On Sun, Jun 21, 2015 at 06:21:50AM -0700, Dan Williams wrote: > This question has come up before. Making btt an internal property of > a device makes some things cleaner and others more messy. We lose the > ability to place a btt instance on top of a partition, rather than a > whole disk. I thought the addition of nfit labels avoids the need for a partition table now? > If we ever need to access the raw device we no longer > have a direct block device to reference. Linux has been doing stacked > configurations to change the personality of block devices since > forever (md, dm, bcache...), why invent something new to handle the > btt-personality of ->rw_bytes() devices? Because the underlying abstraction really isn't a block device anymore, it's a byte addressable device. This is more similar to for example how the mtd subsystem is structured. > BTT precludes DAX, if you want both modes on one pmem disk placing BTT > on a partition of the disk for fs metadata and DAX-capable data on the > rest is our proposed solution. We chose this architecture after a > conversation with Dave Chinner about XFS's need to have atomic sector > guarantees for its metadata and wanting to simultaneously enable > XFS-DAX. I can't see why a v5 XFS filesystem with CRCs on all metadata would need sector atomic updates any more. But even in a case where it would it seem like whatever label you use for partioning should sit above the block layer. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
