linux-kernel - Re: [PATCH] Support for secure erase functionality

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Message-ID: <20170914081757.c64qa6pp2zi5hmda@linux-x5ow.site>
Date:   Thu, 14 Sep 2017 10:17:57 +0200
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     Philipp Guendisch <philipp.guendisch@....de>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-block@...r.kernel.org, damien.lemoal@....com,
        axboe@...nel.dk, viro@...iv.linux.org.uk,
        bart.vanassche@...disk.com, martin.petersen@...cle.com,
        hare@...e.de, osandov@...com, dan.j.williams@...el.com,
        ming.lei@...hat.com, linux-kernel@...cs.fau.de,
        Mate Horvath <horvatmate@...il.com>
Subject: Re: [PATCH] Support for secure erase functionality

On Wed, Sep 13, 2017 at 05:37:53PM +0200, Philipp Guendisch wrote:
> This patch adds a software based secure erase option to improve data
> confidentiality. The CONFIG_BLK_DEV_SECURE_ERASE option enables a mount
> flag called 'sw_secure_erase'. When you mount a volume with this flag,
> every discard call is prepended by an explicit write command to overwrite
> the data before it is discarded. A volume without a discard compatibility
> can be used as well but the discard calls will be enabled for this device
> and suppressed after the write call is made.

How can this work with CoW filesystems?

> 
> Built against torvalds/linux

This should go below the '---' so git am doesn't write it into the changelog.


[...]

> +	if (strcmp(fs_type->name, "ext4") != 0 &&
> +	    strcmp(fs_type->name, "btrfs") != 0 &&
> +	    strcmp(fs_type->name, "gfs2") != 0 &&
> +	    strcmp(fs_type->name, "gfs2meta") != 0 &&
> +	    strcmp(fs_type->name, "xfs") != 0 &&
> +	    strcmp(fs_type->name, "jfs") != 0) {
> +		pr_warn("fs: The mounted %s filesystem on drive %s does not generate discards, secure erase won't work",
> +				fs_type->name, dev_name);
> +	}
> +skip:
> +#endif

Which filesystems commonly used in production are left afterwards?

I'm sorry, but while I get that this sounds like a nice feature for a paper or
reasearch project, I don't see why it should be used on production systems at
all.

Byte,
	Johannes
-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
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