Re: [PATCH 1/4] vfs: vfs-level fiemap interface

[Christoph Hellwig <hch@infradead.org>]

On Mon, Oct 06, 2008 at 05:07:06PM -0400, Theodore Tso wrote:
> +* FIEMAP_EXTENT_NO_UNMOUNTED_IO
> +Accessing the data in this extent via I/O to the block device while the
> +filesystem is unmounted is illegal or will have undefined results.  This
> +may be because the data is somehow encrypted or compressed by the filesystem.
> +Note that accessing the data using the information returned by the
> +FIEMAP interface while the filesystem is mounted is *always* undefined
> +should not be attempted by user applications. 

I think the point we're trying to get down to is that this is not just a
normal block that you can access using a block number but some
complicated encoding scheme.  Maybe

* FIEMAP_EXTENT_ENCODED

This extent does not consistant of plain filesystem blocks but is
encoded (e.g. encrypted or compressed) or shared with other data by the
filesystem.  Accessing the data in this extent via I/O to the block
device will have undefined resuts. Note that accessing the data using
the information returned by the FIEMAP interface while the filesystem is
mounted is *always* undefined should not be attempted by user applications.


Except for continuous nitpicking about this flag which could be
continued in mainline before a release this patch looks good to me.