linux-ext4 - Re: [PATCH, RFC] ext4: Automatically allocate delay allocated blocks on close

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Message-id: <20090224101344.GN3199@webber.adilger.int>
Date:	Tue, 24 Feb 2009 03:13:44 -0700
From:	Andreas Dilger <adilger@....com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, aneesh.kumar@...ux.vnet.ibm.com
Subject: Re: [PATCH, RFC] ext4: Automatically allocate delay allocated	blocks
 on close

On Feb 24, 2009  00:05 -0500, Theodore Ts'o wrote:
> When closing a file that had been previously truncated, force any
> delay allocated blocks that to be allocated so that if the filesystem
> is mounted with data=ordered, the data blocks will be pushed out to
> disk along with the journal commit.  Many application programs expect
> this, so we do this to avoid zero length files if the system crashes
> unexpectedly.

Should this only be done with "truncate-to-zero" operations, or any
truncate?  Some applications may do extending truncates in order to
trigger file preallocation ala Windows, and we don't necessarily want
to punish all of the IO for those files.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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