linux-ext4 - Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO

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Date:	Tue, 18 Feb 2014 12:01:38 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-ext4@...r.kernel.org, tytso@....edu,
	linux-fsdevel@...r.kernel.org, xfs@....sgi.com
Subject: Re: [PATCH 0/6][RFC] Introduce FALLOC_FL_ZERO_RANGE flag for
 fallocate

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.
> 
> 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/
> 
> I'll post the patches after we agree and merge the kernel functionality.
> 
> I tested this mostly with a subset of xfstests using fsx and fsstress and
> even with new generic/290 which is just a copy of xfs/290 usinz fzero
> command for xfs_io instead of zero (which uses ioctl). I was testing on
> x86_64 and ppc64 with block sizes of 1024, 2048 and 4096.

You also want to convert xfs/242 to be a generic test - it uses the
_generic_test_punch helper to test all the corner cases across
different extent type transitions.

> ./check generic/076 generic/232 generic/013 generic/070 generic/269 generic/083 generic/117 generic/068 generic/231 generic/127 generic/091 generic/075 generic/112 generic/263 generic/091 generic/075 generic/256 generic/255 generic/316 generic/300 generic/290;
> 
> Note that there is a work in progress on FALLOC_FL_COLLAPSE_RANGE which
> touches the same area as this pach set does, so we should figure out
> which one should go first and modify the other on top of it.

I was going to push the FALLOC_FL_COLLAPSE_RANGE stuff through
the XFS tree once it was done - perhaps you and Namjae can get
together and work out which order the patch series should go.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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