On 08/25/2011 06:35 PM, Dave Chinner wrote:
Agreed, that's the way I'd interpret it, too. So perhaps we need to ensure that this interpretation is actually tested by this test? How about some definitions to work by: Data: a range of the file that contains valid data, regardless of whether it exists in memory or on disk. The valid data can be preceeded and/or followed by an arbitrary number of zero bytes dependent on the underlying implementation of hole detection. Hole: a range of the file that contains no data or is made up entirely of NULL (zero) data. Holes include preallocated ranges of files that have not had actual data written to them. Does that make sense? It has sufficient flexibility in it for the existing generic "non-implementation", allows for filesystems to define their own hole detection boundaries (e.g. filesystem block size), and effectively defines how preallocated ranges from fallocate() should be treated (i.e. as holes). If we can agree on those definitions, I think that we should document them in both the kernel and the man page that defines SEEK_HOLE/SEEK_DATA so everyone is on the same page...
We should not tie in the definition to existing fs technologies. Instead we should let the fs weigh the cost of providing accurate information with the possible gain in performance. Data: A range in a file that could contain something other than nulls. If in doubt, it is data. Hole: A range in a file that only contains nulls. -- 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
