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Sun, 26 Oct 2025 03:03:11 -0700 (PDT) From: Yafang Shao To: akpm@linux-foundation.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, david@redhat.com, lorenzo.stoakes@oracle.com Cc: 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, ziy@nvidia.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, clm@meta.com, bpf@vger.kernel.org, linux-mm@kvack.org, Yafang Shao Subject: [PATCH v12 mm-new 06/10] mm: bpf-thp: add support for global mode Date: Sun, 26 Oct 2025 18:01:55 +0800 Message-Id: <20251026100159.6103-7-laoar.shao@gmail.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20251026100159.6103-1-laoar.shao@gmail.com> References: <20251026100159.6103-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: kq181ck6gqw1qwkca3u7sdycgehrc5ip X-Rspamd-Queue-Id: 95C43120002 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1761472993-703087 X-HE-Meta: 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 6uTfsA2/ 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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 | 111 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 109 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory_bpf.c b/mm/huge_memory_bpf.c index f69c5851ea61..f8383c2a299f 100644 --- a/mm/huge_memory_bpf.c +++ b/mm/huge_memory_bpf.c @@ -35,6 +35,30 @@ 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) +{ + static struct bpf_thp_ops *bpf_thp; + int bpf_order; + + rcu_read_lock(); + bpf_thp = rcu_dereference(bpf_thp_global); + if (!bpf_thp || !bpf_thp->thp_get_order) + goto out; + + bpf_order = bpf_thp->thp_get_order(vma, type, orders); + if (bpf_order < 0) + goto out; + 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, @@ -47,6 +71,10 @@ 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) @@ -181,6 +209,23 @@ 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; @@ -191,6 +236,11 @@ 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; @@ -209,8 +259,10 @@ 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)) { err = -EBUSY; goto out; } @@ -226,12 +278,33 @@ 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); @@ -244,6 +317,31 @@ 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; @@ -251,6 +349,15 @@ 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