Commit 1570175a authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
Browse files

PCI/P2PDMA: track pgmap references per resource, not globally 

In preparation for fixing a race between devm_memremap_pages_release()
and the final put of a page from the device-page-map, allocate a
percpu-ref per p2pdma resource mapping.

Link: http://lkml.kernel.org/r/155727338646.292046.9922678317501435597.stgit@dwillia2-desk3.amr.corp.intel.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Reviewed-by: default avatarIra Weiny <ira.weiny@intel.com>
Reviewed-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 795ee306

drivers/pci/p2pdma.c

+81 −43
Original line number Diff line number Diff line
@@ -20,12 +20,16 @@ 
#include <linux/seq_buf.h>



struct pci_p2pdma {

	struct percpu_ref devmap_ref;

	struct completion devmap_ref_done;

	struct gen_pool *pool;

	bool p2pmem_published;

};



struct p2pdma_pagemap {

	struct dev_pagemap pgmap;

	struct percpu_ref ref;

	struct completion ref_done;

};



static ssize_t size_show(struct device *dev, struct device_attribute *attr,

			 char *buf)

{
@@ -74,41 +78,45 @@ static const struct attribute_group p2pmem_group = { 
	.name = "p2pmem",

};



static struct p2pdma_pagemap *to_p2p_pgmap(struct percpu_ref *ref)

{

	return container_of(ref, struct p2pdma_pagemap, ref);

}



static void pci_p2pdma_percpu_release(struct percpu_ref *ref)

{

	struct pci_p2pdma *p2p =

		container_of(ref, struct pci_p2pdma, devmap_ref);

	struct p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(ref);



	complete_all(&p2p->devmap_ref_done);

	complete(&p2p_pgmap->ref_done);

}



static void pci_p2pdma_percpu_kill(struct percpu_ref *ref)

{

	/*

	 * pci_p2pdma_add_resource() may be called multiple times

	 * by a driver and may register the percpu_kill devm action multiple

	 * times. We only want the first action to actually kill the

	 * percpu_ref.

	 */

	if (percpu_ref_is_dying(ref))

		return;



	percpu_ref_kill(ref);

}



static void pci_p2pdma_percpu_cleanup(void *ref)

{

	struct p2pdma_pagemap *p2p_pgmap = to_p2p_pgmap(ref);



	wait_for_completion(&p2p_pgmap->ref_done);

	percpu_ref_exit(&p2p_pgmap->ref);

}



static void pci_p2pdma_release(void *data)

{

	struct pci_dev *pdev = data;

	struct pci_p2pdma *p2pdma = pdev->p2pdma;



	if (!pdev->p2pdma)

	if (!p2pdma)

		return;



	wait_for_completion(&pdev->p2pdma->devmap_ref_done);

	percpu_ref_exit(&pdev->p2pdma->devmap_ref);

	/* Flush and disable pci_alloc_p2p_mem() */

	pdev->p2pdma = NULL;

	synchronize_rcu();



	gen_pool_destroy(pdev->p2pdma->pool);

	gen_pool_destroy(p2pdma->pool);

	sysfs_remove_group(&pdev->dev.kobj, &p2pmem_group);

	pdev->p2pdma = NULL;

}



static int pci_p2pdma_setup(struct pci_dev *pdev)
@@ -124,12 +132,6 @@ static int pci_p2pdma_setup(struct pci_dev *pdev) 
	if (!p2p->pool)

		goto out;



	init_completion(&p2p->devmap_ref_done);

	error = percpu_ref_init(&p2p->devmap_ref,

			pci_p2pdma_percpu_release, 0, GFP_KERNEL);

	if (error)

		goto out_pool_destroy;



	error = devm_add_action_or_reset(&pdev->dev, pci_p2pdma_release, pdev);

	if (error)

		goto out_pool_destroy;
@@ -163,6 +165,7 @@ out: 
int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,

			    u64 offset)

{

	struct p2pdma_pagemap *p2p_pgmap;

	struct dev_pagemap *pgmap;

	void *addr;

	int error;
@@ -185,14 +188,32 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, 
			return error;

	}



	pgmap = devm_kzalloc(&pdev->dev, sizeof(*pgmap), GFP_KERNEL);

	if (!pgmap)

	p2p_pgmap = devm_kzalloc(&pdev->dev, sizeof(*p2p_pgmap), GFP_KERNEL);

	if (!p2p_pgmap)

		return -ENOMEM;



	init_completion(&p2p_pgmap->ref_done);

	error = percpu_ref_init(&p2p_pgmap->ref,

			pci_p2pdma_percpu_release, 0, GFP_KERNEL);

	if (error)

		goto pgmap_free;



	/*

	 * FIXME: the percpu_ref_exit needs to be coordinated internal

	 * to devm_memremap_pages_release(). Duplicate the same ordering

	 * as other devm_memremap_pages() users for now.

	 */

	error = devm_add_action(&pdev->dev, pci_p2pdma_percpu_cleanup,

			&p2p_pgmap->ref);

	if (error)

		goto ref_cleanup;



	pgmap = &p2p_pgmap->pgmap;



	pgmap->res.start = pci_resource_start(pdev, bar) + offset;

	pgmap->res.end = pgmap->res.start + size - 1;

	pgmap->res.flags = pci_resource_flags(pdev, bar);

	pgmap->ref = &pdev->p2pdma->devmap_ref;

	pgmap->ref = &p2p_pgmap->ref;

	pgmap->type = MEMORY_DEVICE_PCI_P2PDMA;

	pgmap->pci_p2pdma_bus_offset = pci_bus_address(pdev, bar) -

		pci_resource_start(pdev, bar);
@@ -201,12 +222,13 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, 
	addr = devm_memremap_pages(&pdev->dev, pgmap);

	if (IS_ERR(addr)) {

		error = PTR_ERR(addr);

		goto pgmap_free;

		goto ref_exit;

	}



	error = gen_pool_add_virt(pdev->p2pdma->pool, (unsigned long)addr,

	error = gen_pool_add_owner(pdev->p2pdma->pool, (unsigned long)addr,

			pci_bus_address(pdev, bar) + offset,

			resource_size(&pgmap->res), dev_to_node(&pdev->dev));

			resource_size(&pgmap->res), dev_to_node(&pdev->dev),

			&p2p_pgmap->ref);

	if (error)

		goto pages_free;
@@ -217,8 +239,10 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size, 


pages_free:

	devm_memunmap_pages(&pdev->dev, pgmap);

ref_cleanup:

	percpu_ref_exit(&p2p_pgmap->ref);

pgmap_free:

	devm_kfree(&pdev->dev, pgmap);

	devm_kfree(&pdev->dev, p2p_pgmap);

	return error;

}

EXPORT_SYMBOL_GPL(pci_p2pdma_add_resource);
@@ -587,19 +611,30 @@ EXPORT_SYMBOL_GPL(pci_p2pmem_find_many); 
 */

void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)

{

	void *ret;

	void *ret = NULL;

	struct percpu_ref *ref;



	/*

	 * Pairs with synchronize_rcu() in pci_p2pdma_release() to

	 * ensure pdev->p2pdma is non-NULL for the duration of the

	 * read-lock.

	 */

	rcu_read_lock();

	if (unlikely(!pdev->p2pdma))

		return NULL;



	if (unlikely(!percpu_ref_tryget_live(&pdev->p2pdma->devmap_ref)))

		return NULL;



	ret = (void *)gen_pool_alloc(pdev->p2pdma->pool, size);

		goto out;



	if (unlikely(!ret))

		percpu_ref_put(&pdev->p2pdma->devmap_ref);

	ret = (void *)gen_pool_alloc_owner(pdev->p2pdma->pool, size,

			(void **) &ref);

	if (!ret)

		goto out;



	if (unlikely(!percpu_ref_tryget_live(ref))) {

		gen_pool_free(pdev->p2pdma->pool, (unsigned long) ret, size);

		ret = NULL;

		goto out;

	}

out:

	rcu_read_unlock();

	return ret;

}

EXPORT_SYMBOL_GPL(pci_alloc_p2pmem);
@@ -612,8 +647,11 @@ EXPORT_SYMBOL_GPL(pci_alloc_p2pmem); 
 */

void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)

{

	gen_pool_free(pdev->p2pdma->pool, (uintptr_t)addr, size);

	percpu_ref_put(&pdev->p2pdma->devmap_ref);

	struct percpu_ref *ref;



	gen_pool_free_owner(pdev->p2pdma->pool, (uintptr_t)addr, size,

			(void **) &ref);

	percpu_ref_put(ref);

}

EXPORT_SYMBOL_GPL(pci_free_p2pmem);

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