On Mon, Feb 11, 2019 at 10:43:06AM +0100, Carlos Maiolino wrote: > - The general idea, is to provide a way for FIEMAP ioctls to return the device > id where each extent is physically located. How does userspace get to use this information? If I call fiemap() and it tells me extent 1 is on device 0x12345678 and extent 2 is on device 0x34567812, what can I do with that information? Bear in mind that glibc uses a different dev_t from the kernel. > - This is particularly useful for those filesystems where the file extents are > located on a different block device other than that associated with the > superblock , for example, btrfs using multiple devices, and XFS when using a > real-time device. Darrick said it was useful for _inside_ the kernel. How is it useful for outside the kernel?
