linux-ext4 - Re: [RFC PATCH] coredump: avoid ext4 auto_da

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Message-ID: <20160704151137.GE29557@thunk.org>
Date:	Mon, 4 Jul 2016 11:11:37 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Omar Sandoval <osandov@...ndov.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org, kernel-team@...com
Subject: Re: [RFC PATCH] coredump: avoid ext4 auto_da_alloc for core file

On Sun, Jul 03, 2016 at 10:24:55PM -0400, Theodore Ts'o wrote:
> From bf21c027d84ded545d2c08fa01fd184d29641458 Mon Sep 17 00:00:00 2001
> From: Theodore Ts'o <tytso@....edu>
> Date: Sun, 3 Jul 2016 22:20:49 -0400
> Subject: [PATCH] ext4: in ext4_setattr(), only call ext4_truncate() if there is no data to drop
> 
> If there are no blocks associated with the inode (and no inline data),
> there's no point calling ext4_truncate().  This avoids setting the
> replace-via-truncate hueristic if there is an attempt to truncate a
> file which is already zero-length --- which is something that happens
> in the core dumping code, in case there is an already existing core
> file.  In the comon case, there is not a previous core file, so by not
> enabling the replace-via-truncate hueristic, we can speed up core
> dumps.
> 
> Reported-by: Omar Sandoval <osandov@...com>
> Signed-off-by: Theodore Ts'o <tytso@....edu>

This patch is buggy; when I tried running regression tests, it failed
early.  So you probably want to skip this.

					- Ted
					
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