percpu: allow limited allocation before slab is online
This patch updates percpu allocator such that it can serve limited
amount of allocation before slab comes online. This is primarily to
allow slab to depend on working percpu allocator.
Two parameters, PERCPU_DYNAMIC_EARLY_SIZE and SLOTS, determine how
much memory space and allocation map slots are reserved. If this
reserved area is exhausted, WARN_ON_ONCE() will trigger and allocation
will fail till slab comes online.
The following changes are made to implement early alloc.
* pcpu_mem_alloc() now checks slab_is_available()
* Chunks are allocated using pcpu_mem_alloc()
* Init paths make sure ai->dyn_size is at least as large as
PERCPU_DYNAMIC_EARLY_SIZE.
* Initial alloc maps are allocated in __initdata and copied to
kmalloc'd areas once slab is online.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 3ffd05e..b8b9084 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -45,6 +45,16 @@
#define PCPU_MIN_UNIT_SIZE PFN_ALIGN(64 << 10)
/*
+ * Percpu allocator can serve percpu allocations before slab is
+ * initialized which allows slab to depend on the percpu allocator.
+ * The following two parameters decide how much resource to
+ * preallocate for this. Keep PERCPU_DYNAMIC_RESERVE equal to or
+ * larger than PERCPU_DYNAMIC_EARLY_SIZE.
+ */
+#define PERCPU_DYNAMIC_EARLY_SLOTS 128
+#define PERCPU_DYNAMIC_EARLY_SIZE (12 << 10)
+
+/*
* PERCPU_DYNAMIC_RESERVE indicates the amount of free area to piggy
* back on the first chunk for dynamic percpu allocation if arch is
* manually allocating and mapping it for faster access (as a part of
@@ -135,6 +145,7 @@
#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
extern void __init setup_per_cpu_areas(void);
#endif
+extern void __init percpu_init_late(void);
#else /* CONFIG_SMP */
@@ -148,6 +159,8 @@
static inline void __init setup_per_cpu_areas(void) { }
+static inline void __init percpu_init_late(void) { }
+
static inline void *pcpu_lpage_remapped(void *kaddr)
{
return NULL;
diff --git a/init/main.c b/init/main.c
index 3bdb152..3ff8dd0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -522,6 +522,7 @@
page_cgroup_init_flatmem();
mem_init();
kmem_cache_init();
+ percpu_init_late();
pgtable_cache_init();
vmalloc_init();
}
diff --git a/mm/percpu.c b/mm/percpu.c
index c3e7010..e61dc2c 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -282,6 +282,9 @@
*/
static void *pcpu_mem_alloc(size_t size)
{
+ if (WARN_ON_ONCE(!slab_is_available()))
+ return NULL;
+
if (size <= PAGE_SIZE)
return kzalloc(size, GFP_KERNEL);
else {
@@ -392,13 +395,6 @@
old_size = chunk->map_alloc * sizeof(chunk->map[0]);
memcpy(new, chunk->map, old_size);
- /*
- * map_alloc < PCPU_DFL_MAP_ALLOC indicates that the chunk is
- * one of the first chunks and still using static map.
- */
- if (chunk->map_alloc >= PCPU_DFL_MAP_ALLOC)
- old = chunk->map;
-
chunk->map_alloc = new_alloc;
chunk->map = new;
new = NULL;
@@ -604,7 +600,7 @@
{
struct pcpu_chunk *chunk;
- chunk = kzalloc(pcpu_chunk_struct_size, GFP_KERNEL);
+ chunk = pcpu_mem_alloc(pcpu_chunk_struct_size);
if (!chunk)
return NULL;
@@ -1109,7 +1105,9 @@
memset(group_map, 0, sizeof(group_map));
memset(group_cnt, 0, sizeof(group_cnt));
- size_sum = PFN_ALIGN(static_size + reserved_size + dyn_size);
+ /* calculate size_sum and ensure dyn_size is enough for early alloc */
+ size_sum = PFN_ALIGN(static_size + reserved_size +
+ max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE));
dyn_size = size_sum - static_size - reserved_size;
/*
@@ -1338,7 +1336,8 @@
void *base_addr)
{
static char cpus_buf[4096] __initdata;
- static int smap[2], dmap[2];
+ static int smap[PERCPU_DYNAMIC_EARLY_SLOTS] __initdata;
+ static int dmap[PERCPU_DYNAMIC_EARLY_SLOTS] __initdata;
size_t dyn_size = ai->dyn_size;
size_t size_sum = ai->static_size + ai->reserved_size + dyn_size;
struct pcpu_chunk *schunk, *dchunk = NULL;
@@ -1361,14 +1360,13 @@
} while (0)
/* sanity checks */
- BUILD_BUG_ON(ARRAY_SIZE(smap) >= PCPU_DFL_MAP_ALLOC ||
- ARRAY_SIZE(dmap) >= PCPU_DFL_MAP_ALLOC);
PCPU_SETUP_BUG_ON(ai->nr_groups <= 0);
PCPU_SETUP_BUG_ON(!ai->static_size);
PCPU_SETUP_BUG_ON(!base_addr);
PCPU_SETUP_BUG_ON(ai->unit_size < size_sum);
PCPU_SETUP_BUG_ON(ai->unit_size & ~PAGE_MASK);
PCPU_SETUP_BUG_ON(ai->unit_size < PCPU_MIN_UNIT_SIZE);
+ PCPU_SETUP_BUG_ON(ai->dyn_size < PERCPU_DYNAMIC_EARLY_SIZE);
PCPU_SETUP_BUG_ON(pcpu_verify_alloc_info(ai) < 0);
/* process group information and build config tables accordingly */
@@ -1806,3 +1804,33 @@
__per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
}
#endif /* CONFIG_HAVE_SETUP_PER_CPU_AREA */
+
+/*
+ * First and reserved chunks are initialized with temporary allocation
+ * map in initdata so that they can be used before slab is online.
+ * This function is called after slab is brought up and replaces those
+ * with properly allocated maps.
+ */
+void __init percpu_init_late(void)
+{
+ struct pcpu_chunk *target_chunks[] =
+ { pcpu_first_chunk, pcpu_reserved_chunk, NULL };
+ struct pcpu_chunk *chunk;
+ unsigned long flags;
+ int i;
+
+ for (i = 0; (chunk = target_chunks[i]); i++) {
+ int *map;
+ const size_t size = PERCPU_DYNAMIC_EARLY_SLOTS * sizeof(map[0]);
+
+ BUILD_BUG_ON(size > PAGE_SIZE);
+
+ map = pcpu_mem_alloc(size);
+ BUG_ON(!map);
+
+ spin_lock_irqsave(&pcpu_lock, flags);
+ memcpy(map, chunk->map, size);
+ chunk->map = map;
+ spin_unlock_irqrestore(&pcpu_lock, flags);
+ }
+}