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authorLinus Torvalds <torvalds@linux-foundation.org>2021-09-09 21:39:57 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-09 21:39:57 +0300
commit2e5fd489a4e5fcc97b035c03ace724c1d481a4c1 (patch)
treede1705048e3d2c71c74b7547e149b2973ebb29e1 /fs/Kconfig
parent4b105f4a256ae629522a7ed1611aba28fd282bd5 (diff)
parent3fc3725357414636d91be1558ce8b14f228b4bda (diff)
downloadlinux-2e5fd489a4e5fcc97b035c03ace724c1d481a4c1.tar.xz
Merge tag 'libnvdimm-for-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm
Pull libnvdimm updates from Dan Williams: - Fix a race condition in the teardown path of raw mode pmem namespaces. - Cleanup the code that filesystems use to detect filesystem-dax capabilities of their underlying block device. * tag 'libnvdimm-for-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: dax: remove bdev_dax_supported xfs: factor out a xfs_buftarg_is_dax helper dax: stub out dax_supported for !CONFIG_FS_DAX dax: remove __generic_fsdax_supported dax: move the dax_read_lock() locking into dax_supported dax: mark dax_get_by_host static dm: use fs_dax_get_by_bdev instead of dax_get_by_host dax: stop using bdevname fsdax: improve the FS_DAX Kconfig description and help text libnvdimm/pmem: Fix crash triggered when I/O in-flight during unbind
Diffstat (limited to 'fs/Kconfig')
-rw-r--r--fs/Kconfig21
1 files changed, 18 insertions, 3 deletions
diff --git a/fs/Kconfig b/fs/Kconfig
index d8207a1b8c44..c854725db417 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -43,7 +43,7 @@ source "fs/f2fs/Kconfig"
source "fs/zonefs/Kconfig"
config FS_DAX
- bool "Direct Access (DAX) support"
+ bool "File system based Direct Access (DAX) support"
depends on MMU
depends on !(ARM || MIPS || SPARC)
select DEV_PAGEMAP_OPS if (ZONE_DEVICE && !FS_DAX_LIMITED)
@@ -53,8 +53,23 @@ config FS_DAX
Direct Access (DAX) can be used on memory-backed block devices.
If the block device supports DAX and the filesystem supports DAX,
then you can avoid using the pagecache to buffer I/Os. Turning
- on this option will compile in support for DAX; you will need to
- mount the filesystem using the -o dax option.
+ on this option will compile in support for DAX.
+
+ For a DAX device to support file system access it needs to have
+ struct pages. For the nfit based NVDIMMs this can be enabled
+ using the ndctl utility:
+
+ # ndctl create-namespace --force --reconfig=namespace0.0 \
+ --mode=fsdax --map=mem
+
+ See the 'create-namespace' man page for details on the overhead of
+ --map=mem:
+ https://docs.pmem.io/ndctl-user-guide/ndctl-man-pages/ndctl-create-namespace
+
+ For ndctl to work CONFIG_DEV_DAX needs to be enabled as well. For most
+ file systems DAX support needs to be manually enabled globally or
+ per-inode using a mount option as well. See the file documentation in
+ Documentation/filesystems/dax.rst for details.
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