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

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Date:	Tue, 18 Feb 2014 20:41:42 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Lukáš 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 Tue, Feb 18, 2014 at 10:09:48AM +0100, Lukáš Czerner wrote:
> On Tue, 18 Feb 2014, Dave Chinner wrote:
> 
> > Date: Tue, 18 Feb 2014 19:33:24 +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 Tue, Feb 18, 2014 at 12:01:38PM +1100, Dave Chinner wrote:
> > > 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.
> 
> That was the plan originally, however it uses xfs bmap which is not
> supported for other file systems. But I can take a better look and
> possibly port it to generic as well.

Simply pass fiemap rather than "bmap -v" like all the other falloc
tests do. The output of the xfs_io fiemap and bmap commands is
pretty much identical so this shouldn't be an issue.

> > > > ./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;
> > 
> > FWIW. if that's a group of tests you consider good for testing
> > extent tree modifications, then can you create a test group for
> > these by adding "extent" to each of the tests in the group file?
> 
> I've made patches adding support for FALLOC_FL_ZERO_RANGE into fsx
> and fsstress so those tests are mostly tests which are using fsx and
> fsstress.

Ok, so it's a "fallocate" test group, then?

Cheers,

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