From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>,
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: Tue, 24 Aug 2021 08:55:46 +0200 [thread overview]
Message-ID: <20210824065546.GA24465@lst.de> (raw)
In-Reply-To: <CAPcyv4h0QdHi10ngaXtuisxeZ+66wd-oy0F7r9C0FjJmyXBOFg@mail.gmail.com>
On Mon, Aug 23, 2021 at 11:45:52AM -0700, Dan Williams wrote:
> 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.
Does this looks ok?
---
From c69617137a1e6b67122c871c946e7aa00b03978b Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Mon, 23 Aug 2021 10:57:37 +0200
Subject: 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>
---
fs/Kconfig | 21 ++++++++++++++++++---
1 file 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
--
2.30.2
next prev parent reply other threads:[~2021-08-24 6:55 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
2021-08-24 6:55 ` Christoph Hellwig [this message]
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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