fuse: add extent map data structure

Add support for creating and managing extent maps that map file regions to
dax device regions.

Introduce FUSE_NOTIFY_BACKING_MAP for populating extent maps from
userspace.

Extent maps are handled as a new type of backing and are assigned a 64 bit
backing ID by the server.

One extent consists of

 - offset within the containing backing
 - length of extent
 - target backing ID
 - offset into target backing

Extents must be non-overlapping, and can only refer to dax device backings
for now.

At this point only support creating and populating the extent map in one
operation, though the interface is not limited by this and later may be
changed, so that partial population of an extent map would be possible.

Originally-by: John Groves <john@groves.net>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

0 files changed, 0 insertions, 0 deletions