On Sun, May 25, 2008 at 03:42:03PM -0400, Christoph Hellwig wrote: > > * FIEMAP_FLAG_LUN_ORDER > > If the file system stripes file data, this will return contiguous > > regions of physical allocation, sorted by LUN. Logical offsets may not > > make sense if this flag is passed. If the file system does not support > > multiple LUNs, this flag will be ignored. > > A LUN doesn't make any sense in filesystem context. That's a > scsi-centric acronym that doesn't even make sense in a scsi-centric > filesystem universe because a LUN can of course contain multiple > partitions. It's also extremly ill-defined when using volume managers. > > There's also no filesystems that actually support a single file on > multiple device in mainline, the only filesystem that supports multiple > data devices at all (XFS) requires each file to be on a single device. > > Once we have a filesystem with real multiple data device support like > btrfs or a future XFS version we can worry about this and defined > a different ioctl for it. > > > > > Each extent is described by a single fiemap_extent structure as > > returned in fm_extents. > > > > struct fiemap_extent { > > __u64 fe_logical;/* logical offset in bytes for the start of > > * the extent */ > > __u64 fe_physical; /* physical offset in bytes for the start > > * of the extent */ > > __u64 fe_length; /* length in bytes for the extent */ > > __u32 fe_flags; /* returned FIEMAP_EXTENT_* flags for the extent */ > > __u32 fe_lun; /* logical device number for extent (starting at 0)*/ > > Again this lun thing is horribly ill-defined. There is no such thing > as a logic device number in our filesystem terminology. The vxfs filesystem is capable of having each extent in a file on a different device. However, I don't think freevxfs supports that. I do agree that calling each one a "lun" is not really meaningful. Brad Boyer flar@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html