On Wed, Mar 10, 2021 at 6:27 AM Matthew Wilcox <willy(a)infradead.org> wrote:
On Wed, Mar 10, 2021 at 08:21:59AM -0600, Goldwyn Rodrigues wrote:
> On 13:02 10/03, Matthew Wilcox wrote:
> > On Wed, Mar 10, 2021 at 07:30:41AM -0500, Neal Gompa wrote:
> > > Forgive my ignorance, but is there a reason why this isn't wired up
> > > Btrfs at the same time? It seems weird to me that adding a feature
> > btrfs doesn't support DAX. only ext2, ext4, XFS and FUSE have DAX
> > If you think about it, btrfs and DAX are diametrically opposite things.
> > DAX is about giving raw access to the hardware. btrfs is about offering
> > extra value (RAID, checksums, ...), none of which can be done if the
> > filesystem isn't in the read/write path.
> > That's why there's no DAX support in btrfs. If you want DAX, you have
> > to give up all the features you like in btrfs. So you may as well use
> > a different filesystem.
> DAX on btrfs has been attempted. Of course, we could not
But why? A completeness fetish? I don't understand why you decided
to do this work.
Isn't DAX useful for pagecache minimization on read even if it is
awkward for a copy-on-write fs?
Seems it would be a useful case to have COW'd VM images on BTRFS that
don't need superfluous page cache allocations.