Documentation/filesystems/dax.txt

31 When mounting the filesystem, use the "-o dax" option on the command line or
32 add 'dax' to the options in /etc/fstab.  This works to enable DAX on all files
33 within the filesystem.  It is equivalent to the '-o dax=always' behavior below.
56  4. There exist dax mount options which can override FS_XFLAG_DAX in the
60     "-o dax=inode"  means "follow FS_XFLAG_DAX" and is the default.
62     "-o dax=never"  means "never set S_DAX, ignore FS_XFLAG_DAX."
64     "-o dax=always" means "always set S_DAX ignore FS_XFLAG_DAX."
66     "-o dax"        is a legacy option which is an alias for "dax=always".
67 		    This may be removed in the future so "-o dax=always" is
71     the same even when the filesystem is mounted with a dax option.  However,
73     remounted with dax=inode and the inode is evicted from kernel memory.
80     b) Setting the appropriate dax="foo" mount option
105 There are 2 per-file dax flags.  One is a persistent inode setting (FS_XFLAG_DAX)
127 	dax: a,e
128 	no dax: b,c,d
136 	dax: a,b,c,d
137 	no dax:
145 	dax: c,d
146 	no dax: a,b
151 value of FS_XFLAG_DAX and the filesystem's dax mount option.
158 if the underlying media does not support dax and/or the filesystem is