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Commit 7a862fbb authored by Dan Williams's avatar Dan Williams
Browse files

brd: remove dax support 



DAX support in brd is awkward because its backing page frames are
distinct from the ones provided by pmem, dcssblk, or axonram. We need
pfn_t_devmap() entries to fully support DAX, and the limited DAX support
for pfn_t_special() page frames is not interesting for brd when pmem is
already a superset of brd.  Lastly, brd is the only dax capable driver
that may sleep in its ->direct_access() implementation. So it causes a
global burden with no net gain of kernel functionality.

For all these reasons, remove DAX support.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 66a86cc1

drivers/block/Kconfig

+0 −12
Original line number Original line Diff line number Diff line
@@ -297,7 +297,6 @@ config BLK_DEV_SX8 




config BLK_DEV_RAM

config BLK_DEV_RAM

	tristate "RAM block device support"

	tristate "RAM block device support"

	select DAX if BLK_DEV_RAM_DAX

	---help---

	---help---

	  Saying Y here will allow you to use a portion of your RAM memory as

	  Saying Y here will allow you to use a portion of your RAM memory as

	  a block device, so that you can make file systems on it, read and

	  a block device, so that you can make file systems on it, read and
@@ -333,17 +332,6 @@ config BLK_DEV_RAM_SIZE 
	  The default value is 4096 kilobytes. Only change this if you know

	  The default value is 4096 kilobytes. Only change this if you know

	  what you are doing.

	  what you are doing.





config BLK_DEV_RAM_DAX

	bool "Support Direct Access (DAX) to RAM block devices"

	depends on BLK_DEV_RAM && FS_DAX

	default n

	help

	  Support filesystems using DAX to access RAM block devices.  This

	  avoids double-buffering data in the page cache before copying it

	  to the block device.  Answering Y will slightly enlarge the kernel,

	  and will prevent RAM block device backing store memory from being

	  allocated from highmem (only a problem for highmem systems).



config CDROM_PKTCDVD

config CDROM_PKTCDVD

	tristate "Packet writing on CD/DVD media (DEPRECATED)"

	tristate "Packet writing on CD/DVD media (DEPRECATED)"

	depends on !UML

	depends on !UML

drivers/block/brd.c

+0 −65
Original line number Original line Diff line number Diff line
@@ -20,11 +20,6 @@ 
#include <linux/radix-tree.h>

#include <linux/radix-tree.h>

#include <linux/fs.h>

#include <linux/fs.h>

#include <linux/slab.h>

#include <linux/slab.h>

#ifdef CONFIG_BLK_DEV_RAM_DAX

#include <linux/pfn_t.h>

#include <linux/dax.h>

#include <linux/uio.h>

#endif





#include <linux/uaccess.h>

#include <linux/uaccess.h>
@@ -44,9 +39,6 @@ struct brd_device { 




	struct request_queue	*brd_queue;

	struct request_queue	*brd_queue;

	struct gendisk		*brd_disk;

	struct gendisk		*brd_disk;

#ifdef CONFIG_BLK_DEV_RAM_DAX

	struct dax_device	*dax_dev;

#endif

	struct list_head	brd_list;

	struct list_head	brd_list;





	/*

	/*
@@ -112,9 +104,6 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector) 
	 * restriction might be able to be lifted.

	 * restriction might be able to be lifted.

	 */

	 */

	gfp_flags = GFP_NOIO | __GFP_ZERO;

	gfp_flags = GFP_NOIO | __GFP_ZERO;

#ifndef CONFIG_BLK_DEV_RAM_DAX

	gfp_flags |= __GFP_HIGHMEM;

#endif

	page = alloc_page(gfp_flags);

	page = alloc_page(gfp_flags);

	if (!page)

	if (!page)

		return NULL;

		return NULL;
@@ -334,43 +323,6 @@ static int brd_rw_page(struct block_device *bdev, sector_t sector, 
	return err;

	return err;

}

}





#ifdef CONFIG_BLK_DEV_RAM_DAX

static long __brd_direct_access(struct brd_device *brd, pgoff_t pgoff,

		long nr_pages, void **kaddr, pfn_t *pfn)

{

	struct page *page;



	if (!brd)

		return -ENODEV;

	page = brd_insert_page(brd, (sector_t)pgoff << PAGE_SECTORS_SHIFT);

	if (!page)

		return -ENOSPC;

	*kaddr = page_address(page);

	*pfn = page_to_pfn_t(page);



	return 1;

}



static long brd_dax_direct_access(struct dax_device *dax_dev,

		pgoff_t pgoff, long nr_pages, void **kaddr, pfn_t *pfn)

{

	struct brd_device *brd = dax_get_private(dax_dev);



	return __brd_direct_access(brd, pgoff, nr_pages, kaddr, pfn);

}



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

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

{

	return copy_from_iter(addr, bytes, i);

}



static const struct dax_operations brd_dax_ops = {

	.direct_access = brd_dax_direct_access,

	.copy_from_iter = brd_dax_copy_from_iter,

};

#endif



static const struct block_device_operations brd_fops = {

static const struct block_device_operations brd_fops = {

	.owner =		THIS_MODULE,

	.owner =		THIS_MODULE,

	.rw_page =		brd_rw_page,

	.rw_page =		brd_rw_page,
@@ -450,21 +402,8 @@ static struct brd_device *brd_alloc(int i) 
	sprintf(disk->disk_name, "ram%d", i);

	sprintf(disk->disk_name, "ram%d", i);

	set_capacity(disk, rd_size * 2);

	set_capacity(disk, rd_size * 2);





#ifdef CONFIG_BLK_DEV_RAM_DAX

	queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue);

	brd->dax_dev = alloc_dax(brd, disk->disk_name, &brd_dax_ops);

	if (!brd->dax_dev)

		goto out_free_inode;

#endif





	return brd;

	return brd;





#ifdef CONFIG_BLK_DEV_RAM_DAX

out_free_inode:

	kill_dax(brd->dax_dev);

	put_dax(brd->dax_dev);

#endif

out_free_queue:

out_free_queue:

	blk_cleanup_queue(brd->brd_queue);

	blk_cleanup_queue(brd->brd_queue);

out_free_dev:

out_free_dev:
@@ -504,10 +443,6 @@ static struct brd_device *brd_init_one(int i, bool *new) 
static void brd_del_one(struct brd_device *brd)

static void brd_del_one(struct brd_device *brd)

{

{

	list_del(&brd->brd_list);

	list_del(&brd->brd_list);

#ifdef CONFIG_BLK_DEV_RAM_DAX

	kill_dax(brd->dax_dev);

	put_dax(brd->dax_dev);

#endif

	del_gendisk(brd->brd_disk);

	del_gendisk(brd->brd_disk);

	brd_free(brd);

	brd_free(brd);

}

}