Re: [PATCH 2/2] ->write_super lock_super pushdown

[Boaz Harrosh <bharrosh@panasas.com>]

On 05/12/2009 12:35 AM, Christoph Hellwig wrote:
> Push down lock_super into ->write_super instances and remove it from the
> caller.
> 
> Following filesystem don't need ->s_lock in ->write_super and are skipped:
> 
>  * bfs, nilfs2 - no other uses of s_lock and have internal locks in
> 	->write_super
>  * ext2 - uses BKL in ext2_write_super and has internal calls without s_lock
>  * reiserfs - no other uses of s_lock as has reiserfs_write_lock (BKL) in
>  	->write_super
>  * xfs - no other uses of s_lock and uses internal lock (buffer lock on
> 	superblock buffer) to serialize ->write_super.  Also xfs_fs_write_super 
> 	is superflous and will go away in the next merge window
> 
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> 

Ack-by Boaz Harrosh <bharrosh@panasas.com>

<snip>
> ===================================================================
> --- vfs-2.6.orig/fs/exofs/super.c	2009-05-11 23:26:24.971786995 +0200
> +++ vfs-2.6/fs/exofs/super.c	2009-05-11 23:28:12.929808342 +0200
> @@ -214,6 +214,7 @@ static void exofs_write_super(struct sup
>  		return;
>  	}
>  
> +	lock_super(sb);
>  	lock_kernel();
>  	sbi = sb->s_fs_info;
>  	fscb->s_nextid = cpu_to_le64(sbi->s_nextid);
> @@ -246,6 +247,7 @@ out:
>  	if (or)
>  		osd_end_request(or);
>  	unlock_kernel();
> +	unlock_super(sb);
>  	kfree(fscb);
>  }
>  

Please I have a question about this?

lock_super():
  I do not see any other lock_super() in exofs, so all this might "lock" is
  race against itself, right? Should I make sure that concurrent
  exofs_write_super are protected some other way and remove this?

lock_kernel();
  What is that used for? What should I check so this can be removed?

Sorry for the novice-ness ;-)

Thanks
Boaz