Received-SPF: pass (google.com: domain of linux-kernel+bounces-208865-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Message-ID: <ce62eb86-8539-4c7f-b929-926cec94e1f0@suse.cz>
Date: Mon, 10 Jun 2024 22:42:30 +0200
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH 05/14] tracefs: replace call_rcu by kfree_rcu for simple
 kmem_cache_free callback
Content-Language: en-US
To: paulmck@kernel.org, Steven Rostedt <rostedt@goodmis.org>
Cc: Julia Lawall <Julia.Lawall@inria.fr>, kernel-janitors@vger.kernel.org,
 Masami Hiramatsu <mhiramat@kernel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org
References: <20240609082726.32742-1-Julia.Lawall@inria.fr>
 <20240609082726.32742-6-Julia.Lawall@inria.fr>
 <20240610112223.151faf65@rorschach.local.home>
 <b647eacd-f6f3-4960-acfd-36c30f376995@paulmck-laptop>
From: Vlastimil Babka <vbabka@suse.cz>
Autocrypt: addr=vbabka@suse.cz; keydata=
 xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB
 KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB
 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+
 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy
 tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD
 Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4
 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc
 LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x
 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv
 BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg
 QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe
 AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ
 ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC
 Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87
 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ
 V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ
 PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ
 KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J
 Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm
 ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae
 h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl
 De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5
 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G
 /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB
 IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea
 X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2
 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ
 PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD
 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI
 EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr
 tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p
 eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX
 PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA
 HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj
 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED
 w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b
 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR
 EP+ylKVEKb0Q2A==
In-Reply-To: <b647eacd-f6f3-4960-acfd-36c30f376995@paulmck-laptop>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit

On 6/10/24 5:46 PM, Paul E. McKenney wrote:
> On Mon, Jun 10, 2024 at 11:22:23AM -0400, Steven Rostedt wrote:
>> On Sun,  9 Jun 2024 10:27:17 +0200
>> Julia Lawall <Julia.Lawall@inria.fr> wrote:
>> 
>> > diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
>> > index 7c29f4afc23d..338c52168e61 100644
>> > --- a/fs/tracefs/inode.c
>> > +++ b/fs/tracefs/inode.c
>> > @@ -53,14 +53,6 @@ static struct inode *tracefs_alloc_inode(struct super_block *sb)
>> >  	return &ti->vfs_inode;
>> >  }
>> >  
>> > -static void tracefs_free_inode_rcu(struct rcu_head *rcu)
>> > -{
>> > -	struct tracefs_inode *ti;
>> > -
>> > -	ti = container_of(rcu, struct tracefs_inode, rcu);
>> > -	kmem_cache_free(tracefs_inode_cachep, ti);
>> 
>> Does this work?
>> 
>> tracefs needs to be freed via the tracefs_inode_cachep. Does
>> kfree_rcu() handle specific frees for objects that were not allocated
>> via kmalloc()?
> 
> A recent change to kfree() allows it to correctly handle memory allocated
> via kmem_cache_alloc().  News to me as of a few weeks ago.  ;-)

Hey, I did try not to keep that a secret :)
https://lore.kernel.org/all/20230310103210.22372-8-vbabka@suse.cz/

> 							Thanx, Paul
> 
>> -- Steve
>> 
>> 
>> > -}
>> > -
>> >  static void tracefs_free_inode(struct inode *inode)
>> >  {
>> >  	struct tracefs_inode *ti = get_tracefs(inode);
>> > @@ -70,7 +62,7 @@ static void tracefs_free_inode(struct inode *inode)
>> >  	list_del_rcu(&ti->list);
>> >  	spin_unlock_irqrestore(&tracefs_inode_lock, flags);
>> >  
>> > -	call_rcu(&ti->rcu, tracefs_free_inode_rcu);
>> > +	kfree_rcu(ti, rcu);
>> >  }
>> >  
>> >  static ssize_t default_read_file(struct file *file, char __user *buf,
>>