From: Dan Williams <dan.j.williams@intel.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Mike Snitzer <snitzer@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
linux-xfs <linux-xfs@vger.kernel.org>,
Linux NVDIMM <nvdimm@lists.linux.dev>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-ext4 <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH 1/9] fsdax: improve the FS_DAX Kconfig description and help text
Date: Mon, 23 Aug 2021 11:45:52 -0700 [thread overview]
Message-ID: <CAPcyv4h0QdHi10ngaXtuisxeZ+66wd-oy0F7r9C0FjJmyXBOFg@mail.gmail.com> (raw)
In-Reply-To: <20210823123516.969486-2-hch@lst.de>
On Mon, Aug 23, 2021 at 5:37 AM Christoph Hellwig <hch@lst.de> wrote:
>
> 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.
>
Looks good, nice improvement. A couple suggestions below.
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/Kconfig | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index a7749c126b8e..37e4441119cf 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 +53,19 @@ 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
There's still the concern that on systems with small amount of DRAM
relative to large amounts of PMEM that --map=mem might consume all
available memory for 'struct page'. Perhaps just add:
"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 enable
> + globally or per-inode using a mount option as well. See the
> + file system documentation for details.
How about include the link?
"See the file system documentation for details:
https://www.kernel.org/doc/html/latest/filesystems/dax.html"
next prev parent reply other threads:[~2021-08-23 18:46 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-23 12:35 dax_supported() related cleanups Christoph Hellwig
2021-08-23 12:35 ` [PATCH 1/9] fsdax: improve the FS_DAX Kconfig description and help text Christoph Hellwig
2021-08-23 18:45 ` Dan Williams [this message]
2021-08-24 6:55 ` Christoph Hellwig
2021-08-23 12:35 ` [PATCH 2/9] dax: stop using bdevname Christoph Hellwig
2021-08-23 18:47 ` Dan Williams
2021-08-23 12:35 ` [PATCH 3/9] dm: use fs_dax_get_by_bdev instead of dax_get_by_host Christoph Hellwig
2021-08-23 19:02 ` Dan Williams
2021-08-23 12:35 ` [PATCH 4/9] dax: mark dax_get_by_host static Christoph Hellwig
2021-08-23 20:56 ` Dan Williams
2021-08-23 12:35 ` [PATCH 5/9] dax: move the dax_read_lock() locking into dax_supported Christoph Hellwig
2021-08-23 20:57 ` Dan Williams
2021-08-23 12:35 ` [PATCH 6/9] dax: remove __generic_fsdax_supported Christoph Hellwig
2021-08-23 21:10 ` Dan Williams
2021-08-23 12:35 ` [PATCH 7/9] dax: stub out dax_supported for !CONFIG_FS_DAX Christoph Hellwig
2021-08-23 21:15 ` Dan Williams
2021-08-24 5:44 ` Christoph Hellwig
2021-08-23 12:35 ` [PATCH 8/9] xfs: factor out a xfs_buftarg_is_dax helper Christoph Hellwig
2021-08-23 21:20 ` Dan Williams
2021-08-23 12:35 ` [PATCH 9/9] dax: remove bdev_dax_supported Christoph Hellwig
2021-08-23 21:22 ` Dan Williams
2021-08-26 13:55 dax_supported() related cleanups v2 Christoph Hellwig
2021-08-26 13:55 ` [PATCH 1/9] fsdax: improve the FS_DAX Kconfig description and help text Christoph Hellwig
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