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| author | Christoph Hellwig <hch@lst.de> | 2021-08-26 15:55:02 +0200 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2021-08-26 16:52:02 -0700 |
| commit | 6c97ec172a1c058a66e7c79308a0d7f11753865d (patch) | |
| tree | f50db1aea60a5068ca8e1c896018a87fc75be0cc /fs/Kconfig | |
| parent | 7c60610d476766e128cc4284bb6349732cbd6606 (diff) | |
| download | lwn-6c97ec172a1c058a66e7c79308a0d7f11753865d.tar.gz lwn-6c97ec172a1c058a66e7c79308a0d7f11753865d.zip | |
fsdax: improve the FS_DAX Kconfig description and help text
Rename the main option text to clarify it is for file system access,
and add a bit of text that explains how to actually switch a nvdimm
to a fsdax capable state.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210826135510.6293-2-hch@lst.de
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'fs/Kconfig')
| -rw-r--r-- | fs/Kconfig | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/fs/Kconfig b/fs/Kconfig index a7749c126b8e..bd21535a7620 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 |