Re: [PATCH] mkfs.xfs.8: clarify DAX-vs-reflink restrictions in the mkfs.xfs man page
From: "Darrick J. Wong" <djwong@kernel.org>
Date: 2021-08-27 15:49:08
On Fri, Aug 27, 2021 at 10:39:18AM -0500, Eric Sandeen wrote:
quoted hunk ↗ jump to hunk
Now that we have the tristate dax mount options, it is possible to enable DAX mode for non-reflinked files on a reflink-capable filesystem. Clarify this in the mkfs.xfs manpage. Reported-by: Bill O'Donnell <redacted> Signed-off-by: Eric Sandeen <redacted> ---diff --git a/man/man8/mkfs.xfs.8 b/man/man8/mkfs.xfs.8 index a7f70285..84ac50e8 100644 --- a/man/man8/mkfs.xfs.8 +++ b/man/man8/mkfs.xfs.8@@ -316,12 +316,20 @@ option set. When the option is used, the reference count btree feature is not supported and reflink is disabled. .IP -Note: the filesystem DAX mount option ( +Note: the filesystem-wide DAX mount options ( .B \-o dax -) is incompatible with -reflink-enabled XFS filesystems. To use filesystem DAX with XFS, specify the +and +.B \-o dax=always +) are incompatible with +reflink-enabled XFS filesystems. To use filesystem-wide DAX with XFS, specify the .B \-m reflink=0 option to mkfs.xfs to disable the reflink feature. +Alternatey, use the
"Alternately..."
+.B \-o dax=inode +mount option to selectively enable DAX mode on non-reflinked files.
/me wonders if this is dangerously close to wading into the muck that is "Use dax=inode or even no dax option at all, then make sure nobody shares your file's data blocks to set the DAX fsxattr flag on the file, and /then/ you can have DAX." <shrug> But the only blocker I can see is the misspelling above. --D
+See +.BR xfs (5) +for more information. .RE .PP .PD 0