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t=1728084555; bh=aoLXUpmnj6nq/Dgd/ap+0tK44YWQD7Jz9lgBXXobjUM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XHaa71hytBhkcRCER9vhf4Q9rxZIjF9OQ5sO2kKHtj3OQ91zpf7NZ1aREWs/VSANr J7ZiQ2wcu/az1zTeuG+OCJxD+C2ARp5q//rA/l9QYtb2WCT7BegQQralN5a5nx+8ZD MK6WEV9uPYLtDIjEFqOmX2idf35dczSXUlgUQe5+rBe8X7yXVv+2h5P9fGNTq+3u8b 4Y/R87lEWp3wwNvtqofRIVE9j4tJOq67ykUylqukmZOm2Mq91BY1zP+/OKwWOn0bd0 ePOa9gxo3VvB7OGIo9qVmhR8ZJ3W/QTWdIZCkHWxPpbnakyi4OCISh1IR9zzLSocFN euzIafjVSmrCw== Date: Fri, 4 Oct 2024 16:29:12 -0700 From: Namhyung Kim To: Song Liu Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , LKML , bpf@vger.kernel.org, Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, Arnaldo Carvalho de Melo , Kees Cook Subject: Re: [PATCH v4 bpf-next 1/3] bpf: Add kmem_cache iterator Message-ID: References: <20241002180956.1781008-1-namhyung@kernel.org> <20241002180956.1781008-2-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: rpaa1fb3wjwapitxihrautqs95yxkueg X-Rspamd-Queue-Id: EE7104000D X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1728084555-946688 X-HE-Meta: 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 ZxoJRE52 OzaArSIjR/7ZUOdLQbCFmj/2NHPIY4IjWYtD1494Ftf97dxaFnRTMmjUwsCrZJcHCcNj/Oxadad9vzwfrnu0egSDFlxo+tPqNVCXoDaovN2J0fD1xp+Q8/eNnqMLpqr9rPoF8/fAWyGiW6Ly8J1ch3PznZIx5q0rgrTr9OsQLNkdqhm9X5fR8gkXNG5dj8BjBw85SiekcgbIw4oAe4uiMLivUWZZvyu6KldQmkJI5CMhobmux2GdOfd2XLM7AkGlo0tJ6Xg6Z5VcHGkk5Ake9YmLiuOf19fOp1ahS5CtTN3LrBtyLuJ7pvkFlYKJXTZiAkFaU33iIFdwe080atuA4EHBgMXCnfQjiZDqPD8/I6lt7547OCwK7mlnovOGVDCeMatgyMd+y7jpCRoXKPdDe9pQSuaZZM8hN9pd7 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 04, 2024 at 02:46:43PM -0700, Song Liu wrote: > On Fri, Oct 4, 2024 at 2:37 PM Namhyung Kim wrote: > > > > Hi Song, > > > > On Fri, Oct 04, 2024 at 01:33:19PM -0700, Song Liu wrote: > [...] > > > > + > > > > +static void *kmem_cache_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos) > > > > +{ > > > > + struct kmem_cache *s = v; > > > > + struct kmem_cache *next = NULL; > > > > + bool destroy = false; > > > > + > > > > + ++*pos; > > > > + > > > > + mutex_lock(&slab_mutex); > > > > + > > > > + if (list_last_entry(&slab_caches, struct kmem_cache, list) != s) { > > > > + next = list_next_entry(s, list); > > > > + if (next->refcount > 0) > > > > + next->refcount++; > > > > > > What if next->refcount <=0? Shall we find next of next? > > > > The slab_mutex should protect refcount == 0 case so it won't see that. > > The negative refcount means it's a boot_cache and we shouldn't touch the > > refcount. > > I see. Thanks for the explanation! > > Please add a comment here, and maybe also add > > WARN_ON_ONCE(next ->refcount == 0). Sure, thanks for your review! Namhyung