Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO_RANGE flag for fallocate

Christoph Hellwig
2014-04-16T06:36:30Z

On Mon, Feb 17, 2014 at 04:08:17PM +0100, Lukas Czerner wrote:
> Introduce new FALLOC_FL_ZERO_RANGE flag for fallocate. This has the same
> functionality as xfs ioctl XFS_IOC_ZERO_RANGE.

Lukas, can you please also send a man page update for
FALLOC_FL_ZERO_RANGE now that is has been merged?

>
> It can be used to convert a range of file to zeros preferably without
> issuing data IO. Blocks should be preallocated for the regions that span
> holes in the file, and the entire range is preferable converted to
> unwritten extents - even though file system may choose to zero out the
> extent or do whatever which will result in reading zeros from the range
> while the range remains allocated for the file.
>
> This can be also used to preallocate blocks past EOF in the same way as
> with fallocate. Flag FALLOC_FL_KEEP_SIZE which should cause the inode
> size to remain the same.
>
> You can test this feature yourself using xfstests, of fallocate(1) however
> you'll need patches for util_linux, xfsprogs and xfstests which you
> can find here:
>
> http://people.redhat.com/lczerner/zero_range/