linux-ext4 - Re: [PATCH 04/27] ext2: Add ext2_sb

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Date:	Mon, 2 Nov 2009 17:57:52 +0100
From:	Jan Blunck <jblunck@...e.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-fsdevel@...r.kernel.org, Matthew Wilcox <matthew@....cx>,
	linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Christoph Hellwig <hch@....de>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andreas Dilger <adilger@....com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 04/27] ext2: Add ext2_sb_info mutex

On Mon, Nov 02, Andi Kleen wrote:

> > @@ -762,6 +767,12 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
> >  	sbi->s_sb_block = sb_block;
> >  
> >  	/*
> > +	 * mutex for protection of modifications of the superblock while being
> > +	 * write out by ext2_write_super() or ext2_sync_fs().
> > +	 */
> > +	mutex_init(&sbi->s_mutex);
> 
> I didn't go over all the code paths in detail, but if you replace
> the BKL with a mutex that is hold over a longer write-out sleep
> period you potentially limit IO parallelism a lot.

Right. I converted it to be a spinlock and unlock before calling
ext2_sync_super().

What do you think?

Thanks,
Jan

View attachment "0005-ext2-Add-ext2_sb_info-spinlock.patch" of type "text/x-patch" (7271 bytes)