linux-ext4 - Re: e4defrag and immutable files

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Date:	Tue, 01 Jun 2010 14:12:28 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	linux-ext4@...r.kernel.org
Subject: Re: e4defrag and immutable files

H. Peter Anvin wrote:
> Hi all,
> 
> I have looked a bit at e4defrag, and it does not appear to prevent the
> relocation of files marked immutable.  This is a problem for boot
> loaders, which may need to have a block pointer to a specific file in
> order to bootstrap themselves.
> 
> Would it be possible to either:
> 
> a) prevent e4defrag and/or EXT4_IOC_MOVE_EXT from relocating an
> immutable file, or
> b) add a new attribute with the above property (in case there is
> legitimate need to move around immutable files)?

seems like the immutable flag isn't necessarily the right thing to
key on; at least it's an addition to what the manpage says immutable
means...

>        A file with the ‘i’ attribute cannot be modified: it cannot
>        be  deleted or renamed, no link can be created to this file
>        and no data can be written to the file.  Only the superuser
>        or  a process possessing the CAP_LINUX_IMMUTABLE capability
>        can set or clear this attribute.

Changing the physical mapping doesn't do any of those things.

I think a new flag, no-move or something, may be better, if it's
needed.  But how many files would ever get this; maybe defragging
boot files falls into the category of "don't do that?" :)

-Eric

> 	-hpa

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