Commit 138728dc authored by Alasdair G Kergon's avatar Alasdair G Kergon Committed by Linus Torvalds
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[PATCH] dm snapshot: fix kcopyd destructor 



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: default avatarAlasdair G Kergon <agk@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 969429b5

drivers/md/dm-snap.c

+5 −1
Original line number Diff line number Diff line
@@ -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);

}

drivers/md/kcopyd.c

+16 −1
Original line number Diff line number Diff line
@@ -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);

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