DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:sender:in-reply-to:references:date
         :x-google-sender-auth:message-id:subject:from:to:cc:content-type
         :content-transfer-encoding;
        b=MkZWHUkIMcyoNGz4x3Z9t7qn8lyf9dPuzX0vXicadetCpUqzTmYHOrQBYpMGh3NPmf
         b0ZcwI1cA/aXHiXeoHkyDVI+B4QFY9mQJx+N/227gFlES9tAoUVkLNaEmjcIYx7cG8K3
         RVkPI8nMiUzTZzWfQ3AxZjzb7d4TVnS8Ey+54=
MIME-Version: 1.0
In-Reply-To: <20101116142029.528762151@kernel.dk>
References: <20101116140900.039761100@kernel.dk>
	<20101116142029.528762151@kernel.dk>
Date: Fri, 19 Nov 2010 11:41:25 -0800
Message-ID: <AANLkTimhArQ_NStZqxKcq-bzMWG3NpWK-N9+njdqfR0c@mail.gmail.com>
Subject: Re: [patch 14/28] fs: dcache scale subdirs
From: Tim Pepper <lnxninja@linux.vnet.ibm.com>
To: Nick Piggin <npiggin@kernel.dk>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2591
Lines: 70

On Tue, Nov 16, 2010 at 6:09 AM, Nick Piggin <npiggin@kernel.dk> wrote:

> Index: linux-2.6/fs/dcache.c
> ===================================================================
> --- linux-2.6.orig/fs/dcache.c ?2010-11-17 00:52:37.000000000 +1100
> +++ linux-2.6/fs/dcache.c ? ? ? 2010-11-17 01:05:44.000000000 +1100

> @@ -217,24 +219,22 @@ static void dentry_lru_move_tail(struct
> ?*
> ?* If this is the root of the dentry tree, return NULL.
> ?*
> - * dcache_lock and d_lock must be held by caller, are dropped by d_kill.
> + * dcache_lock and d_lock and d_parent->d_lock must be held by caller, and
> + * are dropped by d_kill.
> ?*/
> -static struct dentry *d_kill(struct dentry *dentry)
> +static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
> ? ? ? ?__releases(dentry->d_lock)
> + ? ? ? __releases(parent->d_lock)
> ? ? ? ?__releases(dcache_lock)
> ?{
> - ? ? ? struct dentry *parent;
> -
> ? ? ? ?list_del(&dentry->d_u.d_child);
> + ? ? ? if (parent)
> + ? ? ? ? ? ? ? spin_unlock(&parent->d_lock);
> ? ? ? ?dentry_iput(dentry);
> ? ? ? ?/*
> ? ? ? ? * dentry_iput drops the locks, at which point nobody (except
> ? ? ? ? * transient RCU lookups) can reach this dentry.
> ? ? ? ? */
> - ? ? ? if (IS_ROOT(dentry))
> - ? ? ? ? ? ? ? parent = NULL;
> - ? ? ? else
> - ? ? ? ? ? ? ? parent = dentry->d_parent;
> ? ? ? ?d_free(dentry);
> ? ? ? ?return parent;
> ?}
> @@ -270,6 +270,7 @@ static struct dentry *d_kill(struct dent
>
> ?void dput(struct dentry *dentry)
> ?{
> + ? ? ? struct dentry *parent;
> ? ? ? ?if (!dentry)
> ? ? ? ? ? ? ? ?return;
>
> @@ -277,6 +278,10 @@ void dput(struct dentry *dentry)
> ? ? ? ?if (dentry->d_count == 1)
> ? ? ? ? ? ? ? ?might_sleep();
> ? ? ? ?spin_lock(&dentry->d_lock);
> + ? ? ? if (IS_ROOT(dentry))
> + ? ? ? ? ? ? ? parent = NULL;
> + ? ? ? else
> + ? ? ? ? ? ? ? parent = dentry->d_parent;
> ? ? ? ?if (dentry->d_count == 1) {
> ? ? ? ? ? ? ? ?if (!spin_trylock(&dcache_lock)) {
> ? ? ? ? ? ? ? ? ? ? ? ?/*

Removed one and added three of the IS_ROOT() checks I think...Maybe
add a macro for setting the local parent pointer?  Ah never mind.  In
patch 28 they collapse back into a single instance.

In this patch the nested locking starts to feel a little more natural
to me.  The last number of patches in the series end up re-simplifying
a lot of intermediate complexity.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/