linux-ext4 - Re: [PATCH 2/5 v2] e2fsprogs: Use punch hole as "discard" on regular files

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Message-ID: <20110916035056.GT28181@thunk.org>
Date:	Thu, 15 Sep 2011 23:50:56 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-ext4@...r.kernel.org, adilger@...ger.ca
Subject: Re: [PATCH 2/5 v2] e2fsprogs: Use punch hole as "discard" on
 regular files

On Fri, Aug 12, 2011 at 06:42:57PM +0200, Lukas Czerner wrote:
> If e2fsprogs tools (mke2fs, e2fsck) is run on regular file instead of
> on block device, we can use punch hole instead of regular discard
> command which would not work on regular file anyway. This gives us
> several advantages. First of all when e2fsck is run with '-E discard'
> parameter it will punch out all ununsed space from the image, hence
> trimming down the file system image. And secondly, when creating an
> file system on regular file (with '-E discard' which is default), we
> can use punch hole to clear the file content, hence we can skip inode
> table initialization, because reads from sparse area returns zeros. This
> will result in faster file system creation (without the need to specify
> lazy_itable_init) and smaller images.
> 
> This commit also fixes some tests that would fail due to mke2fs showing
> discard progress, hence the output would differ.
> 
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>

Applied to the next branch, thanks.  (I combined the following patch
which added the configure.in test for linux/falloc.h, since it's
needed by this patch.)

					- Ted
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