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Sun, 19 Oct 2025 20:17:18 -0700 (PDT) From: Yafang Shao To: akpm@linux-foundation.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, david@redhat.com, ziy@nvidia.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, willy@infradead.org, ameryhung@gmail.com, rientjes@google.com, corbet@lwn.net, 21cnbao@gmail.com, shakeel.butt@linux.dev, tj@kernel.org, lance.yang@linux.dev, rdunlap@infradead.org Cc: bpf@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Yafang Shao Subject: [PATCH v11 mm-new 06/10] mm: bpf-thp: add support for global mode Date: Mon, 20 Oct 2025 11:16:51 +0800 Message-Id: <20251020031655.1093-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20251020031655.1093-1-laoar.shao@gmail.com> References: <20251020031655.1093-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0C6204000B X-Stat-Signature: nx5oijts1dyf37gbepamspjup8sps3dt X-Rspam-User: X-HE-Tag: 1760930239-94024 X-HE-Meta: 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 i/CR1hTv 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 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: The per-process BPF-THP mode is unsuitable for managing shared resources such as shmem THP and file-backed THP. This aligns with known cgroup limitations for similar scenarios [0]. Introduce a global BPF-THP mode to address this gap. When registered: - All existing per-process instances are disabled - New per-process registrations are blocked - Existing per-process instances remain registered (no forced unregistration) The global mode takes precedence over per-process instances. Updates are type-isolated: global instances can only be updated by new global instances, and per-process instances by new per-process instances. Link: https://lore.kernel.org/linux-mm/YwNold0GMOappUxc@slm.duckdns.org/ [0] Signed-off-by: Yafang Shao --- mm/huge_memory_bpf.c | 109 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 107 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory_bpf.c b/mm/huge_memory_bpf.c index e8894c10d1d9..cad1ca6f59a4 100644 --- a/mm/huge_memory_bpf.c +++ b/mm/huge_memory_bpf.c @@ -33,6 +33,28 @@ struct bpf_thp_ops { }; static DEFINE_SPINLOCK(thp_ops_lock); +static struct bpf_thp_ops __rcu *bpf_thp_global; /* global mode */ + +static unsigned long +bpf_hook_thp_get_orders_global(struct vm_area_struct *vma, + enum tva_type type, + unsigned long orders) +{ + thp_order_fn_t *bpf_hook_thp_get_order; + int bpf_order; + + rcu_read_lock(); + bpf_hook_thp_get_order = rcu_dereference(bpf_thp_global->thp_get_order); + if (!bpf_hook_thp_get_order) + goto out; + + bpf_order = bpf_hook_thp_get_order(vma, type, orders); + orders &= BIT(bpf_order); + +out: + rcu_read_unlock(); + return orders; +} unsigned long bpf_hook_thp_get_orders(struct vm_area_struct *vma, enum tva_type type, @@ -45,6 +67,10 @@ unsigned long bpf_hook_thp_get_orders(struct vm_area_struct *vma, if (!mm) return orders; + /* Global BPF-THP takes precedence over per-process BPF-THP. */ + if (rcu_access_pointer(bpf_thp_global)) + return bpf_hook_thp_get_orders_global(vma, type, orders); + rcu_read_lock(); bpf_thp = rcu_dereference(mm->bpf_mm.bpf_thp); if (!bpf_thp || !bpf_thp->thp_get_order) @@ -177,6 +203,23 @@ static int bpf_thp_init_member(const struct btf_type *t, return 0; } +static int bpf_thp_reg_gloabl(void *kdata, struct bpf_link *link) +{ + struct bpf_thp_ops *ops = kdata; + + /* Protect the global pointer bpf_thp_global from concurrent writes. */ + spin_lock(&thp_ops_lock); + /* Only one instance is allowed. */ + if (rcu_access_pointer(bpf_thp_global)) { + spin_unlock(&thp_ops_lock); + return -EBUSY; + } + + rcu_assign_pointer(bpf_thp_global, ops); + spin_unlock(&thp_ops_lock); + return 0; +} + static int bpf_thp_reg(void *kdata, struct bpf_link *link) { struct bpf_thp_ops *bpf_thp = kdata; @@ -187,6 +230,11 @@ static int bpf_thp_reg(void *kdata, struct bpf_link *link) pid_t pid; pid = bpf_thp->pid; + + /* Fallback to global mode if pid is not set. */ + if (!pid) + return bpf_thp_reg_gloabl(kdata, link); + p = find_get_task_by_vpid(pid); if (!p) return -ESRCH; @@ -207,8 +255,10 @@ static int bpf_thp_reg(void *kdata, struct bpf_link *link) * might register this task simultaneously. */ spin_lock(&thp_ops_lock); - /* Each process is exclusively managed by a single BPF-THP. */ - if (rcu_access_pointer(mm->bpf_mm.bpf_thp)) + /* Each process is exclusively managed by a single BPF-THP. + * Global mode disables per-process instances. + */ + if (rcu_access_pointer(mm->bpf_mm.bpf_thp) || rcu_access_pointer(bpf_thp_global)) goto out_lock; err = 0; rcu_assign_pointer(mm->bpf_mm.bpf_thp, bpf_thp); @@ -224,12 +274,33 @@ static int bpf_thp_reg(void *kdata, struct bpf_link *link) return err; } +static void bpf_thp_unreg_global(void *kdata, struct bpf_link *link) +{ + struct bpf_thp_ops *bpf_thp; + + spin_lock(&thp_ops_lock); + if (!rcu_access_pointer(bpf_thp_global)) { + spin_unlock(&thp_ops_lock); + return; + } + + bpf_thp = rcu_replace_pointer(bpf_thp_global, NULL, + lockdep_is_held(&thp_ops_lock)); + WARN_ON_ONCE(!bpf_thp); + spin_unlock(&thp_ops_lock); + + synchronize_rcu(); +} + static void bpf_thp_unreg(void *kdata, struct bpf_link *link) { struct bpf_thp_ops *bpf_thp = kdata; struct bpf_mm_ops *bpf_mm; struct list_head *pos, *n; + if (!bpf_thp->pid) + return bpf_thp_unreg_global(kdata, link); + spin_lock(&thp_ops_lock); list_for_each_safe(pos, n, &bpf_thp->mm_list) { bpf_mm = list_entry(pos, struct bpf_mm_ops, bpf_thp_list); @@ -242,6 +313,31 @@ static void bpf_thp_unreg(void *kdata, struct bpf_link *link) synchronize_rcu(); } +static int bpf_thp_update_global(void *kdata, void *old_kdata, struct bpf_link *link) +{ + struct bpf_thp_ops *old_bpf_thp = old_kdata; + struct bpf_thp_ops *bpf_thp = kdata; + struct bpf_thp_ops *old_global; + + if (!old_bpf_thp || !bpf_thp) + return -EINVAL; + + spin_lock(&thp_ops_lock); + /* BPF-THP global instance has already been removed. */ + if (!rcu_access_pointer(bpf_thp_global)) { + spin_unlock(&thp_ops_lock); + return -ENOENT; + } + + old_global = rcu_replace_pointer(bpf_thp_global, bpf_thp, + lockdep_is_held(&thp_ops_lock)); + WARN_ON_ONCE(!old_global); + spin_unlock(&thp_ops_lock); + + synchronize_rcu(); + return 0; +} + static int bpf_thp_update(void *kdata, void *old_kdata, struct bpf_link *link) { struct bpf_thp_ops *old_bpf_thp = old_kdata; @@ -249,6 +345,15 @@ static int bpf_thp_update(void *kdata, void *old_kdata, struct bpf_link *link) struct bpf_mm_ops *bpf_mm; struct list_head *pos, *n; + /* Updates are confined to instances of the same scope: + * global to global, process-local to process-local. + */ + if (!!old_bpf_thp->pid != !!bpf_thp->pid) + return -EINVAL; + + if (!old_bpf_thp->pid) + return bpf_thp_update_global(kdata, old_kdata, link); + INIT_LIST_HEAD(&bpf_thp->mm_list); /* Could be optimized to a per-instance lock if this lock becomes a bottleneck. */ -- 2.47.3