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    Subject[PATCH rfc 2/5] mm: memcontrol: introduce mem_cgroup_ino() and mem_cgroup_get_from_ino()
    Date
    Shrinker sysfs requires a way to represent memory cgroups without
    using full paths, both for displaying information and getting input
    from a user.

    Cgroup inode numbers is a perfect way, used by e.g. bpf.

    This commit adds a couple of helper functions, which will be used to
    represent and interact with memcg-aware shrinkers using shrinkers sysfs.

    Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
    ---
    include/linux/memcontrol.h | 9 +++++++++
    mm/memcontrol.c | 23 +++++++++++++++++++++++
    2 files changed, 32 insertions(+)

    diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
    index cc16ba262464..299472046000 100644
    --- a/include/linux/memcontrol.h
    +++ b/include/linux/memcontrol.h
    @@ -838,6 +838,15 @@ 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 cgroup_ino(memcg->css.cgroup);
    +}
    +
    +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));
    diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    index 4a3e1300c5a1..030dd637ec7a 100644
    --- a/mm/memcontrol.c
    +++ b/mm/memcontrol.c
    @@ -5023,6 +5023,29 @@ 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);
    +
    + return memcg;
    +}
    +#endif
    +
    static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
    {
    struct mem_cgroup_per_node *pn;
    --
    2.35.1
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