From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Since this is relating to FS_XIP, not KERNEL_XIP, it should be called
DAX instead of XIP.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
---
drivers/block/Kconfig | 13 +++++++------
drivers/block/brd.c | 14 +++++++-------
fs/Kconfig | 4 ++--
3 files changed, 16 insertions(+), 15 deletions(-)
diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 014a1cf..1b8094d 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -393,14 +393,15 @@ config BLK_DEV_RAM_SIZE
The default value is 4096 kilobytes. Only change this if you know
what you are doing.
-config BLK_DEV_XIP
- bool "Support XIP filesystems on RAM block device"
- depends on BLK_DEV_RAM
+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 XIP filesystems (such as ext2 with XIP support on) on
- top of block ram device. This will slightly enlarge the kernel, and
- will prevent RAM block device backing store memory from being
+ 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
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 78fe510..97c55db 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -97,13 +97,13 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
* Must use NOIO because we don't want to recurse back into the
* block or filesystem layers from page reclaim.
*
- * Cannot support XIP and highmem, because our ->direct_access
- * routine for XIP must return memory that is always addressable.
- * If XIP was reworked to use pfns and kmap throughout, this
+ * Cannot support DAX and highmem, because our ->direct_access
+ * routine for DAX must return memory that is always addressable.
+ * If DAX was reworked to use pfns and kmap throughout, this
* restriction might be able to be lifted.
*/
gfp_flags = GFP_NOIO | __GFP_ZERO;
-#ifndef CONFIG_BLK_DEV_XIP
+#ifndef CONFIG_BLK_DEV_RAM_DAX
gfp_flags |= __GFP_HIGHMEM;
#endif
page = alloc_page(gfp_flags);
@@ -369,7 +369,7 @@ static int brd_rw_page(struct block_device *bdev, sector_t sector,
return err;
}
-#ifdef CONFIG_BLK_DEV_XIP
+#ifdef CONFIG_BLK_DEV_RAM_DAX
static long brd_direct_access(struct block_device *bdev, sector_t sector,
void **kaddr, unsigned long *pfn, long size)
{
@@ -388,6 +388,8 @@ static long brd_direct_access(struct block_device *bdev, sector_t sector,
* file happens to be mapped to the next page of physical RAM */
return PAGE_SIZE;
}
+#else
+#define brd_direct_access NULL
#endif
static int brd_ioctl(struct block_device *bdev, fmode_t mode,
@@ -428,9 +430,7 @@ static const struct block_device_operations brd_fops = {
.owner = THIS_MODULE,
.rw_page = brd_rw_page,
.ioctl = brd_ioctl,
-#ifdef CONFIG_BLK_DEV_XIP
.direct_access = brd_direct_access,
-#endif
};
/*
diff --git a/fs/Kconfig b/fs/Kconfig
index a9eb53d..117900f 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -34,7 +34,7 @@ source "fs/btrfs/Kconfig"
source "fs/nilfs2/Kconfig"
config FS_DAX
- bool "Direct Access support"
+ bool "Direct Access (DAX) support"
depends on MMU
help
Direct Access (DAX) can be used on memory-backed block devices.
@@ -45,7 +45,7 @@ config FS_DAX
If you do not have a block device that is capable of using this,
or if unsure, say N. Saying Y will increase the size of the kernel
- by about 2kB.
+ by about 5kB.
endif # BLOCK
--
2.1.0
--
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