- 根目录:
- drivers
- md
- dm-kcopyd.c
/*
* Copyright (C) 2002 Sistina Software (UK) Limited.
* Copyright (C) 2006 Red Hat GmbH
*
* 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 <linux/types.h>
#include <linux/atomic.h>
#include <linux/blkdev.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 <linux/mutex.h>
#include <linux/device-mapper.h>
#include <linux/dm-kcopyd.h>
#include "dm.h"
#define SUB_JOB_SIZE 128
#define SPLIT_COUNT 8
#define MIN_JOBS 8
#define RESERVE_PAGES (DIV_ROUND_UP(SUB_JOB_SIZE << SECTOR_SHIFT, PAGE_SIZE))
/*-----------------------------------------------------------------
* Each kcopyd client has its own little pool of preallocated
* pages for kcopyd io.
*---------------------------------------------------------------*/
struct dm_kcopyd_client {
struct page_list *pages;
unsigned nr_reserved_pages;
unsigned nr_free_pages;
struct dm_io_client *io_client;
wait_queue_head_t destroyq;
atomic_t nr_jobs;
mempool_t *job_pool;
struct workqueue_struct *kcopyd_wq;
struct work_struct kcopyd_work;
/*
* 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.
*/
spinlock_t job_lock;
struct list_head complete_jobs;
struct list_head io_jobs;
struct list_head pages_jobs;
};
static struct page_list zero_page_list;
static void wake(struct dm_kcopyd_client *kc)
{
queue_work(kc->kcopyd_wq, &kc->kcopyd_work);
}
/*
* Obtain one page for the use of kcopyd.
*/
static struct page_list *alloc_pl(gfp_t gfp)
{
struct page_list *pl;
pl = kmalloc(sizeof(*pl), gfp);
if (!pl)
return NULL;
pl->page = alloc_page(gfp);
if (!pl->page) {
kfree(pl);
return NULL;
}
return pl;
}
static void free_pl(struct page_list *pl)
{
__free_page(pl->page);
kfree(pl);
}
/*
* Add the provided pages to a client's free page list, releasing
* back to the system any beyond the reserved_pages limit.
*/
static void kcopyd_put_pages(struct dm_kcopyd_client *kc, struct page_list *pl)
{
struct page_list *next;
do {
next = pl->next;
if (kc->nr_free_pages >= kc->nr_reserved_pages)
free_pl(pl);
else {
pl->next = kc->pages;
kc->pages = pl;
kc->nr_free_pages++;
}
pl = next;
} while (pl);
}
static int kcopyd_get_pages(struct dm_kcopyd_client *kc,
unsigned int nr, struct page_list **pages)
{
struct page_list *pl;
*pages = NULL;
do {
pl = alloc_pl(__GFP_NOWARN | __GFP_NORETRY);
if (unlikely(!pl)) {
/* Use reserved pages */
pl = kc->pages;
if (unlikely(!pl))
goto out_of_memory;
kc->pages = pl->next;
kc->nr_free_pages--;
}
pl->next = *pages;
*pages = pl;
} while (--nr);
return 0;
out_of_memory:
if (*pages)
kcopyd_put_pages(kc, *pages);
return -ENOMEM;
}
/*
* 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;
}
}
/*
* Allocate and reserve nr_pages for the use of a specific client.
*/
static int client_reserve_pages(struct dm_kcopyd_client *kc, unsigned nr_pages)
{
unsigned i;
struct page_list *pl = NULL, *next;
for (i = 0; i < nr_pages; i++) {
next = alloc_pl(GFP_KERNEL);
if (!next) {
if (pl)
drop_pages(pl);
return -ENOMEM;
}
next->next = pl;
pl = next;
}
kc->nr_reserved_pages += nr_pages;
kcopyd_put_pages(kc, pl);
return 0;
}
static void client_free_pages(struct dm_kcopyd_client *kc)
{
BUG_ON(kc->nr_free_pages != kc->nr_reserved_pages);
drop_pages(kc->pages);
kc->pages = NULL;
kc->nr_free_pages = kc->nr_reserved_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 dm_kcopyd_client *kc;
struct list_head list;
unsigned long flags;
/*
* Error state of the job.
*/
int read_err;
unsigned long write_err;
/*
* Either READ or WRITE
*/
int rw;
struct dm_io_region source;
/*
* The destinations for the transfer.
*/
unsigned int num_dests;
struct dm_io_region dests[DM_KCOPYD_MAX_REGIONS];
struct page_list *pages;
/*
* Set this to ensure you are notified when the job has
* completed. 'context' is for callback to use.
*/
dm_kcopyd_notify_fn fn;
void *context;
/*
* These fields are only used if the job has been split
* into more manageable parts.
*/
struct mutex lock;
atomic_t sub_jobs;
sector_t progress;
struct kcopyd_job *master_job;
};
static struct kmem_cache *_job_cache;
int __init dm_kcopyd_init(void)
{
_job_cache = kmem_cache_create("kcopyd_job",
sizeof(struct kcopyd_job) * (SPLIT_COUNT + 1),
__alignof__(struct kcopyd_job), 0, NULL);
if (!_job_cache)
return -ENOMEM;
zero_page_list.next = &zero_page_list;
zero_page_list.page = ZERO_PAGE(0);
return 0;
}
void dm_kcopyd_exit(void)
{
kmem_cache_destroy(_job_cache);
_job_cache = NULL;
}
/*
* Functions to push and pop a job onto the head of a given job
* list.
*/
static struct kcopyd_job *pop(struct list_head *jobs,
struct dm_kcopyd_client *kc)
{
struct kcopyd_job *job = NULL;
unsigned long flags;
spin_lock_irqsave(&kc->job_lock, flags);
if (!list_empty(jobs)) {
job = list_entry(jobs->next, struct kcopyd_job, list);
list_del(&job->list);
}
spin_unlock_irqrestore(&kc->job_lock, flags);
return job;
}
static void push(struct list_head *jobs, struct kcopyd_job *job)
{
unsigned long flags;
struct dm_kcopyd_client *kc = job->kc;
spin_lock_irqsave(&kc->job_lock, flags);
list_add_tail(&job->list, jobs);
spin_unlock_irqrestore(&kc->job_lock, flags);
}
static void push_head(struct list_head *jobs, struct kcopyd_job *job)
{
unsigned long flags;
struct dm_kcopyd_client *kc = job->kc;
spin_lock_irqsave(&kc->job_lock, flags);
list_add(&job->list, jobs);
spin_unlock_irqrestore(&kc->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 long write_err = job->write_err;
dm_kcopyd_notify_fn fn = job->fn;
struct dm_kcopyd_client *kc = job->kc;
if (job->pages && job->pages != &zero_page_list)
kcopyd_put_pages(kc, job->pages);
/*
* If this is the master job, the sub jobs have already
* completed so we can free everything.
*/
if (job->master_job == job)
mempool_free(job, kc->job_pool);
fn(read_err, write_err, context);
if (atomic_dec_and_test(&kc->nr_jobs))
wake_up(&kc->destroyq);
return 0;
}
static void complete_io(unsigned long error, void *context)
{
struct kcopyd_job *job = (struct kcopyd_job *) context;
struct dm_kcopyd_client *kc = job->kc;
if (error) {
if (job->rw == WRITE)
job->write_err |= error;
else
job->read_err = 1;
if (!test_bit(DM_KCOPYD_IGNORE_ERROR, &job->flags)) {
push(&kc->complete_jobs, job);
wake(kc);
return;
}
}
if (job->rw == WRITE)
push(&kc->complete_jobs, job);
else {
job->rw = WRITE;
push(&kc->io_jobs, job);
}
wake(kc);
}
/*
* 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;
struct dm_io_request io_req = {
.bi_rw = job->rw,
.mem.type = DM_IO_PAGE_LIST,
.mem.ptr.pl = job->pages,
.mem.offset = 0,
.notify.fn = complete_io,
.notify.context = job,
.client = job->kc->io_client,
};
if (job->rw == READ)
r = dm_io(&io_req, 1, &job->source, NULL);
else
r = dm_io(&io_req, job->num_dests, job->dests, NULL);
return r;
}
static int run_pages_job(struct kcopyd_job *job)
{
int r;
unsigned nr_pages = dm_div_up(job->dests[0].count, PAGE_SIZE >> 9);
r = kcopyd_get_pages(job->kc, nr_pages, &job->pages);
if (!r) {
/* this job is ready for io */
push(&job->kc->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, struct dm_kcopyd_client *kc,
int (*fn) (struct kcopyd_job *))
{
struct kcopyd_job *job;
int r, count = 0;
while ((job = pop(jobs, kc))) {
r = fn(job);
if (r < 0) {
/* error this rogue job */
if (job->rw == WRITE)
job->write_err = (unsigned long) -1L;
else
job->read_err = 1;
push(&kc->complete_jobs, job);
break;
}
if (r > 0) {
/*
* We couldn't service this job ATM, so
* push this job back onto the list.
*/
push_head(jobs, job);
break;
}
count++;
}
return count;
}
/*
* kcopyd does this every time it's woken up.
*/
static void do_work(struct work_struct *work)
{
struct dm_kcopyd_client *kc = container_of(work,
struct dm_kcopyd_client, kcopyd_work);
struct blk_plug plug;
/*
* 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.
*/
blk_start_plug(&plug);
process_jobs(&kc->complete_jobs, kc, run_complete_job);
process_jobs(&kc->pages_jobs, kc, run_pages_job);
process_jobs(&kc->io_jobs, kc, run_io_job);
blk_finish_plug(&plug);
}
/*
* 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)
{
struct dm_kcopyd_client *kc = job->kc;
atomic_inc(&kc->nr_jobs);
if (unlikely(!job->source.count))
push(&kc->complete_jobs, job);
else if (job->pages == &zero_page_list)
push(&kc->io_jobs, job);
else
push(&kc->pages_jobs, job);
wake(kc);
}
static void segment_complete(int read_err, unsigned long write_err,
void *context)
{
/* FIXME: tidy this function */
sector_t progress = 0;
sector_t count = 0;
struct kcopyd_job *sub_job = (struct kcopyd_job *) context;
struct kcopyd_job *job = sub_job->master_job;
struct dm_kcopyd_client *kc = job->kc;
mutex_lock(&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(DM_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;
}
}
mutex_unlock(&job->lock);
if (count) {
int i;
*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 = sub_job;
dispatch_job(sub_job);
} else if (atomic_dec_and_test(&job->sub_jobs)) {
/*
* Queue the completion callback to the kcopyd thread.
*
* Some callers assume that all the completions are called
* from a single thread and don't race with each other.
*
* We must not call the callback directly here because this
* code may not be executing in the thread.
*/
push(&kc->complete_jobs, job);
wake(kc);
}
}
/*
* Create some sub jobs to share the work between them.
*/
static void split_job(struct kcopyd_job *master_job)
{
int i;
atomic_inc(&master_job->kc->nr_jobs);
atomic_set(&master_job->sub_jobs, SPLIT_COUNT);
for (i = 0; i < SPLIT_COUNT; i++) {
master_job[i + 1].master_job = master_job;
segment_complete(0, 0u, &master_job[i + 1]);
}
}
int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
unsigned int num_dests, struct dm_io_region *dests,
unsigned int flags, dm_kcopyd_notify_fn fn, void *context)
{
struct kcopyd_job *job;
/*
* Allocate an array of jobs consisting of one master job
* followed by SPLIT_COUNT sub jobs.
*/
job = mempool_alloc(kc->job_pool, GFP_NOIO);
/*
* set up for the read.
*/
job->kc = kc;
job->flags = flags;
job->read_err = 0;
job->write_err = 0;
job->num_dests = num_dests;
memcpy(&job->dests, dests, sizeof(*dests) * num_dests);
if (from) {
job->source = *from;
job->pages = NULL;
job->rw = READ;
} else {
memset(&job->source, 0, sizeof job->source);
job->source.count = job->dests[0].count;
job->pages = &zero_page_list;
job->rw = WRITE;
}
job->fn = fn;
job->context = context;
job->master_job = job;
if (job->source.count <= SUB_JOB_SIZE)
dispatch_job(job);
else {
mutex_init(&job->lock);
job->progress = 0;
split_job(job);
}
return 0;
}
EXPORT_SYMBOL(dm_kcopyd_copy);
int dm_kcopyd_zero(struct dm_kcopyd_client *kc,
unsigned num_dests, struct dm_io_region *dests,
unsigned flags, dm_kcopyd_notify_fn fn, void *context)
{
return dm_kcopyd_copy(kc, NULL, num_dests, dests, flags, fn, context);
}
EXPORT_SYMBOL(dm_kcopyd_zero);
void *dm_kcopyd_prepare_callback(struct dm_kcopyd_client *kc,
dm_kcopyd_notify_fn fn, void *context)
{
struct kcopyd_job *job;
job = mempool_alloc(kc->job_pool, GFP_NOIO);
memset(job, 0, sizeof(struct kcopyd_job));
job->kc = kc;
job->fn = fn;
job->context = context;
job->master_job = job;
atomic_inc(&kc->nr_jobs);
return job;
}
EXPORT_SYMBOL(dm_kcopyd_prepare_callback);
void dm_kcopyd_do_callback(void *j, int read_err, unsigned long write_err)
{
struct kcopyd_job *job = j;
struct dm_kcopyd_client *kc = job->kc;
job->read_err = read_err;
job->write_err = write_err;
push(&kc->complete_jobs, job);
wake(kc);
}
EXPORT_SYMBOL(dm_kcopyd_do_callback);
/*
* Cancels a kcopyd job, eg. someone might be deactivating a
* mirror.
*/
#if 0
int kcopyd_cancel(struct kcopyd_job *job, int block)
{
/* FIXME: finish */
return -1;
}
#endif /* 0 */
/*-----------------------------------------------------------------
* Client setup
*---------------------------------------------------------------*/
struct dm_kcopyd_client *dm_kcopyd_client_create(void)
{
int r = -ENOMEM;
struct dm_kcopyd_client *kc;
kc = kmalloc(sizeof(*kc), GFP_KERNEL);
if (!kc)
return ERR_PTR(-ENOMEM);
spin_lock_init(&kc->job_lock);
INIT_LIST_HEAD(&kc->complete_jobs);
INIT_LIST_HEAD(&kc->io_jobs);
INIT_LIST_HEAD(&kc->pages_jobs);
kc->job_pool = mempool_create_slab_pool(MIN_JOBS, _job_cache);
if (!kc->job_pool)
goto bad_slab;
INIT_WORK(&kc->kcopyd_work, do_work);
kc->kcopyd_wq = alloc_workqueue("kcopyd",
WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
if (!kc->kcopyd_wq)
goto bad_workqueue;
kc->pages = NULL;
kc->nr_reserved_pages = kc->nr_free_pages = 0;
r = client_reserve_pages(kc, RESERVE_PAGES);
if (r)
goto bad_client_pages;
kc->io_client = dm_io_client_create();
if (IS_ERR(kc->io_client)) {
r = PTR_ERR(kc->io_client);
goto bad_io_client;
}
init_waitqueue_head(&kc->destroyq);
atomic_set(&kc->nr_jobs, 0);
return kc;
bad_io_client:
client_free_pages(kc);
bad_client_pages:
destroy_workqueue(kc->kcopyd_wq);
bad_workqueue:
mempool_destroy(kc->job_pool);
bad_slab:
kfree(kc);
return ERR_PTR(r);
}
EXPORT_SYMBOL(dm_kcopyd_client_create);
void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc)
{
/* Wait for completion of all jobs submitted by this client. */
wait_event(kc->destroyq, !atomic_read(&kc->nr_jobs));
BUG_ON(!list_empty(&kc->complete_jobs));
BUG_ON(!list_empty(&kc->io_jobs));
BUG_ON(!list_empty(&kc->pages_jobs));
destroy_workqueue(kc->kcopyd_wq);
dm_io_client_destroy(kc->io_client);
client_free_pages(kc);
mempool_destroy(kc->job_pool);
kfree(kc);
}
EXPORT_SYMBOL(dm_kcopyd_client_destroy);