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![Mikulas Patocka](/assets/img/avatar_default.png)
If the thread calling dm_kcopyd_copy is delayed due to scheduling inside split_job/segment_complete and the subjobs complete before the loop in split_job completes, the kcopyd callback could be invoked from the thread that called dm_kcopyd_copy instead of the kcopyd workqueue. dm_kcopyd_copy -> split_job -> segment_complete -> job->fn() Snapshots depend on the fact that callbacks are called from the singlethreaded kcopyd workqueue and expect that there is no racing between individual callbacks. The racing between callbacks can lead to corruption of exception store and it can also mean that exception store callbacks are called twice for the same exception - a likely reason for crashes reported inside pending_complete() / remove_exception(). This patch fixes two problems: 1. job->fn being called from the thread that submitted the job (see above). - Fix: hand over the completion callback to the kcopyd thread. 2. job->fn(read_err, write_err, job->context); in segment_complete reports the error of the last subjob, not the union of all errors. - Fix: pass job->write_err to the callback to report all error bits (it is done already in run_complete_job) Cc: stable@kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
673 lines
14 KiB
C
673 lines
14 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 <asm/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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/*-----------------------------------------------------------------
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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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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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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 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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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 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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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 dm_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 dm_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 dm_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 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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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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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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};
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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 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(kcopyd_job, 0);
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if (!_job_cache)
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return -ENOMEM;
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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)
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kcopyd_put_pages(kc, job->pages);
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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 | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG),
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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 = job->offset,
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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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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(&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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/*
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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(&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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}
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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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push(&kc->pages_jobs, job);
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wake(kc);
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}
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#define SUB_JOB_SIZE 128
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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 *job = (struct kcopyd_job *) context;
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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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struct kcopyd_job *sub_job = mempool_alloc(kc->job_pool,
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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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* 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 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_inc(&job->kc->nr_jobs);
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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 dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
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unsigned int num_dests, struct dm_io_region *dests,
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unsigned int flags, dm_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(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->rw = READ;
|
|
|
|
job->source = *from;
|
|
|
|
job->num_dests = num_dests;
|
|
memcpy(&job->dests, dests, sizeof(*dests) * num_dests);
|
|
|
|
job->offset = 0;
|
|
job->nr_pages = 0;
|
|
job->pages = NULL;
|
|
|
|
job->fn = fn;
|
|
job->context = context;
|
|
|
|
if (job->source.count < SUB_JOB_SIZE)
|
|
dispatch_job(job);
|
|
|
|
else {
|
|
mutex_init(&job->lock);
|
|
job->progress = 0;
|
|
split_job(job);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(dm_kcopyd_copy);
|
|
|
|
/*
|
|
* 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
|
|
*---------------------------------------------------------------*/
|
|
int dm_kcopyd_client_create(unsigned int nr_pages,
|
|
struct dm_kcopyd_client **result)
|
|
{
|
|
int r = -ENOMEM;
|
|
struct dm_kcopyd_client *kc;
|
|
|
|
kc = kmalloc(sizeof(*kc), GFP_KERNEL);
|
|
if (!kc)
|
|
return -ENOMEM;
|
|
|
|
spin_lock_init(&kc->lock);
|
|
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 = create_singlethread_workqueue("kcopyd");
|
|
if (!kc->kcopyd_wq)
|
|
goto bad_workqueue;
|
|
|
|
kc->pages = NULL;
|
|
kc->nr_pages = kc->nr_free_pages = 0;
|
|
r = client_alloc_pages(kc, nr_pages);
|
|
if (r)
|
|
goto bad_client_pages;
|
|
|
|
kc->io_client = dm_io_client_create(nr_pages);
|
|
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);
|
|
|
|
*result = kc;
|
|
return 0;
|
|
|
|
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 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);
|