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From: Borsenkow Andrej <Andrej.Borsenkow@mow.siemens.ru>
To: "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>
Subject: How safe is to add a member to struct super_block?
Date: Wed, 5 Jun 2002 10:24:58 +0400 
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There is a problem in media revalidation in current supermount - if
something tries to access device after media change before supermount (a
reported case was - close tray manually and do eject -t) a "media change"
flag is lost so supermount never remounts underlying fs.

The simplest way to fix it is to unmount filesystem in check_media_change
(actually in destroy_device where we get superblock). But this needs both a
"this fs is supermounted" flag and pointer to top-level fs so supermount can
properly clean up. So I intend to add a member to struct super_block that
points to super block of top-level (supermount) fs.

Are there any alignment/size constraints on struct super_block to be aware
of?

TIA

-andrej
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