Commit 099c81a1 authored by John Groves's avatar John Groves Committed by Ira Weiny
Browse files

dax: Add dax_operations for use by fs-dax on fsdev dax 



fsdev: Add dax_operations for use by famfs.

This replicates the functionality from drivers/nvdimm/pmem.c that
conventional fs-dax file systems (e.g. xfs) use to support dax
read/write/mmap to a daxdev - without which famfs can't sit atop a
daxdev.

- These methods are based on pmem_dax_ops from drivers/nvdimm/pmem.c
- fsdev_dax_direct_access() returns the hpa, pfn and kva. The kva was
  newly stored as dev_dax->virt_addr by dev_dax_probe().
- The hpa/pfn are used for mmap (dax_iomap_fault()), and the kva is used
  for read/write (dax_iomap_rw())
- fsdev_dax_recovery_write() and dev_dax_zero_page_range() have not been
  tested yet. I'm looking for suggestions as to how to test those.
- dax-private.h: add dev_dax->cached_size, which fsdev needs to
  remember. The dev_dax size cannot change while a driver is bound
  (dev_dax_resize returns -EBUSY if dev->driver is set). Caching the size
  at probe time allows fsdev's direct_access path can use it without
  acquiring dax_dev_rwsem (which isn't exported anyway).

Signed-off-by: default avatarJohn Groves <john@groves.net>
Link: https://patch.msgid.link/0100019d311d415a-bd6af0fe-5445-484c-9d39-210b8170b686-000000@email.amazonses.com


Signed-off-by: default avatarIra Weiny <ira.weiny@intel.com>
parent 75945584

drivers/dax/dax-private.h

+2 −0
Original line number Diff line number Diff line
@@ -70,6 +70,7 @@ struct dev_dax_range { 
 * @region: parent region

 * @dax_dev: core dax functionality

 * @virt_addr: kva from memremap; used by fsdev_dax

 * @cached_size: size of daxdev cached by fsdev_dax

 * @align: alignment of this instance

 * @target_node: effective numa node if dev_dax memory range is onlined

 * @dyn_id: is this a dynamic or statically created instance
@@ -85,6 +86,7 @@ struct dev_dax { 
	struct dax_region *region;

	struct dax_device *dax_dev;

	void *virt_addr;

	u64 cached_size;

	unsigned int align;

	int target_node;

	bool dyn_id;

drivers/dax/fsdev.c

+84 −0
Original line number Diff line number Diff line
@@ -28,6 +28,85 @@ 
 * - No mmap support - all access is through fs-dax/iomap

 */



static void fsdev_write_dax(void *addr, struct page *page,

		unsigned int off, unsigned int len)

{

	while (len) {

		void *mem = kmap_local_page(page);

		unsigned int chunk = min_t(unsigned int, len, PAGE_SIZE - off);



		memcpy_flushcache(addr, mem + off, chunk);

		kunmap_local(mem);

		len -= chunk;

		off = 0;

		page++;

		addr += chunk;

	}

}



static long __fsdev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,

			long nr_pages, enum dax_access_mode mode, void **kaddr,

			unsigned long *pfn)

{

	struct dev_dax *dev_dax = dax_get_private(dax_dev);

	size_t size = nr_pages << PAGE_SHIFT;

	size_t offset = pgoff << PAGE_SHIFT;

	void *virt_addr = dev_dax->virt_addr + offset;

	phys_addr_t phys;

	unsigned long local_pfn;



	phys = dax_pgoff_to_phys(dev_dax, pgoff, size);

	if (phys == -1) {

		dev_dbg(&dev_dax->dev,

			"pgoff (%#lx) out of range\n", pgoff);

		return -EFAULT;

	}



	if (kaddr)

		*kaddr = virt_addr;



	local_pfn = PHYS_PFN(phys);

	if (pfn)

		*pfn = local_pfn;



	/*

	 * Use cached_size which was computed at probe time. The size cannot

	 * change while the driver is bound (resize returns -EBUSY).

	 */

	return PHYS_PFN(min(size, dev_dax->cached_size - offset));

}



static int fsdev_dax_zero_page_range(struct dax_device *dax_dev,

			pgoff_t pgoff, size_t nr_pages)

{

	void *kaddr;



	WARN_ONCE(nr_pages > 1, "%s: nr_pages > 1\n", __func__);

	__fsdev_dax_direct_access(dax_dev, pgoff, 1, DAX_ACCESS, &kaddr, NULL);

	fsdev_write_dax(kaddr, ZERO_PAGE(0), 0, PAGE_SIZE);

	return 0;

}



static long fsdev_dax_direct_access(struct dax_device *dax_dev,

		  pgoff_t pgoff, long nr_pages, enum dax_access_mode mode,

		  void **kaddr, unsigned long *pfn)

{

	return __fsdev_dax_direct_access(dax_dev, pgoff, nr_pages, mode,

					 kaddr, pfn);

}



static size_t fsdev_dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,

		void *addr, size_t bytes, struct iov_iter *i)

{

	return _copy_from_iter_flushcache(addr, bytes, i);

}



static const struct dax_operations dev_dax_ops = {

	.direct_access = fsdev_dax_direct_access,

	.zero_page_range = fsdev_dax_zero_page_range,

	.recovery_write = fsdev_dax_recovery_write,

};



static void fsdev_cdev_del(void *cdev)

{

	cdev_del(cdev);
@@ -167,6 +246,11 @@ static int fsdev_dax_probe(struct dev_dax *dev_dax) 
		}

	}



	/* Cache size now; it cannot change while driver is bound */

	dev_dax->cached_size = 0;

	for (i = 0; i < dev_dax->nr_range; i++)

		dev_dax->cached_size += range_len(&dev_dax->ranges[i].range);



	/*

	 * Use MEMORY_DEVICE_FS_DAX without setting vmemmap_shift, leaving

	 * folios at order-0. Unlike device.c (MEMORY_DEVICE_GENERIC), this