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Mon, 28 Sep 2026 08:16:15 +0000 X-Mizu-Trace-ID: ef3d12d70e3ed8e3 X-Migadu-Flow: FLOW_OUT From: Ye Liu Date: Mon, 28 Sep 2026 16:15:55 +0800 Subject: [PATCH v4 2/2] mm/vmalloc: fix vmalloc_dump_obj cross-zone VA lookup MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260928-vmalloc_dump_obj-v4-2-6f288a431edc@linux.dev> References: <20260928-vmalloc_dump_obj-v4-0-6f288a431edc@linux.dev> In-Reply-To: <20260928-vmalloc_dump_obj-v4-0-6f288a431edc@linux.dev> To: Andrew Morton , Uladzislau Rezki , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Ye Liu X-Mailer: b4 0.14.3 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 696AF40006 X-Stat-Signature: xpas8q6hporg1tb9saeyzgw8w7z9j4ex X-HE-Tag: 1790583377-347735 X-HE-Meta: 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 Y9tP6bIt h1fG02WA1pXVPxI20vjsYLHXM1gVNPfEFTUs7RD8mMS0Oh9C7ri7s0OqZ6UbEl1lO/IppaBtCrDopIGdtCyk1wZ+n5bBwElJTQrt440U7eOLuyzbf1ZhnDPqm4grnKVwP2jxLjeDALl/OC9DSFo4RZ8L84vCxqNoOLpQ3aLwpskqHHpSym40N5otZo4dMMfSC1rd7VRKeFFn20D/AcnnLTiPuMhAK2OrDih7PD1dZPfVyP9FTSQR2cwIH/WAOISpW2E/0HmlUIJqrKK2jJWjDMCdzRIgrh4prpFl0 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Ye Liu vmalloc_dump_obj() searches only one vmap node (addr_to_node(addr)), but a vmalloc allocation may span multiple vmap zones. The VA is stored in only one node's rb-tree (addr_to_node(va_start)), so an object pointer in a different zone than va_start maps to a different node and the search misses. This affects any allocation larger than vmap_zone_size (64 KiB) on multi-CPU systems. Extract find_vmap_area_lock() from find_vmap_area() to share the cross-node iteration logic. The helper supports both spin_lock and spin_trylock, the latter for atomic dump contexts (OOM, KASAN, RCU). Signed-off-by: Ye Liu --- mm/vmalloc.c | 108 ++++++++++++++++++++++++++++++++++++----------------------- 1 file changed, 66 insertions(+), 42 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index df42d8a6f058..4f4d7453962f 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2517,67 +2517,94 @@ static void free_unmap_vmap_area(struct vmap_area *va) free_vmap_area_noflush(va); } -struct vmap_area *find_vmap_area(unsigned long addr) +static inline int next_vmap_node_id(int i) +{ + return (i + nr_vmap_nodes - 1) % nr_vmap_nodes; +} + +enum vmap_lock_mode { + VMAP_LOCK, + VMAP_TRYLOCK, +}; + +/* + * Search for a vmap_area at @addr across all vmap nodes. An + * addr_to_node_id(addr) converts an address to a node index where + * a VA is located. If VA spans several zones and passed addr is not + * the same as va->va_start, what is not common, we may need to scan + * extra nodes. See an example: + * + * <----va----> + * -|-----|-----|-----|-----|- + * 1 2 0 1 + * + * VA resides in node 1 whereas it spans 1, 2 an 0. If passed addr + * is within 2 or 0 nodes we should do extra work. + * + * Returns the VA with @locked_vn->busy.lock held; the caller must + * release it. If @mode is VMAP_TRYLOCK, nodes that cannot be locked + * are skipped. + */ +static struct vmap_area * +find_vmap_area_lock(unsigned long addr, struct vmap_node **locked_vn, + enum vmap_lock_mode mode) { struct vmap_node *vn; struct vmap_area *va; int i, j; + *locked_vn = NULL; + if (unlikely(!vmap_initialized)) return NULL; - /* - * An addr_to_node_id(addr) converts an address to a node index - * where a VA is located. If VA spans several zones and passed - * addr is not the same as va->va_start, what is not common, we - * may need to scan extra nodes. See an example: - * - * <----va----> - * -|-----|-----|-----|-----|- - * 1 2 0 1 - * - * VA resides in node 1 whereas it spans 1, 2 an 0. If passed - * addr is within 2 or 0 nodes we should do extra work. - */ i = j = addr_to_node_id(addr); do { vn = &vmap_nodes[i]; - spin_lock(&vn->busy.lock); - va = __find_vmap_area(addr, &vn->busy.root); - spin_unlock(&vn->busy.lock); + if (mode == VMAP_LOCK) { + spin_lock(&vn->busy.lock); + } else { + if (!spin_trylock(&vn->busy.lock)) + continue; + } - if (va) + va = __find_vmap_area(addr, &vn->busy.root); + if (va) { + *locked_vn = vn; return va; - } while ((i = (i + nr_vmap_nodes - 1) % nr_vmap_nodes) != j); + } + + spin_unlock(&vn->busy.lock); + } while ((i = next_vmap_node_id(i)) != j); return NULL; } -static struct vmap_area *find_unlink_vmap_area(unsigned long addr) +struct vmap_area *find_vmap_area(unsigned long addr) { struct vmap_node *vn; struct vmap_area *va; - int i, j; - - /* - * Check the comment in the find_vmap_area() about the loop. - */ - i = j = addr_to_node_id(addr); - do { - vn = &vmap_nodes[i]; - spin_lock(&vn->busy.lock); - va = __find_vmap_area(addr, &vn->busy.root); - if (va) - unlink_va(va, &vn->busy.root); + va = find_vmap_area_lock(addr, &vn, VMAP_LOCK); + if (va) spin_unlock(&vn->busy.lock); - if (va) - return va; - } while ((i = (i + nr_vmap_nodes - 1) % nr_vmap_nodes) != j); + return va; +} - return NULL; +static struct vmap_area *find_unlink_vmap_area(unsigned long addr) +{ + struct vmap_node *vn; + struct vmap_area *va; + + va = find_vmap_area_lock(addr, &vn, VMAP_LOCK); + if (va) { + unlink_va(va, &vn->busy.root); + spin_unlock(&vn->busy.lock); + } + + return va; } /*** Per cpu kva allocator ***/ @@ -5278,14 +5305,11 @@ bool vmalloc_dump_obj(void *object) unsigned long nr_pages; addr = PAGE_ALIGN_DOWN((unsigned long) object); - vn = addr_to_node(addr); - - if (!spin_trylock(&vn->busy.lock)) - return false; - va = __find_vmap_area(addr, &vn->busy.root); + va = find_vmap_area_lock(addr, &vn, VMAP_TRYLOCK); if (!va || !va->vm) { - spin_unlock(&vn->busy.lock); + if (va) + spin_unlock(&vn->busy.lock); return false; } -- 2.25.1