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From: Roman Gushchin To: Muchun Song Cc: Andrew Morton , linux-mm@kvack.org, Dave Chinner , linux-kernel@vger.kernel.org, Kent Overstreet , Hillf Danton , Christophe JAILLET Subject: Re: [PATCH v3 1/6] mm: memcontrol: introduce mem_cgroup_ino() and mem_cgroup_get_from_ino() Message-ID: References: <20220509183820.573666-1-roman.gushchin@linux.dev> <20220509183820.573666-2-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 22, 2022 at 03:05:33PM +0800, Muchun Song wrote: > On Mon, May 09, 2022 at 11:38:15AM -0700, Roman Gushchin wrote: > > Shrinker debugfs requires a way to represent memory cgroups without > > using full paths, both for displaying information and getting input > > from a user. > > > > Cgroup inode number is a perfect way, already used by bpf. > > > > This commit adds a couple of helper functions which will be used > > to handle memcg-aware shrinkers. > > > > Signed-off-by: Roman Gushchin > > --- > > include/linux/memcontrol.h | 21 +++++++++++++++++++++ > > mm/memcontrol.c | 23 +++++++++++++++++++++++ > > 2 files changed, 44 insertions(+) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index fe580cb96683..a6de9e5c1549 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -831,6 +831,15 @@ static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg) > > } > > struct mem_cgroup *mem_cgroup_from_id(unsigned short id); > > > > +#ifdef CONFIG_SHRINKER_DEBUG > > +static inline unsigned long mem_cgroup_ino(struct mem_cgroup *memcg) > > +{ > > + return memcg ? cgroup_ino(memcg->css.cgroup) : 0; > > +} > > + > > +struct mem_cgroup *mem_cgroup_get_from_ino(unsigned long ino); > > +#endif > > + > > static inline struct mem_cgroup *mem_cgroup_from_seq(struct seq_file *m) > > { > > return mem_cgroup_from_css(seq_css(m)); > > @@ -1324,6 +1333,18 @@ static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id) > > return NULL; > > } > > > > +#ifdef CONFIG_SHRINKER_DEBUG > > +static inline unsigned long mem_cgroup_ino(struct mem_cgroup *memcg) > > +{ > > + return 0; > > +} > > + > > +static inline struct mem_cgroup *mem_cgroup_get_from_ino(unsigned long ino) > > +{ > > + return NULL; > > +} > > +#endif > > + > > static inline struct mem_cgroup *mem_cgroup_from_seq(struct seq_file *m) > > { > > return NULL; > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 04cea4fa362a..e6472728fa66 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -5018,6 +5018,29 @@ struct mem_cgroup *mem_cgroup_from_id(unsigned short id) > > return idr_find(&mem_cgroup_idr, id); > > } > > > > +#ifdef CONFIG_SHRINKER_DEBUG > > +struct mem_cgroup *mem_cgroup_get_from_ino(unsigned long ino) > > +{ > > + struct cgroup *cgrp; > > + struct cgroup_subsys_state *css; > > + struct mem_cgroup *memcg; > > + > > + cgrp = cgroup_get_from_id(ino); > > + if (!cgrp) > > + return ERR_PTR(-ENOENT); > > + > > + css = cgroup_get_e_css(cgrp, &memory_cgrp_subsys); > > + if (css) > > + memcg = container_of(css, struct mem_cgroup, css); > > + else > > + memcg = ERR_PTR(-ENOENT); > > + > > + cgroup_put(cgrp); > > I think it's better to use css_put() here since the refcount is get > via cgroup_get_e_css() which returns a css struct. cgroup_put() is matching cgroup_get_from_id(). The reference grabbed by cgroup_get_e_css() shouldn't be dropped because mem_cgroup_get_from_ino() has a "get" semantics. Thanks!