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dax: refactor dax-fs into a generic provider of 'struct dax_device' instances

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We want dax capable drivers to be able to publish a set of dax
operations [1]. However, we do not want to further abuse block_devices
to advertise these operations. Instead we will attach these operations
to a dax device and add a lookup mechanism to go from block device path
to a dax device. A dax capable driver like pmem or brd is responsible
for registering a dax device, alongside a block device, and then a dax
capable filesystem is responsible for retrieving the dax device by path
name if it wants to call dax_operations.

For now, we refactor the dax pseudo-fs to be a generic facility, rather
than an implementation detail, of the device-dax use case. Where a "dax
device" is just an inode + dax infrastructure, and "Device DAX" is a
mapping service layered on top of that base 'struct dax_device'.
"Filesystem DAX" is then a mapping service that layers a filesystem on
top of that same base device. Filesystem DAX is associated with a
block_device for now, but perhaps directly to a dax device in the
future, or for new pmem-only filesystems.

[1]: https://lkml.org/lkml/2017/1/19/880

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams
2017-04-11 09:49:49 -07:00
parent 5f0694b300
commit 7b6be8444e
10 changed files with 405 additions and 218 deletions
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20
drivers/dax/dax.h
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@@ -1,5 +1,5 @@
/*
* Copyright(c) 2016 Intel Corporation. All rights reserved.
* Copyright(c) 2016 - 2017 Intel Corporation. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
@@ -12,14 +12,12 @@
*/
#ifndef __DAX_H__
#define __DAX_H__
struct device;
struct dev_dax;
struct resource;
struct dax_region;
void dax_region_put(struct dax_region *dax_region);
struct dax_region *alloc_dax_region(struct device *parent,
int region_id, struct resource *res, unsigned int align,
void *addr, unsigned long flags);
struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
struct resource *res, int count);
struct dax_device;
struct dax_device *alloc_dax(void *private);
void put_dax(struct dax_device *dax_dev);
bool dax_alive(struct dax_device *dax_dev);
void kill_dax(struct dax_device *dax_dev);
struct dax_device *inode_dax(struct inode *inode);
struct inode *dax_inode(struct dax_device *dax_dev);
void *dax_get_private(struct dax_device *dax_dev);
#endif /* __DAX_H__ */