Re: Bug in 2.1 loop block dev?
Matthew Wilcox (willy@odie.barnet.ac.uk)
Sat, 8 Aug 1998 00:28:50 +0100 (BST)
From: Andrew McNamara <andrewm@connect.com.au>
> I suspect there is a bug in the loopback blockdev - when a file is
> released as a loop blockdev, the cached pages aren't invalidated.
>
> This manifested itself when I was working on a filesystem module - I
> was using the loopback dev to map an file containing an existing fs - I
> switched between mounting an 800K floppy image to a 32M hard disk
> image, but the superblock was still claiming to be only 800k.
>
> This turned out to be duplicatable - any blocks read and still in the
> cache would remain after the loop device was released then reconnected
> to another file.
>
> This was about 2.1.80 - I've been meaning to look further into the
> problem since then, and hopefully post a fix, but I haven't had time.
> With the approch of 2.2, I hope someone can take a quick look at this
> and see if they also can duplicate it - there doesn't appear to be
> a current maintainer.
I think this may be related to the situation I discovered where I was
able to unmount a filesystem which still had an active loopback mount
on it. I fixed the cause of this and it may have fixed your bug too.
Please try a kernel later than 2.1.107 to find out.
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