linux-kernel - Re: [RFC][PATCH 4/5] must hold lock_super() to set initial mount writer

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Message-Id: <E1Jr8ZK-0001uW-4s@pomaz-ex.szeredi.hu>
Date:	Wed, 30 Apr 2008 11:25:42 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	dave@...ux.vnet.ibm.com
CC:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	viro@...iv.linux.org.uk, hch@...radead.org,
	trond.myklebust@....uio.no, dave@...ux.vnet.ibm.com
Subject: Re: [RFC][PATCH 4/5] must hold lock_super() to set initial mount writer

> We need lock_mnt_writers() during a remount in order
> to keep mnt->__mnt_writers from changing so that we
> get a consistent look at if a sb currently has anyone
> writing to it.
> 
> But, we need to lock writers out for an extended
> period, even during the ->remount_fs() operation.
> That's because we do conclusively make the fs
> r/o until *after* the ->remount_fs().

So?  Why don't we mark the fs r/o _before_ calling ->remount_fs() and
if that fails, just mark it r/w again.

OK, we'll deny writes in that interval, but I don't see that as a big
problem.  And it would simplify the implementation considerably.

Miklos
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