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Commit a63b747b authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge git://git.kvack.org/~bcrl/aio-next 

Pull aio ctx->ring_pages migration serialization fix from Ben LaHaise.

* git://git.kvack.org/~bcrl/aio-next:
  aio: v4 ensure access to ctx->ring_pages is correctly serialised for migration
parents 3123bca7 fa8a53c3

fs/aio.c

+67 −53
Original line number Diff line number Diff line
@@ -52,7 +52,8 @@ 
struct aio_ring {

	unsigned	id;	/* kernel internal index number */

	unsigned	nr;	/* number of io_events */

	unsigned	head;

	unsigned	head;	/* Written to by userland or under ring_lock

				 * mutex by aio_read_events_ring(). */

	unsigned	tail;



	unsigned	magic;
@@ -243,6 +244,11 @@ static void aio_free_ring(struct kioctx *ctx) 
{

	int i;



	/* Disconnect the kiotx from the ring file.  This prevents future

	 * accesses to the kioctx from page migration.

	 */

	put_aio_ring_file(ctx);



	for (i = 0; i < ctx->nr_pages; i++) {

		struct page *page;

		pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
@@ -254,8 +260,6 @@ static void aio_free_ring(struct kioctx *ctx) 
		put_page(page);

	}



	put_aio_ring_file(ctx);



	if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {

		kfree(ctx->ring_pages);

		ctx->ring_pages = NULL;
@@ -283,29 +287,38 @@ static int aio_migratepage(struct address_space *mapping, struct page *new, 
{

	struct kioctx *ctx;

	unsigned long flags;

	pgoff_t idx;

	int rc;



	rc = 0;



	/* Make sure the old page hasn't already been changed */

	/* mapping->private_lock here protects against the kioctx teardown.  */

	spin_lock(&mapping->private_lock);

	ctx = mapping->private_data;

	if (ctx) {

		pgoff_t idx;

		spin_lock_irqsave(&ctx->completion_lock, flags);

	if (!ctx) {

		rc = -EINVAL;

		goto out;

	}



	/* The ring_lock mutex.  The prevents aio_read_events() from writing

	 * to the ring's head, and prevents page migration from mucking in

	 * a partially initialized kiotx.

	 */

	if (!mutex_trylock(&ctx->ring_lock)) {

		rc = -EAGAIN;

		goto out;

	}



	idx = old->index;

	if (idx < (pgoff_t)ctx->nr_pages) {

		/* Make sure the old page hasn't already been changed */

		if (ctx->ring_pages[idx] != old)

			rc = -EAGAIN;

	} else

		rc = -EINVAL;

		spin_unlock_irqrestore(&ctx->completion_lock, flags);

	} else

		rc = -EINVAL;

	spin_unlock(&mapping->private_lock);



	if (rc != 0)

		return rc;

		goto out_unlock;



	/* Writeback must be complete */

	BUG_ON(PageWriteback(old));
@@ -314,38 +327,26 @@ static int aio_migratepage(struct address_space *mapping, struct page *new, 
	rc = migrate_page_move_mapping(mapping, new, old, NULL, mode, 1);

	if (rc != MIGRATEPAGE_SUCCESS) {

		put_page(new);

		return rc;

		goto out_unlock;

	}



	/* We can potentially race against kioctx teardown here.  Use the

	 * address_space's private data lock to protect the mapping's

	 * private_data.

	/* Take completion_lock to prevent other writes to the ring buffer

	 * while the old page is copied to the new.  This prevents new

	 * events from being lost.

	 */

	spin_lock(&mapping->private_lock);

	ctx = mapping->private_data;

	if (ctx) {

		pgoff_t idx;

	spin_lock_irqsave(&ctx->completion_lock, flags);

	migrate_page_copy(new, old);

		idx = old->index;

		if (idx < (pgoff_t)ctx->nr_pages) {

			/* And only do the move if things haven't changed */

			if (ctx->ring_pages[idx] == old)

	BUG_ON(ctx->ring_pages[idx] != old);

	ctx->ring_pages[idx] = new;

			else

				rc = -EAGAIN;

		} else

			rc = -EINVAL;

	spin_unlock_irqrestore(&ctx->completion_lock, flags);

	} else

		rc = -EBUSY;

	spin_unlock(&mapping->private_lock);



	if (rc == MIGRATEPAGE_SUCCESS)

	/* The old page is no longer accessible. */

	put_page(old);

	else

		put_page(new);



out_unlock:

	mutex_unlock(&ctx->ring_lock);

out:

	spin_unlock(&mapping->private_lock);

	return rc;

}

#endif
@@ -380,7 +381,7 @@ static int aio_setup_ring(struct kioctx *ctx) 
	file = aio_private_file(ctx, nr_pages);

	if (IS_ERR(file)) {

		ctx->aio_ring_file = NULL;

		return -EAGAIN;

		return -ENOMEM;

	}



	ctx->aio_ring_file = file;
@@ -415,7 +416,7 @@ static int aio_setup_ring(struct kioctx *ctx) 


	if (unlikely(i != nr_pages)) {

		aio_free_ring(ctx);

		return -EAGAIN;

		return -ENOMEM;

	}



	ctx->mmap_size = nr_pages * PAGE_SIZE;
@@ -429,7 +430,7 @@ static int aio_setup_ring(struct kioctx *ctx) 
	if (IS_ERR((void *)ctx->mmap_base)) {

		ctx->mmap_size = 0;

		aio_free_ring(ctx);

		return -EAGAIN;

		return -ENOMEM;

	}



	pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
@@ -556,6 +557,10 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) 
					rcu_read_unlock();

					spin_unlock(&mm->ioctx_lock);



					/* While kioctx setup is in progress,

					 * we are protected from page migration

					 * changes ring_pages by ->ring_lock.

					 */

					ring = kmap_atomic(ctx->ring_pages[0]);

					ring->id = ctx->id;

					kunmap_atomic(ring);
@@ -640,24 +645,28 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) 


	ctx->max_reqs = nr_events;



	if (percpu_ref_init(&ctx->users, free_ioctx_users))

		goto err;



	if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs))

		goto err;



	spin_lock_init(&ctx->ctx_lock);

	spin_lock_init(&ctx->completion_lock);

	mutex_init(&ctx->ring_lock);

	/* Protect against page migration throughout kiotx setup by keeping

	 * the ring_lock mutex held until setup is complete. */

	mutex_lock(&ctx->ring_lock);

	init_waitqueue_head(&ctx->wait);



	INIT_LIST_HEAD(&ctx->active_reqs);



	if (percpu_ref_init(&ctx->users, free_ioctx_users))

		goto err;



	if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs))

		goto err;



	ctx->cpu = alloc_percpu(struct kioctx_cpu);

	if (!ctx->cpu)

		goto err;



	if (aio_setup_ring(ctx) < 0)

	err = aio_setup_ring(ctx);

	if (err < 0)

		goto err;



	atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
@@ -683,6 +692,9 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) 
	if (err)

		goto err_cleanup;



	/* Release the ring_lock mutex now that all setup is complete. */

	mutex_unlock(&ctx->ring_lock);



	pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",

		 ctx, ctx->user_id, mm, ctx->nr_events);

	return ctx;
@@ -692,6 +704,7 @@ err_cleanup: 
err_ctx:

	aio_free_ring(ctx);

err:

	mutex_unlock(&ctx->ring_lock);

	free_percpu(ctx->cpu);

	free_percpu(ctx->reqs.pcpu_count);

	free_percpu(ctx->users.pcpu_count);
@@ -1024,6 +1037,7 @@ static long aio_read_events_ring(struct kioctx *ctx, 


	mutex_lock(&ctx->ring_lock);



	/* Access to ->ring_pages here is protected by ctx->ring_lock. */

	ring = kmap_atomic(ctx->ring_pages[0]);

	head = ring->head;

	tail = ring->tail;