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[PATCH] dm snapshot: fix kcopyd destructor

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Before removing a snapshot, wait for the completion of any kcopyd jobs using
it.

Do this by maintaining a count (nr_jobs) of how many outstanding jobs each
kcopyd_client has.

The snapshot destructor first unregisters the snapshot so that no new kcopyd
jobs (created by writes to the origin) will reference that particular
snapshot.  kcopyd_client_destroy() is now run next to wait for the completion
of any outstanding jobs before the snapshot exception structures (that those
jobs reference) are freed.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Alasdair G Kergon 2006-03-27 01:17:50 -08:00 committed by Linus Torvalds
parent 969429b504
commit 138728dc96
2 changed files with 21 additions and 2 deletions
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6
drivers/md/dm-snap.c
View File

@ -559,8 +559,12 @@ static void snapshot_dtr(struct dm_target *ti)
{
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
/* Prevent further origin writes from using this snapshot. */
/* After this returns there can be no new kcopyd jobs. */
unregister_snapshot(s);
kcopyd_client_destroy(s->kcopyd_client);
exit_exception_table(&s->pending, pending_cache);
exit_exception_table(&s->complete, exception_cache);
@ -569,7 +573,7 @@ static void snapshot_dtr(struct dm_target *ti)
dm_put_device(ti, s->origin);
dm_put_device(ti, s->cow);
kcopyd_client_destroy(s->kcopyd_client);
kfree(s);
}

17
drivers/md/kcopyd.c
View File

@ -44,6 +44,9 @@ struct kcopyd_client {
struct page_list *pages;
unsigned int nr_pages;
unsigned int nr_free_pages;
wait_queue_head_t destroyq;
atomic_t nr_jobs;
};
static struct page_list *alloc_pl(void)
@ -292,10 +295,15 @@ static int run_complete_job(struct kcopyd_job *job)
int read_err = job->read_err;
unsigned int write_err = job->write_err;
kcopyd_notify_fn fn = job->fn;
struct kcopyd_client *kc = job->kc;
kcopyd_put_pages(job->kc, job->pages);
kcopyd_put_pages(kc, job->pages);
mempool_free(job, _job_pool);
fn(read_err, write_err, context);
if (atomic_dec_and_test(&kc->nr_jobs))
wake_up(&kc->destroyq);
return 0;
}
@ -430,6 +438,7 @@ static void do_work(void *ignored)
*/
static void dispatch_job(struct kcopyd_job *job)
{
atomic_inc(&job->kc->nr_jobs);
push(&_pages_jobs, job);
wake();
}
@ -669,6 +678,9 @@ int kcopyd_client_create(unsigned int nr_pages, struct kcopyd_client **result)
return r;
}
init_waitqueue_head(&kc->destroyq);
atomic_set(&kc->nr_jobs, 0);
client_add(kc);
*result = kc;
return 0;
@ -676,6 +688,9 @@ int kcopyd_client_create(unsigned int nr_pages, struct kcopyd_client **result)
void kcopyd_client_destroy(struct kcopyd_client *kc)
{
/* Wait for completion of all jobs submitted by this client. */
wait_event(kc->destroyq, !atomic_read(&kc->nr_jobs));
dm_io_put(kc->nr_pages);
client_free_pages(kc);
client_del(kc);