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7f06965390
This patch introduces dm_kcopyd_zero() to make it easy to use kcopyd to write zeros into the requested areas instead instead of copying. It is implemented by passing a NULL copying source to dm_kcopyd_copy(). The forthcoming thin provisioning target uses this. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
757 lines
16 KiB
C
757 lines
16 KiB
C
/*
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* Copyright (C) 2002 Sistina Software (UK) Limited.
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* Copyright (C) 2006 Red Hat GmbH
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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 <linux/types.h>
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#include <linux/atomic.h>
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#include <linux/blkdev.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 <linux/mutex.h>
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#include <linux/device-mapper.h>
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#include <linux/dm-kcopyd.h>
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#include "dm.h"
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#define SUB_JOB_SIZE 128
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#define SPLIT_COUNT 8
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#define MIN_JOBS 8
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#define RESERVE_PAGES (DIV_ROUND_UP(SUB_JOB_SIZE << SECTOR_SHIFT, PAGE_SIZE))
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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 dm_kcopyd_client {
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struct page_list *pages;
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unsigned nr_reserved_pages;
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unsigned nr_free_pages;
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struct dm_io_client *io_client;
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wait_queue_head_t destroyq;
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atomic_t nr_jobs;
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mempool_t *job_pool;
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struct workqueue_struct *kcopyd_wq;
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struct work_struct kcopyd_work;
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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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spinlock_t job_lock;
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struct list_head complete_jobs;
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struct list_head io_jobs;
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struct list_head pages_jobs;
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};
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static struct page_list zero_page_list;
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static void wake(struct dm_kcopyd_client *kc)
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{
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queue_work(kc->kcopyd_wq, &kc->kcopyd_work);
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}
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/*
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* Obtain one page for the use of kcopyd.
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*/
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static struct page_list *alloc_pl(gfp_t gfp)
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{
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struct page_list *pl;
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pl = kmalloc(sizeof(*pl), gfp);
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if (!pl)
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return NULL;
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pl->page = alloc_page(gfp);
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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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/*
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* Add the provided pages to a client's free page list, releasing
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* back to the system any beyond the reserved_pages limit.
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*/
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static void kcopyd_put_pages(struct dm_kcopyd_client *kc, struct page_list *pl)
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{
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struct page_list *next;
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do {
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next = pl->next;
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if (kc->nr_free_pages >= kc->nr_reserved_pages)
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free_pl(pl);
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else {
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pl->next = kc->pages;
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kc->pages = pl;
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kc->nr_free_pages++;
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}
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pl = next;
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} while (pl);
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}
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static int kcopyd_get_pages(struct dm_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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*pages = NULL;
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do {
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pl = alloc_pl(__GFP_NOWARN | __GFP_NORETRY);
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if (unlikely(!pl)) {
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/* Use reserved pages */
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pl = kc->pages;
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if (unlikely(!pl))
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goto out_of_memory;
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kc->pages = pl->next;
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kc->nr_free_pages--;
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}
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pl->next = *pages;
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*pages = pl;
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} while (--nr);
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return 0;
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out_of_memory:
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if (*pages)
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kcopyd_put_pages(kc, *pages);
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return -ENOMEM;
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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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/*
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* Allocate and reserve nr_pages for the use of a specific client.
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*/
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static int client_reserve_pages(struct dm_kcopyd_client *kc, unsigned nr_pages)
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{
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unsigned i;
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struct page_list *pl = NULL, *next;
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for (i = 0; i < nr_pages; i++) {
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next = alloc_pl(GFP_KERNEL);
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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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kc->nr_reserved_pages += nr_pages;
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kcopyd_put_pages(kc, pl);
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return 0;
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}
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static void client_free_pages(struct dm_kcopyd_client *kc)
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{
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BUG_ON(kc->nr_free_pages != kc->nr_reserved_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_reserved_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 dm_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 long 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 dm_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 dm_io_region dests[DM_KCOPYD_MAX_REGIONS];
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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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dm_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 mutex lock;
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atomic_t sub_jobs;
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sector_t progress;
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struct kcopyd_job *master_job;
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};
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static struct kmem_cache *_job_cache;
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int __init dm_kcopyd_init(void)
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{
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_job_cache = kmem_cache_create("kcopyd_job",
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sizeof(struct kcopyd_job) * (SPLIT_COUNT + 1),
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__alignof__(struct kcopyd_job), 0, NULL);
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if (!_job_cache)
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return -ENOMEM;
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zero_page_list.next = &zero_page_list;
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zero_page_list.page = ZERO_PAGE(0);
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return 0;
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}
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void dm_kcopyd_exit(void)
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{
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kmem_cache_destroy(_job_cache);
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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 struct kcopyd_job *pop(struct list_head *jobs,
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struct dm_kcopyd_client *kc)
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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(&kc->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(&kc->job_lock, flags);
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return job;
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}
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static 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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struct dm_kcopyd_client *kc = job->kc;
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spin_lock_irqsave(&kc->job_lock, flags);
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list_add_tail(&job->list, jobs);
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spin_unlock_irqrestore(&kc->job_lock, flags);
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}
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static void push_head(struct list_head *jobs, struct kcopyd_job *job)
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{
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unsigned long flags;
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struct dm_kcopyd_client *kc = job->kc;
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spin_lock_irqsave(&kc->job_lock, flags);
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list_add(&job->list, jobs);
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spin_unlock_irqrestore(&kc->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 long write_err = job->write_err;
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dm_kcopyd_notify_fn fn = job->fn;
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struct dm_kcopyd_client *kc = job->kc;
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if (job->pages && job->pages != &zero_page_list)
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kcopyd_put_pages(kc, job->pages);
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/*
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* If this is the master job, the sub jobs have already
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* completed so we can free everything.
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*/
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if (job->master_job == job)
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mempool_free(job, kc->job_pool);
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fn(read_err, write_err, context);
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if (atomic_dec_and_test(&kc->nr_jobs))
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wake_up(&kc->destroyq);
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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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struct dm_kcopyd_client *kc = job->kc;
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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(DM_KCOPYD_IGNORE_ERROR, &job->flags)) {
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push(&kc->complete_jobs, job);
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wake(kc);
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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(&kc->complete_jobs, job);
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else {
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job->rw = WRITE;
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push(&kc->io_jobs, job);
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}
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wake(kc);
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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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struct dm_io_request io_req = {
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.bi_rw = job->rw,
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.mem.type = DM_IO_PAGE_LIST,
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.mem.ptr.pl = job->pages,
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.mem.offset = 0,
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.notify.fn = complete_io,
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.notify.context = job,
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.client = job->kc->io_client,
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};
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if (job->rw == READ)
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r = dm_io(&io_req, 1, &job->source, NULL);
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else
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r = dm_io(&io_req, job->num_dests, job->dests, NULL);
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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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unsigned nr_pages = dm_div_up(job->dests[0].count, PAGE_SIZE >> 9);
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r = kcopyd_get_pages(job->kc, 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(&job->kc->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, struct dm_kcopyd_client *kc,
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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, kc))) {
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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 long) -1L;
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else
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job->read_err = 1;
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push(&kc->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_head(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(struct work_struct *work)
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{
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struct dm_kcopyd_client *kc = container_of(work,
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struct dm_kcopyd_client, kcopyd_work);
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struct blk_plug plug;
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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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blk_start_plug(&plug);
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process_jobs(&kc->complete_jobs, kc, run_complete_job);
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process_jobs(&kc->pages_jobs, kc, run_pages_job);
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process_jobs(&kc->io_jobs, kc, run_io_job);
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blk_finish_plug(&plug);
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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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struct dm_kcopyd_client *kc = job->kc;
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atomic_inc(&kc->nr_jobs);
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if (unlikely(!job->source.count))
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push(&kc->complete_jobs, job);
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else if (job->pages == &zero_page_list)
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push(&kc->io_jobs, job);
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else
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push(&kc->pages_jobs, job);
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wake(kc);
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}
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static void segment_complete(int read_err, unsigned long write_err,
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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 *sub_job = (struct kcopyd_job *) context;
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struct kcopyd_job *job = sub_job->master_job;
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struct dm_kcopyd_client *kc = job->kc;
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mutex_lock(&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(DM_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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mutex_unlock(&job->lock);
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if (count) {
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int i;
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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 = sub_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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* Queue the completion callback to the kcopyd thread.
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*
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* Some callers assume that all the completions are called
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* from a single thread and don't race with each other.
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*
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* We must not call the callback directly here because this
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* code may not be executing in the thread.
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*/
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push(&kc->complete_jobs, job);
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wake(kc);
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}
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}
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/*
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* 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);
|