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