linux-kernel - Re: Access Control Lists for tmpfs

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Message-Id: <20060901145203.d3880d1d.akpm@osdl.org>
Date:	Fri, 1 Sep 2006 14:52:03 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Andreas Gruenbacher <agruen@...e.de>
Cc:	linux-kernel@...r.kernel.org, James Morris <jmorris@...ei.org>,
	Kay Sievers <kay.sievers@...y.org>
Subject: Re: Access Control Lists for tmpfs

On Sat, 02 Sep 2006 00:14:23 +0200
Andreas Gruenbacher <agruen@...e.de> wrote:

> +static void
> +shmem_set_acl(struct inode *inode, int type, struct posix_acl *acl)
> +{
> +	spin_lock(&inode->i_lock);
> +	switch(type) {
> +		case ACL_TYPE_ACCESS:
> +			if (SHMEM_I(inode)->i_acl)
> +				posix_acl_release(SHMEM_I(inode)->i_acl);
> +			SHMEM_I(inode)->i_acl = posix_acl_dup(acl);
> +			break;

i_lock is "general-purpose, innermost per-inode lock".  Calling kfree()
under it makes it no longer "innermost".  But kfree() is surely atomic wrt
everything which filesystems and the VFS will want to do, so that's OK.

However it does point at an inefficiency.  There's no need at all to be
holding onto that lock while running kfree().


-- 
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