Re: [CFT][PATCH] loopback fixes for 2.3

From: Andi Kleen (ak@muc.de)
Date: Sat Feb 12 2000 - 09:45:19 EST


On Sat, Feb 12, 2000 at 12:00:08PM +0100, Alexander Viro wrote:
> --- linux-2.3.44-pre8/drivers/block/loop.c Thu Feb 10 16:42:11 2000
> +++ linux-bird.vm/drivers/block/loop.c Sat Feb 12 03:41:27 2000
> @@ -40,6 +40,10 @@
> * it passes the underlying device's block number instead of the
> * offset. This makes it change for a given block when the file is
> * moved/restored/copied and also doesn't work over NFS.
> + * AV, Feb 11, 2000: for files we pass the page index now. It should fix the
> + * problem above. Since the granularity is PAGE_CACHE_SIZE now it seems to
> + * be correct way. OTOH, taking the thing from x86 to Alpha may become
> + * interesting, so we might want to rethink it.

You cannot do that. That will break all encrypted files that use the
passed index as IV. It is already part of the disk format. The only
way to change it is to add new vectors to loop_func_table and keep
the absolute offset for the old files. Then new encryption modules
could use the changed format, but old ones would still work with the
known limitations.

-Andi

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