From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [patch 2/4] fs: fsync inode dirty race fix
Date: Mon, 22 Nov 2010 08:23:18 -0500
Message-ID: <20101122132318.GB25321@infradead.org>
References: <20101122130507.GC12716@amd>
 <20101122130637.GD12716@amd>
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Cc: linux-fsdevel@vger.kernel.org
To: Nick Piggin <npiggin@kernel.dk>
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>  	ret = sync_mapping_buffers(inode->i_mapping);
> -	if (!(inode->i_state & I_DIRTY))
> -		return ret;
> -	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
> -		return ret;
> -
>
>  	err = sync_inode_metadata(inode, 1);

This makes fdatasync equivalent to fsync, which means a huge drop
in performance for database an virtualization performance.

I think the right aproach is to extend the sync_inode_metadata to
writeback_single_inode chain with a datasync parameter so that we
can do the correct decision there.

Note that there are a lot more fsync implementations than just
generic_file_fsync and exofs_fsync that have the same issue.