> > > > In summary: > > > > - Applications must call statx to discover the current S_DAX state. > > Ok. > > > - There exists an advisory file inode flag FS_XFLAG_DAX that is set based on > > the parent directory FS_XFLAG_DAX inode flag. (There is no way to change > > this flag after file creation.) > > > > If FS_XFLAG_DAX is set and the fs is on pmem then it will enable S_DAX at > > inode load time; if FS_XFLAG_DAX is not set, it will not enable S_DAX. > > Unless overridden... > > Ok, fine with me. :) :-D > > > - There exists a dax= mount option. > > > > "-o dax=off" means "never set S_DAX, ignore FS_XFLAG_DAX" > > "-o nodax" means "dax=off" > > I surveyed the three fses that support dax and found that none of the > filesystems actually have a 'nodax' flag. Now would be the time not to > add such a thing, and make people specify dax=off instead. It would > be handy if we could have a single fsparam_enum for figuring out the dax > mount options. yes good point. I'm working on updating the documentation patch and I think this might also be better as: -o dax=never Which is the opposite of 'always'. > > > "-o dax=always" means "always set S_DAX (at least on pmem), ignore FS_XFLAG_DAX" > > "-o dax" by itself means "dax=always" > > "-o dax=iflag" means "follow FS_XFLAG_DAX" and is the default > > > > - There exists an advisory directory inode flag FS_XFLAG_DAX that can be > > changed at any time. The flag state is copied into any files or > > subdirectories when they are created within that directory. If programs > > require file access runs in S_DAX mode, they'll have to create those files > > "...they must create..." yes > > > inside a directory with FS_XFLAG_DAX set, or mount the fs with an > > appropriate dax mount option. > > Otherwise seems ok to me. Thanks! Ira
