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@xxxxxxxxx>
Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/block/Kconfig | 12 ---------
drivers/block/brd.c | 65 -------------------------------------------------
2 files changed, 77 deletions(-)
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 2dfe99b328f8..da8bf0268ade 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -297,7 +297,6 @@ config BLK_DEV_SX8
config BLK_DEV_RAM
tristate "RAM block device support"
- select DAX if BLK_DEV_RAM_DAX
---help---
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
@@ -333,17 +332,6 @@ config BLK_DEV_RAM_SIZE
The default value is 4096 kilobytes. Only change this if you know
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
tristate "Packet writing on CD/DVD media (DEPRECATED)"
depends on !UML
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 2d7178f7754e..b2391bbd7e5a 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -20,11 +20,6 @@
#include <linux/radix-tree.h>
#include <linux/fs.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>
@@ -44,9 +39,6 @@ struct brd_device {
struct request_queue *brd_queue;
struct gendisk *brd_disk;
-#ifdef CONFIG_BLK_DEV_RAM_DAX
- struct dax_device *dax_dev;
-#endif
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.
*/
gfp_flags = GFP_NOIO | __GFP_ZERO;
-#ifndef CONFIG_BLK_DEV_RAM_DAX
- gfp_flags |= __GFP_HIGHMEM;
-#endif
page = alloc_page(gfp_flags);
if (!page)
return NULL;
@@ -334,43 +323,6 @@ static int brd_rw_page(struct block_device *bdev, sector_t sector,
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 = {
.owner = THIS_MODULE,
.rw_page = brd_rw_page,
@@ -450,21 +402,8 @@ static struct brd_device *brd_alloc(int i)
sprintf(disk->disk_name, "ram%d", i);
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;
-#ifdef CONFIG_BLK_DEV_RAM_DAX
-out_free_inode:
- kill_dax(brd->dax_dev);
- put_dax(brd->dax_dev);
-#endif
out_free_queue:
blk_cleanup_queue(brd->brd_queue);
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)
{
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);
brd_free(brd);
}
--
To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
