linux-ext4 - Re: [PATCH] ext4: Fix fallocate to update the file size in each transaction.

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Date:	Thu, 13 Mar 2008 09:04:19 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Andreas Dilger <adilger@....com>
CC:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	cmm@...ibm.com, tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: Fix fallocate to update the file size in each	transaction.

Andreas Dilger wrote:
> On Mar 11, 2008  11:25 +0530, Aneesh Kumar K.V wrote:
>> +	-x: run test after preallocating the area (1|2) 2 to not update size.\n\
> 
> The issue with preallocating just a single area in fsx is that this isn't
> much different than starting the test with a single large write or truncate.

except that the filesystem does still have to manage the unwritten
extent splits properly... but I agree that ongoing extending and
non-extending fallocates of various sizes would be very interesting.

-Eric

> What would be a lot more useful is to have fsx continually do fallocate
> requests of variable sizes during the test.  This would be quite similar
> to a "write" operation, except that it wouldn't change any existing data
> and holes would still read back as zero.  The only difference is in the
> "do not update size" test any fallocate at the end of the file would not
> increase the file size.
> 
> This would exercise the fallocate code a LOT because it would put unwritten
> extents in the middle of the file, map a single fallocate to multiple
> discontiguous holes of the file (not overwriting existing allocated data
> in the middle of the file), verify fallocate of an overlapping unwritten
> extent works, etc.
> 
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