursor->next; cursor = cursor->next)
kc->nr_free_pages++;
kc->nr_free_pages++;
cursor->next = kc->pages;
kc->pages = pl;
spin_unlock(&kc->lock);
}
/*
* These three functions resize the page pool.
*/
static void drop_pages(struct page_list *pl)
{
struct page_list *next;
while (pl) {
next = pl->next;
free_pl(pl);
pl = next;
}
}
static int client_alloc_pages(struct kcopyd_client *kc, unsigned int nr)
{
unsigned int i;
struct page_list *pl = NULL, *next;
for (i = 0; i < nr; i++) {
next = alloc_pl();
if (!next) {
if (pl)
drop_pages(pl);
return -ENOMEM;
}
next->next = pl;
pl = next;
}
kcopyd_put_pages(kc, pl);
kc->nr_pages += nr;
return 0;
}
static void client_free_pages(struct kcopyd_client *kc)
{
BUG_ON(kc->nr_free_pages != kc->nr_pages);
drop_pages(kc->pages);
kc->pages = NULL;
kc->nr_free_pages = kc->nr_pages = 0;
}
/*-----------------------------------------------------------------
* kcopyd_jobs need to be allocated by the *clients* of kcopyd,
* for this reason we use a mempool to prevent the client from
* ever having to do io (which could cause a deadlock).
*---------------------------------------------------------------*/
struct kcopyd_job {
struct kcopyd_client *kc;
struct list_head list;
unsigned long flags;
/*
* Error state of the job.
*/
int read_err;
unsigned int write_err;
/*
* Either READ or WRITE
*/
int rw;
struct io_region source;
/*
* The destinations for the transfer.
*/
unsigned int num_dests;
struct io_region dests[KCOPYD_MAX_REGIONS];
sector_t offset;
unsigned int nr_pages;
struct page_list *pages;
/*
* Set this to ensure you are notified when the job has
* completed. 'context' is for callback to use.
*/
kcopyd_notify_fn fn;
void *context;
/*
* These fields are only used if the job has been split
* into more manageable parts.
*/
struct semaphore lock;
atomic_t sub_jobs;
sector_t progress;
};
/* FIXME: this should scale with the number of pages */
#define MIN_JOBS 512
static kmem_cache_t *_job_cache;
static mempool_t *_job_pool;
/*
* We maintain three lists of jobs:
*
* i) jobs waiting for pages
* ii) jobs that have pages, and are waiting for the io to be issued.
* iii) jobs that have completed.
*
* All three of these are protected by job_lock.
*/
static DEFINE_SPINLOCK(_job_lock);
static LIST_HEAD(_complete_jobs);
static LIST_HEAD(_io_jobs);
static LIST_HEAD(_pages_jobs);
static int jobs_init(void)
{
_job_cache = kmem_cache_create("kcopyd-jobs",
sizeof(struct kcopyd_job),
__alignof__(struct kcopyd_job),
0, NULL, NULL);
if (!_job_cache)
return -ENOMEM;
_job_pool = mempool_create(MIN_JOBS, mempool_alloc_slab,
mempool_free_slab, _job_cache);
if (!_job_pool) {
kmem_cache_destroy(_job_cache);
return -ENOMEM;
}
return 0;
}
static void jobs_exit(void)
{
BUG_ON(!list_empty(&_complete_jobs));
BUG_ON(!list_empty(&_io_jobs));
BUG_ON(!list_empty(&_pages_jobs));
mempool_destroy(_job_pool);
kmem_cache_destroy(_job_cache);
_job_pool = NULL;
_job_cache = NULL;
}
/*
* Functions to push and pop a job onto the head of a given job
* list.
*/
static inline struct kcopyd_job *pop(struct list_head *jobs)
{
struct kcopyd_job *job = NULL;
unsigned long flags;
spin_lock_irqsave(&_job_lock, flags);
if (!list_empty(jobs)) {
job = list_entry(jobs->next, struct kcopyd_job, list);
list_del(&job->list);
}
spin_unlock_irqrestore(&_job_lock, flags);
return job;
}
static inline void push(struct list_head *jobs, struct kcopyd_job *job)
{
unsigned long flags;
spin_lock_irqsave(&_job_lock, flags);
list_add_tail(&job->list, jobs);
spin_unlock_irqrestore(&_job_lock, flags);
}
/*
* These three functions process 1 item from the corresponding
* job list.
*
* They return:
* < 0: error
* 0: success
* > 0: can't process yet.
*/
static int run_complete_job(struct kcopyd_job *job)
{
void *context = job->context;
int read_err = job->read_err;
unsigned int write_err = job->write_err;
kcopyd_notify_fn fn = job->fn;
kcopyd_put_pages(job->kc, job->pages);
mempool_free(job, _job_pool);
fn(read_err, write_err, context);
return 0;
}
static void complete_io(unsigned long error, void *context)
{
struct kcopyd_job *job = (struct kcopyd_job *) context;
if (error) {
if (job->rw == WRITE)
job->write_err &= error;
else
job->read_err = 1;
if (!test_bit(KCOPYD_IGNORE_ERROR, &job->flags)) {
push(&_complete_jobs, job);
wake();
return;
}
}
if (job->rw == WRITE)
push(&_complete_jobs, job);
else {
job->rw = WRITE;
push(&_io_jobs, job);
}
wake();
}
/*
* Request io on as many buffer heads as we can currently get for
* a particular job.
*/
static int run_io_job(struct kcopyd_job *job)
{
int r;
if (job->rw == READ)
r = dm_io_async(1, &job->source, job->rw,
job->pages,
job->offset, complete_io, job);
else
r = dm_io_async(job->num_dests, job->dests, job->rw,
job->pages,
job->offset, complete_io, job);
return r;
}
static int run_pages_job(struct kcopyd_job *job)
{
int r;
job->nr_pages = dm_div_up(job->dests[0].count + job->offset,
PAGE_SIZE >> 9);
r = kcopyd_get_pages(job->kc, job->nr_pages, &job->pages);
if (!r) {
/* this job is ready for io */
push(&_io_jobs, job);
return 0;
}
if (r == -ENOMEM)
/* can't complete now */
return 1;
return r;
}
/*
* Run through a list for as long as possible. Returns the count
* of successful jobs.
*/
static int process_jobs(struct list_head *jobs, int (*fn) (struct kcopyd_job *))
{
struct kcopyd_job *job;
int r, count = 0;
while ((job = pop(jobs))) {
r = fn(job);
if (r < 0) {
/* error this rogue job */
if (job->rw == WRITE)
job->write_err = (unsigned int) -1;
else
job->read_err = 1;
push(&_complete_jobs, job);
break;
}
if (r > 0) {
/*
* We couldn't service this job ATM, so
* push this job back onto the list.
*/
push(jobs, job);
break;
}
count++;
}
return count;
}
/*
* kcopyd does this every time it's woken up.
*/
static void do_work(void *ignored)
{
/*
* The order that these are called is *very* important.
* complete jobs can free some pages for pages jobs.
* Pages jobs when successful will jump onto the io jobs
* list. io jobs call wake when they complete and it all
* starts again.
*/
process_jobs(&_complete_jobs, run_complete_job);
process_jobs(&_pages_jobs, run_pages_job);
process_jobs(&_io_jobs, run_io_job);
}
/*
* If we are copying a small region we just dispatch a single job
* to do the copy, otherwise the io has to be split up into many
* jobs.
*/
static void dispatch_job(struct kcopyd_job *job)
{
push(&_pages_jobs, job);
wake();
}
#define SUB_JOB_SIZE 128
static void segment_complete(int read_err,
unsigned int write_err, void *context)
{
/* FIXME: tidy this function */
sector_t progress = 0;
sector_t count = 0;
struct kcopyd_job *job = (struct kcopyd_job *) context;
down(&job->lock);
/* update the error */
if (read_err)
job->read_err = 1;
if (write_err)
job->write_err &= write_err;
/*
* Only dispatch more work if there hasn't been an error.
*/
if ((!job->read_err && !job->write_err) ||
test_bit(KCOPYD_IGNORE_ERROR, &job->flags)) {
/* get the next chunk of work */
progress = job->progress;
count = job->source.count - progress;
if (count) {
if (count > SUB_JOB_SIZE)
count = SUB_JOB_SIZE;
job->progress += count;
}
}
up(&job->lock);
if (count) {
int i;
struct kcopyd_job *sub_job = mempool_alloc(_job_pool, GFP_NOIO);
*sub_job = *job;
sub_job->source.sector += progress;
sub_job->source.count = count;
for (i = 0; i < job->num_dests; i++) {
sub_job->dests[i].sector += progress;
sub_job->dests[i].count = count;
}
sub_job->fn = segment_complete;
sub_job->context = job;
dispatch_job(sub_job);
} else if (atomic_dec_and_test(&job->sub_jobs)) {
/*
* To avoid a race we must keep the job around
* until after the notify function has completed.
* Otherwise the client may try and stop the job
* after we've completed.
*/
job->fn(read_err, write_err, job->context);
mempool_free(job, _job_pool);
}
}
/*
* Create some little jobs that will do the move between
* them.
*/
#define SPLIT_COUNT 8
static void split_job(struct kcopyd_job *job)
{
int i;
atomic_set(&job->sub_jobs, SPLIT_COUNT);
for (i = 0; i < SPLIT_COUNT; i++)
segment_complete(0, 0u, job);
}
int kcopyd_copy(struct kcopyd_client *kc, struct io_region *from,
unsigned int num_dests, struct io_region *dests,
unsigned int flags, kcopyd_notify_fn fn, void *context)
{
struct kcopyd_job *job;
/*
* Allocate a new job.
*/
job = mempool_alloc(_job_pool, GFP_NOIO);
/*
* set up for the read.
*/
job->kc = kc;
job->flags = flags;
job->read_err = 0;
job->write_err = 0;
job->rw = READ;
job->source = *from;
job->num_dests = num_dests;
memcpy(&job->dests, dests, sizeof(*dests) * num_dests);
job->offset = 0;
job->nr_pages = 0;
job->pages = NULL;
job->fn = fn;
job->context = context;
if (job->source.count < SUB_JOB_SIZE)
dispatch_job(job);
else {
init_MUTEX(&job->lock);
job->progress = 0;
split_job(job);
}
return 0;
}
/*
* Cancels a kcopyd job, eg. someone might be deactivating a
* mirror.
*/
int kcopyd_cancel(struct kcopyd_job *job, int block)
{
/* FIXME: finish */
return -1;
}
/*-----------------------------------------------------------------
* Unit setup
*---------------------------------------------------------------*/
static DECLARE_MUTEX(_client_lock);
static LIST_HEAD(_clients);
static void client_add(struct kcopyd_client *kc)
{
down(&_client_lock);
list_add(&kc->list, &_clients);
up(&_client_lock);
}
static void client_del(struct kcopyd_client *kc)
{
down(&_client_lock);
list_del(&kc->list);
up(&_client_lock);
}
static DECLARE_MUTEX(kcopyd_init_lock);
static int kcopyd_clients = 0;
static int kcopyd_init(void)
{
int r;
down(&kcopyd_init_lock);
if (kcopyd_clients) {
/* Already initialized. */
kcopyd_clients++;
up(&kcopyd_init_lock);
return 0;
}
r = jobs_init();
if (r) {
up(&kcopyd_init_lock);
return r;
}
_kcopyd_wq = create_singlethread_workqueue("kcopyd");
if (!_kcopyd_wq) {
jobs_exit();
up(&kcopyd_init_lock);
return -ENOMEM;
}
kcopyd_clients++;
INIT_WORK(&_kcopyd_work, do_work, NULL);
up(&kcopyd_init_lock);
return 0;
}
static void kcopyd_exit(void)
{
down(&kcopyd_init_lock);
kcopyd_clients--;
if (!kcopyd_clients) {
jobs_exit();
destroy_workqueue(_kcopyd_wq);
_kcopyd_wq = NULL;
}
up(&kcopyd_init_lock);
}
int kcopyd_client_create(unsigned int nr_pages, struct kcopyd_client **result)
{
int r = 0;
struct kcopyd_client *kc;
r = kcopyd_init();
if (r)
return r;
kc = kmalloc(sizeof(*kc), GFP_KERNEL);
if (!kc) {
kcopyd_exit();
return -ENOMEM;
}
spin_lock_init(&kc->lock);
kc->pages = NULL;
kc->nr_pages = kc->nr_free_pages = 0;
r = client_alloc_pages(kc, nr_pages);
if (r) {
kfree(kc);
kcopyd_exit();
return r;
}
r = dm_io_get(nr_pages);
if (r) {
client_free_pages(kc);
kfree(kc);
kcopyd_exit();
return r;
}
client_add(kc);
*result = kc;
return 0;
}
void kcopyd_client_destroy(struct kcopyd_client *kc)
{
dm_io_put(kc->nr_pages);
client_free_pages(kc);
client_del(kc);
kfree(kc);
kcopyd_exit();
}
EXPORT_SYMBOL(kcopyd_client_create);
EXPORT_SYMBOL(kcopyd_client_destroy);
EXPORT_SYMBOL(kcopyd_copy);
EXPORT_SYMBOL(kcopyd_cancel);
