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Subject[PATCH] 2/5: Device-mapper: kcopyd
kcopyd

--- diff/drivers/md/Makefile 2004-06-01 19:08:00.000000000 -0500
+++ source/drivers/md/Makefile 2004-06-01 19:51:31.000000000 -0500
@@ -3,7 +3,7 @@
#

dm-mod-objs := dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
- dm-ioctl.o dm-io.o
+ dm-ioctl.o dm-io.o kcopyd.o
raid6-objs := raid6main.o raid6algos.o raid6recov.o raid6tables.o \
raid6int1.o raid6int2.o raid6int4.o \
raid6int8.o raid6int16.o raid6int32.o \
--- diff/drivers/md/dm.c 2004-06-01 15:27:33.000000000 -0500
+++ source/drivers/md/dm.c 2004-06-01 19:51:31.000000000 -0500
@@ -153,6 +153,7 @@
xx(dm_target)
xx(dm_linear)
xx(dm_stripe)
+ xx(kcopyd)
xx(dm_interface)
#undef xx
};
--- diff/drivers/md/dm.h 2004-06-01 15:27:33.000000000 -0500
+++ source/drivers/md/dm.h 2004-06-01 19:51:31.000000000 -0500
@@ -177,6 +177,9 @@
int dm_stripe_init(void);
void dm_stripe_exit(void);

+int kcopyd_init(void);
+void kcopyd_exit(void);
+
void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size);

#endif
--- diff/drivers/md/kcopyd.c 1969-12-31 18:00:00.000000000 -0600
+++ source/drivers/md/kcopyd.c 2004-06-01 19:51:31.000000000 -0500
@@ -0,0 +1,667 @@
+/*
+ * Copyright (C) 2002 Sistina Software (UK) Limited.
+ *
+ * This file is released under the GPL.
+ */
+
+#include <asm/atomic.h>
+
+#include <linux/blkdev.h>
+#include <linux/config.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+
+#include "kcopyd.h"
+
+/* FIXME: this is only needed for the DMERR macros */
+#include "dm.h"
+
+static struct workqueue_struct *_kcopyd_wq;
+static struct work_struct _kcopyd_work;
+
+static inline void wake(void)
+{
+ queue_work(_kcopyd_wq, &_kcopyd_work);
+}
+
+/*-----------------------------------------------------------------
+ * Each kcopyd client has its own little pool of preallocated
+ * pages for kcopyd io.
+ *---------------------------------------------------------------*/
+struct kcopyd_client {
+ struct list_head list;
+
+ spinlock_t lock;
+ struct page_list *pages;
+ unsigned int nr_pages;
+ unsigned int nr_free_pages;
+};
+
+static struct page_list *alloc_pl(void)
+{
+ struct page_list *pl;
+
+ pl = kmalloc(sizeof(*pl), GFP_KERNEL);
+ if (!pl)
+ return NULL;
+
+ pl->page = alloc_page(GFP_KERNEL);
+ if (!pl->page) {
+ kfree(pl);
+ return NULL;
+ }
+
+ SetPageLocked(pl->page);
+ return pl;
+}
+
+static void free_pl(struct page_list *pl)
+{
+ ClearPageLocked(pl->page);
+ __free_page(pl->page);
+ kfree(pl);
+}
+
+static int kcopyd_get_pages(struct kcopyd_client *kc,
+ unsigned int nr, struct page_list **pages)
+{
+ struct page_list *pl;
+
+ spin_lock(&kc->lock);
+ if (kc->nr_free_pages < nr) {
+ spin_unlock(&kc->lock);
+ return -ENOMEM;
+ }
+
+ kc->nr_free_pages -= nr;
+ for (*pages = pl = kc->pages; --nr; pl = pl->next)
+ ;
+
+ kc->pages = pl->next;
+ pl->next = 0;
+
+ spin_unlock(&kc->lock);
+
+ return 0;
+}
+
+static void kcopyd_put_pages(struct kcopyd_client *kc, struct page_list *pl)
+{
+ struct page_list *cursor;
+
+ spin_lock(&kc->lock);
+ for (cursor = pl; cursor->next; cursor = cursor->next)
+ kc->nr_free_pages++;
+
+ kc->nr_free_pages++;
+ cursor->next = kc->pages;
+ kc->pages = pl;
+ spin_unlock(&kc->lock);
+}
+
+/*
+ * These three functions resize the page pool.
+ */
+static void drop_pages(struct page_list *pl)
+{
+ struct page_list *next;
+
+ while (pl) {
+ next = pl->next;
+ free_pl(pl);
+ pl = next;
+ }
+}
+
+static int client_alloc_pages(struct kcopyd_client *kc, unsigned int nr)
+{
+ unsigned int i;
+ struct page_list *pl = NULL, *next;
+
+ for (i = 0; i < nr; i++) {
+ next = alloc_pl();
+ if (!next) {
+ if (pl)
+ drop_pages(pl);
+ return -ENOMEM;
+ }
+ next->next = pl;
+ pl = next;
+ }
+
+ kcopyd_put_pages(kc, pl);
+ kc->nr_pages += nr;
+ return 0;
+}
+
+static void client_free_pages(struct kcopyd_client *kc)
+{
+ BUG_ON(kc->nr_free_pages != kc->nr_pages);
+ drop_pages(kc->pages);
+ kc->pages = NULL;
+ kc->nr_free_pages = kc->nr_pages = 0;
+}
+
+/*-----------------------------------------------------------------
+ * kcopyd_jobs need to be allocated by the *clients* of kcopyd,
+ * for this reason we use a mempool to prevent the client from
+ * ever having to do io (which could cause a deadlock).
+ *---------------------------------------------------------------*/
+struct kcopyd_job {
+ struct kcopyd_client *kc;
+ struct list_head list;
+ unsigned long flags;
+
+ /*
+ * Error state of the job.
+ */
+ int read_err;
+ unsigned int write_err;
+
+ /*
+ * Either READ or WRITE
+ */
+ int rw;
+ struct io_region source;
+
+ /*
+ * The destinations for the transfer.
+ */
+ unsigned int num_dests;
+ struct io_region dests[KCOPYD_MAX_REGIONS];
+
+ sector_t offset;
+ unsigned int nr_pages;
+ struct page_list *pages;
+
+ /*
+ * Set this to ensure you are notified when the job has
+ * completed. 'context' is for callback to use.
+ */
+ kcopyd_notify_fn fn;
+ void *context;
+
+ /*
+ * These fields are only used if the job has been split
+ * into more manageable parts.
+ */
+ struct semaphore lock;
+ atomic_t sub_jobs;
+ sector_t progress;
+};
+
+/* FIXME: this should scale with the number of pages */
+#define MIN_JOBS 512
+
+static kmem_cache_t *_job_cache;
+static mempool_t *_job_pool;
+
+/*
+ * We maintain three lists of jobs:
+ *
+ * i) jobs waiting for pages
+ * ii) jobs that have pages, and are waiting for the io to be issued.
+ * iii) jobs that have completed.
+ *
+ * All three of these are protected by job_lock.
+ */
+static spinlock_t _job_lock = SPIN_LOCK_UNLOCKED;
+
+static LIST_HEAD(_complete_jobs);
+static LIST_HEAD(_io_jobs);
+static LIST_HEAD(_pages_jobs);
+
+static int __init jobs_init(void)
+{
+ INIT_LIST_HEAD(&_complete_jobs);
+ INIT_LIST_HEAD(&_io_jobs);
+ INIT_LIST_HEAD(&_pages_jobs);
+
+ _job_cache = kmem_cache_create("kcopyd-jobs",
+ sizeof(struct kcopyd_job),
+ __alignof__(struct kcopyd_job),
+ 0, NULL, NULL);
+ if (!_job_cache)
+ return -ENOMEM;
+
+ _job_pool = mempool_create(MIN_JOBS, mempool_alloc_slab,
+ mempool_free_slab, _job_cache);
+ if (!_job_pool) {
+ kmem_cache_destroy(_job_cache);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void jobs_exit(void)
+{
+ BUG_ON(!list_empty(&_complete_jobs));
+ BUG_ON(!list_empty(&_io_jobs));
+ BUG_ON(!list_empty(&_pages_jobs));
+
+ mempool_destroy(_job_pool);
+ kmem_cache_destroy(_job_cache);
+}
+
+/*
+ * Functions to push and pop a job onto the head of a given job
+ * list.
+ */
+static inline struct kcopyd_job *pop(struct list_head *jobs)
+{
+ struct kcopyd_job *job = NULL;
+ unsigned long flags;
+
+ spin_lock_irqsave(&_job_lock, flags);
+
+ if (!list_empty(jobs)) {
+ job = list_entry(jobs->next, struct kcopyd_job, list);
+ list_del(&job->list);
+ }
+ spin_unlock_irqrestore(&_job_lock, flags);
+
+ return job;
+}
+
+static inline void push(struct list_head *jobs, struct kcopyd_job *job)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&_job_lock, flags);
+ list_add_tail(&job->list, jobs);
+ spin_unlock_irqrestore(&_job_lock, flags);
+}
+
+/*
+ * These three functions process 1 item from the corresponding
+ * job list.
+ *
+ * They return:
+ * < 0: error
+ * 0: success
+ * > 0: can't process yet.
+ */
+static int run_complete_job(struct kcopyd_job *job)
+{
+ void *context = job->context;
+ int read_err = job->read_err;
+ unsigned int write_err = job->write_err;
+ kcopyd_notify_fn fn = job->fn;
+
+ kcopyd_put_pages(job->kc, job->pages);
+ mempool_free(job, _job_pool);
+ fn(read_err, write_err, context);
+ return 0;
+}
+
+static void complete_io(unsigned long error, void *context)
+{
+ struct kcopyd_job *job = (struct kcopyd_job *) context;
+
+ if (error) {
+ if (job->rw == WRITE)
+ job->write_err &= error;
+ else
+ job->read_err = 1;
+
+ if (!test_bit(KCOPYD_IGNORE_ERROR, &job->flags)) {
+ push(&_complete_jobs, job);
+ wake();
+ return;
+ }
+ }
+
+ if (job->rw == WRITE)
+ push(&_complete_jobs, job);
+
+ else {
+ job->rw = WRITE;
+ push(&_io_jobs, job);
+ }
+
+ wake();
+}
+
+/*
+ * Request io on as many buffer heads as we can currently get for
+ * a particular job.
+ */
+static int run_io_job(struct kcopyd_job *job)
+{
+ int r;
+
+ if (job->rw == READ)
+ r = dm_io_async(1, &job->source, job->rw,
+ job->pages,
+ job->offset, complete_io, job);
+
+ else
+ r = dm_io_async(job->num_dests, job->dests, job->rw,
+ job->pages,
+ job->offset, complete_io, job);
+
+ return r;
+}
+
+static int run_pages_job(struct kcopyd_job *job)
+{
+ int r;
+
+ job->nr_pages = dm_div_up(job->dests[0].count + job->offset,
+ PAGE_SIZE >> 9);
+ r = kcopyd_get_pages(job->kc, job->nr_pages, &job->pages);
+ if (!r) {
+ /* this job is ready for io */
+ push(&_io_jobs, job);
+ return 0;
+ }
+
+ if (r == -ENOMEM)
+ /* can't complete now */
+ return 1;
+
+ return r;
+}
+
+/*
+ * Run through a list for as long as possible. Returns the count
+ * of successful jobs.
+ */
+static int process_jobs(struct list_head *jobs, int (*fn) (struct kcopyd_job *))
+{
+ struct kcopyd_job *job;
+ int r, count = 0;
+
+ while ((job = pop(jobs))) {
+
+ r = fn(job);
+
+ if (r < 0) {
+ /* error this rogue job */
+ if (job->rw == WRITE)
+ job->write_err = (unsigned int) -1;
+ else
+ job->read_err = 1;
+ push(&_complete_jobs, job);
+ break;
+ }
+
+ if (r > 0) {
+ /*
+ * We couldn't service this job ATM, so
+ * push this job back onto the list.
+ */
+ push(jobs, job);
+ break;
+ }
+
+ count++;
+ }
+
+ return count;
+}
+
+/*
+ * kcopyd does this every time it's woken up.
+ */
+static void do_work(void *ignored)
+{
+ /*
+ * The order that these are called is *very* important.
+ * complete jobs can free some pages for pages jobs.
+ * Pages jobs when successful will jump onto the io jobs
+ * list. io jobs call wake when they complete and it all
+ * starts again.
+ */
+ process_jobs(&_complete_jobs, run_complete_job);
+ process_jobs(&_pages_jobs, run_pages_job);
+ process_jobs(&_io_jobs, run_io_job);
+}
+
+/*
+ * If we are copying a small region we just dispatch a single job
+ * to do the copy, otherwise the io has to be split up into many
+ * jobs.
+ */
+static void dispatch_job(struct kcopyd_job *job)
+{
+ push(&_pages_jobs, job);
+ wake();
+}
+
+#define SUB_JOB_SIZE 128
+static void segment_complete(int read_err,
+ unsigned int write_err, void *context)
+{
+ /* FIXME: tidy this function */
+ sector_t progress = 0;
+ sector_t count = 0;
+ struct kcopyd_job *job = (struct kcopyd_job *) context;
+
+ down(&job->lock);
+
+ /* update the error */
+ if (read_err)
+ job->read_err = 1;
+
+ if (write_err)
+ job->write_err &= write_err;
+
+ /*
+ * Only dispatch more work if there hasn't been an error.
+ */
+ if ((!job->read_err && !job->write_err) ||
+ test_bit(KCOPYD_IGNORE_ERROR, &job->flags)) {
+ /* get the next chunk of work */
+ progress = job->progress;
+ count = job->source.count - progress;
+ if (count) {
+ if (count > SUB_JOB_SIZE)
+ count = SUB_JOB_SIZE;
+
+ job->progress += count;
+ }
+ }
+ up(&job->lock);
+
+ if (count) {
+ int i;
+ struct kcopyd_job *sub_job = mempool_alloc(_job_pool, GFP_NOIO);
+
+ memcpy(sub_job, job, sizeof(*job));
+ sub_job->source.sector += progress;
+ sub_job->source.count = count;
+
+ for (i = 0; i < job->num_dests; i++) {
+ sub_job->dests[i].sector += progress;
+ sub_job->dests[i].count = count;
+ }
+
+ sub_job->fn = segment_complete;
+ sub_job->context = job;
+ dispatch_job(sub_job);
+
+ } else if (atomic_dec_and_test(&job->sub_jobs)) {
+
+ /*
+ * To avoid a race we must keep the job around
+ * until after the notify function has completed.
+ * Otherwise the client may try and stop the job
+ * after we've completed.
+ */
+ job->fn(read_err, write_err, job->context);
+ mempool_free(job, _job_pool);
+ }
+}
+
+/*
+ * Create some little jobs that will do the move between
+ * them.
+ */
+#define SPLIT_COUNT 8
+static void split_job(struct kcopyd_job *job)
+{
+ int i;
+
+ atomic_set(&job->sub_jobs, SPLIT_COUNT);
+ for (i = 0; i < SPLIT_COUNT; i++)
+ segment_complete(0, 0u, job);
+}
+
+int kcopyd_copy(struct kcopyd_client *kc, struct io_region *from,
+ unsigned int num_dests, struct io_region *dests,
+ unsigned int flags, kcopyd_notify_fn fn, void *context)
+{
+ struct kcopyd_job *job;
+
+ /*
+ * Allocate a new job.
+ */
+ job = mempool_alloc(_job_pool, GFP_NOIO);
+
+ /*
+ * set up for the read.
+ */
+ job->kc = kc;
+ job->flags = flags;
+ job->read_err = 0;
+ job->write_err = 0;
+ job->rw = READ;
+
+ memcpy(&job->source, from, sizeof(*from));
+
+ job->num_dests = num_dests;
+ memcpy(&job->dests, dests, sizeof(*dests) * num_dests);
+
+ job->offset = 0;
+ job->nr_pages = 0;
+ job->pages = NULL;
+
+ job->fn = fn;
+ job->context = context;
+
+ if (job->source.count < SUB_JOB_SIZE)
+ dispatch_job(job);
+
+ else {
+ init_MUTEX(&job->lock);
+ job->progress = 0;
+ split_job(job);
+ }
+
+ return 0;
+}
+
+/*
+ * Cancels a kcopyd job, eg. someone might be deactivating a
+ * mirror.
+ */
+int kcopyd_cancel(struct kcopyd_job *job, int block)
+{
+ /* FIXME: finish */
+ return -1;
+}
+
+/*-----------------------------------------------------------------
+ * Unit setup
+ *---------------------------------------------------------------*/
+static DECLARE_MUTEX(_client_lock);
+static LIST_HEAD(_clients);
+
+static int client_add(struct kcopyd_client *kc)
+{
+ down(&_client_lock);
+ list_add(&kc->list, &_clients);
+ up(&_client_lock);
+ return 0;
+}
+
+static void client_del(struct kcopyd_client *kc)
+{
+ down(&_client_lock);
+ list_del(&kc->list);
+ up(&_client_lock);
+}
+
+int kcopyd_client_create(unsigned int nr_pages, struct kcopyd_client **result)
+{
+ int r = 0;
+ struct kcopyd_client *kc;
+
+ kc = kmalloc(sizeof(*kc), GFP_KERNEL);
+ if (!kc)
+ return -ENOMEM;
+
+ kc->lock = SPIN_LOCK_UNLOCKED;
+ kc->pages = NULL;
+ kc->nr_pages = kc->nr_free_pages = 0;
+ r = client_alloc_pages(kc, nr_pages);
+ if (r) {
+ kfree(kc);
+ return r;
+ }
+
+ r = dm_io_get(nr_pages);
+ if (r) {
+ client_free_pages(kc);
+ kfree(kc);
+ return r;
+ }
+
+ r = client_add(kc);
+ if (r) {
+ dm_io_put(nr_pages);
+ client_free_pages(kc);
+ kfree(kc);
+ return r;
+ }
+
+ *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);
+}
+
+
+int __init kcopyd_init(void)
+{
+ int r;
+
+ r = jobs_init();
+ if (r)
+ return r;
+
+ _kcopyd_wq = create_singlethread_workqueue("kcopyd");
+ if (!_kcopyd_wq) {
+ jobs_exit();
+ return -ENOMEM;
+ }
+
+ INIT_WORK(&_kcopyd_work, do_work, NULL);
+ return 0;
+}
+
+void kcopyd_exit(void)
+{
+ jobs_exit();
+ destroy_workqueue(_kcopyd_wq);
+}
+
+EXPORT_SYMBOL(kcopyd_client_create);
+EXPORT_SYMBOL(kcopyd_client_destroy);
+EXPORT_SYMBOL(kcopyd_copy);
+EXPORT_SYMBOL(kcopyd_cancel);
--- diff/drivers/md/kcopyd.h 1969-12-31 18:00:00.000000000 -0600
+++ source/drivers/md/kcopyd.h 2004-06-01 19:51:31.000000000 -0500
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2001 Sistina Software
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_KCOPYD_H
+#define DM_KCOPYD_H
+
+#include "dm-io.h"
+
+int kcopyd_init(void);
+void kcopyd_exit(void);
+
+/* FIXME: make this configurable */
+#define KCOPYD_MAX_REGIONS 8
+
+#define KCOPYD_IGNORE_ERROR 1
+
+/*
+ * To use kcopyd you must first create a kcopyd client object.
+ */
+struct kcopyd_client;
+int kcopyd_client_create(unsigned int num_pages, struct kcopyd_client **result);
+void kcopyd_client_destroy(struct kcopyd_client *kc);
+
+/*
+ * Submit a copy job to kcopyd. This is built on top of the
+ * previous three fns.
+ *
+ * read_err is a boolean,
+ * write_err is a bitset, with 1 bit for each destination region
+ */
+typedef void (*kcopyd_notify_fn)(int read_err,
+ unsigned int write_err, void *context);
+
+int kcopyd_copy(struct kcopyd_client *kc, struct io_region *from,
+ unsigned int num_dests, struct io_region *dests,
+ unsigned int flags, kcopyd_notify_fn fn, void *context);
+
+#endif
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