linux-kernel - Re: [PATCH 1/8] vfs: remove lock and unlock functions for super block

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Message-ID: <502CE700.3070709@panasas.com>
Date:	Thu, 16 Aug 2012 15:26:40 +0300
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	Marco Stornelli <marco.stornelli@...il.com>
CC:	<bhalevy@...ian.com>, <jack@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<adilger.kernel@...ger.ca>, <tytso@....edu>,
	<hirofumi@...l.parknet.co.jp>, <mikulas@...ax.karlin.mff.cuni.cz>,
	Al Viro <viro@...IV.linux.org.uk>, <hch@...radead.org>,
	<dushistov@...l.ru>, <osd-dev@...n-osd.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	<linux-ext4@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 1/8] vfs: remove lock and unlock functions for super block

On 08/16/2012 12:59 PM, Marco Stornelli wrote:

> From: Marco Stornelli <marco.stornelli@...il.com>
> 
> Remove lock_super and unlock_super from VFS.
> 
> Signed-off-by: Marco Stornelli <marco.stornelli@...il.com>


You can't remove the lock here. After this patch the tree will
not compile, and will not be bisectable. You must move this patch
to be last.

Each patch should leave the tree compileable and with out any
regressions.

Boaz

> ---
> 
> diff -Nurp linux-3.6-rc1-orig/fs/super.c linux-3.6-rc1/fs/super.c
> --- linux-3.6-rc1-orig/fs/super.c	2012-08-16 09:37:35.000000000 +0200
> +++ linux-3.6-rc1/fs/super.c	2012-08-16 09:43:46.000000000 +0200
> @@ -186,15 +186,8 @@ static struct super_block *alloc_super(s
>  		spin_lock_init(&s->s_inode_lru_lock);
>  		INIT_LIST_HEAD(&s->s_mounts);
>  		init_rwsem(&s->s_umount);
> -		mutex_init(&s->s_lock);
>  		lockdep_set_class(&s->s_umount, &type->s_umount_key);
>  		/*
> -		 * The locking rules for s_lock are up to the
> -		 * filesystem. For example ext3fs has different
> -		 * lock ordering than usbfs:
> -		 */
> -		lockdep_set_class(&s->s_lock, &type->s_lock_key);
> -		/*
>  		 * sget() can have s_umount recursion.
>  		 *
>  		 * When it cannot find a suitable sb, it allocates a new
> @@ -400,22 +393,6 @@ bool grab_super_passive(struct super_blo
>  	return false;
>  }
>  -/*
> - * Superblock locking.  We really ought to get rid of these two.
> - */
> -void lock_super(struct super_block * sb)
> -{
> -	mutex_lock(&sb->s_lock);
> -}
> -
> -void unlock_super(struct super_block * sb)
> -{
> -	mutex_unlock(&sb->s_lock);
> -}
> -
> -EXPORT_SYMBOL(lock_super);
> -EXPORT_SYMBOL(unlock_super);
> -
>  /**
>   *	generic_shutdown_super	-	common helper for ->kill_sb()
>   *	@sb: superblock to kill
> 
> diff -Nurp linux-3.6-rc1-orig/include/linux/fs.h linux-3.6-rc1/include/linux/fs.h
> --- linux-3.6-rc1-orig/include/linux/fs.h	2012-08-16 11:38:42.000000000 +0200
> +++ linux-3.6-rc1/include/linux/fs.h	2012-08-16 09:45:18.000000000 +0200
> @@ -1504,7 +1504,6 @@ struct super_block {
>  	unsigned long		s_magic;
>  	struct dentry		*s_root;
>  	struct rw_semaphore	s_umount;
> -	struct mutex		s_lock;
>  	int			s_count;
>  	atomic_t		s_active;
>  #ifdef CONFIG_SECURITY


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