1 files changed, 116 insertions, 33 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
index d9e6e5d..9ac0198 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -48,8 +48,8 @@
  * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
  *   regular address to percpu pointer and back
  *
- * - use pcpu_setup_static() during percpu area initialization to
- *   setup kernel static percpu area
+ * - use pcpu_setup_first_chunk() during percpu area initialization to
+ *   setup the first chunk containing the kernel static percpu area
  */
 
 #include <linux/bitmap.h>
@@ -67,7 +67,6 @@
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
-#define PCPU_MIN_UNIT_PAGES		16	/* max alloc size in pages */
 #define PCPU_SLOT_BASE_SHIFT		5	/* 1-31 shares the same slot */
 #define PCPU_DFL_MAP_ALLOC		16	/* start a map with 16 ents */
 
@@ -80,6 +79,7 @@ struct pcpu_chunk {
 	int			map_used;	/* # of map entries used */
 	int			map_alloc;	/* # of map entries allocated */
 	int			*map;		/* allocation map */
+	bool			immutable;	/* no [de]population allowed */
 	struct page		*page[];	/* #cpus * UNIT_PAGES */
 };
 
@@ -521,6 +521,9 @@ static void pcpu_unmap(struct pcpu_chunk *chunk, int page_start, int page_end,
 	unsigned int last = num_possible_cpus() - 1;
 	unsigned int cpu;
 
+	/* unmap must not be done on immutable chunk */
+	WARN_ON(chunk->immutable);
+
 	/*
 	 * Each flushing trial can be very expensive, issue flush on
 	 * the whole region at once rather than doing it for each cpu.
@@ -602,6 +605,9 @@ static int pcpu_map(struct pcpu_chunk *chunk, int page_start, int page_end)
 	unsigned int cpu;
 	int err;
 
+	/* map must not be done on immutable chunk */
+	WARN_ON(chunk->immutable);
+
 	for_each_possible_cpu(cpu) {
 		err = map_kernel_range_noflush(
 				pcpu_chunk_addr(chunk, cpu, page_start),
@@ -727,8 +733,7 @@ void *__alloc_percpu(size_t size, size_t align)
 	struct pcpu_chunk *chunk;
 	int slot, off;
 
-	if (unlikely(!size || size > PCPU_MIN_UNIT_PAGES * PAGE_SIZE ||
-		     align > PAGE_SIZE)) {
+	if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) {
 		WARN(true, "illegal size (%zu) or align (%zu) for "
 		     "percpu allocation\n", size, align);
 		return NULL;
@@ -776,6 +781,7 @@ EXPORT_SYMBOL_GPL(__alloc_percpu);
 
 static void pcpu_kill_chunk(struct pcpu_chunk *chunk)
 {
+	WARN_ON(chunk->immutable);
 	pcpu_depopulate_chunk(chunk, 0, pcpu_unit_size, false);
 	list_del(&chunk->list);
 	rb_erase(&chunk->rb_node, &pcpu_addr_root);
@@ -821,33 +827,73 @@ void free_percpu(void *ptr)
 EXPORT_SYMBOL_GPL(free_percpu);
 
 /**
- * pcpu_setup_static - initialize kernel static percpu area
- * @populate_pte_fn: callback to allocate pagetable
- * @pages: num_possible_cpus() * PFN_UP(cpu_size) pages
- * @cpu_size: the size of static percpu area in bytes
- *
- * Initialize kernel static percpu area.  The caller should allocate
- * all the necessary pages and pass them in @pages.
- * @populate_pte_fn() is called on each page to be used for percpu
- * mapping and is responsible for making sure all the necessary page
- * tables for the page is allocated.
+ * pcpu_setup_first_chunk - initialize the first percpu chunk
+ * @get_page_fn: callback to fetch page pointer
+ * @static_size: the size of static percpu area in bytes
+ * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, 0 for auto
+ * @free_size: free size in bytes, 0 for auto
+ * @base_addr: mapped address, NULL for auto
+ * @populate_pte_fn: callback to allocate pagetable, NULL if unnecessary
+ *
+ * Initialize the first percpu chunk which contains the kernel static
+ * perpcu area.  This function is to be called from arch percpu area
+ * setup path.  The first two parameters are mandatory.  The rest are
+ * optional.
+ *
+ * @get_page_fn() should return pointer to percpu page given cpu
+ * number and page number.  It should at least return enough pages to
+ * cover the static area.  The returned pages for static area should
+ * have been initialized with valid data.  If @unit_size is specified,
+ * it can also return pages after the static area.  NULL return
+ * indicates end of pages for the cpu.  Note that @get_page_fn() must
+ * return the same number of pages for all cpus.
+ *
+ * @unit_size, if non-zero, determines unit size and must be aligned
+ * to PAGE_SIZE and equal to or larger than @static_size + @free_size.
+ *
+ * @free_size determines the number of free bytes after the static
+ * area in the first chunk.  If zero, whatever left is available.
+ * Specifying non-zero value make percpu leave the area after
+ * @static_size + @free_size alone.
+ *
+ * Non-null @base_addr means that the caller already allocated virtual
+ * region for the first chunk and mapped it.  percpu must not mess
+ * with the chunk.  Note that @base_addr with 0 @unit_size or non-NULL
+ * @populate_pte_fn doesn't make any sense.
+ *
+ * @populate_pte_fn is used to populate the pagetable.  NULL means the
+ * caller already populated the pagetable.
  *
  * RETURNS:
  * The determined pcpu_unit_size which can be used to initialize
  * percpu access.
  */
-size_t __init pcpu_setup_static(pcpu_populate_pte_fn_t populate_pte_fn,
-				struct page **pages, size_t cpu_size)
+size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
+				     size_t static_size, size_t unit_size,
+				     size_t free_size, void *base_addr,
+				     pcpu_populate_pte_fn_t populate_pte_fn)
 {
 	static struct vm_struct static_vm;
 	struct pcpu_chunk *static_chunk;
-	int nr_cpu_pages = DIV_ROUND_UP(cpu_size, PAGE_SIZE);
 	unsigned int cpu;
+	int nr_pages;
 	int err, i;
 
-	pcpu_unit_pages = max_t(int, PCPU_MIN_UNIT_PAGES, PFN_UP(cpu_size));
+	/* santiy checks */
+	BUG_ON(!static_size);
+	BUG_ON(!unit_size && free_size);
+	BUG_ON(unit_size && unit_size < static_size + free_size);
+	BUG_ON(unit_size & ~PAGE_MASK);
+	BUG_ON(base_addr && !unit_size);
+	BUG_ON(base_addr && populate_pte_fn);
 
-	pcpu_static_size = cpu_size;
+	if (unit_size)
+		pcpu_unit_pages = unit_size >> PAGE_SHIFT;
+	else
+		pcpu_unit_pages = max_t(int, PCPU_MIN_UNIT_SIZE >> PAGE_SHIFT,
+					PFN_UP(static_size));
+
+	pcpu_static_size = static_size;
 	pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
 	pcpu_chunk_size = num_possible_cpus() * pcpu_unit_size;
 	pcpu_chunk_struct_size = sizeof(struct pcpu_chunk)
@@ -862,29 +908,66 @@ size_t __init pcpu_setup_static(pcpu_populate_pte_fn_t populate_pte_fn,
 	for (i = 0; i < pcpu_nr_slots; i++)
 		INIT_LIST_HEAD(&pcpu_slot[i]);
 
-	/* init and register vm area */
-	static_vm.flags = VM_ALLOC;
-	static_vm.size = pcpu_chunk_size;
-	vm_area_register_early(&static_vm, PAGE_SIZE);
-
 	/* init static_chunk */
 	static_chunk = alloc_bootmem(pcpu_chunk_struct_size);
 	INIT_LIST_HEAD(&static_chunk->list);
 	static_chunk->vm = &static_vm;
-	static_chunk->free_size = pcpu_unit_size - pcpu_static_size;
+
+	if (free_size)
+		static_chunk->free_size = free_size;
+	else
+		static_chunk->free_size = pcpu_unit_size - pcpu_static_size;
+
 	static_chunk->contig_hint = static_chunk->free_size;
 
-	/* assign pages and map them */
+	/* allocate vm address */
+	static_vm.flags = VM_ALLOC;
+	static_vm.size = pcpu_chunk_size;
+
+	if (!base_addr)
+		vm_area_register_early(&static_vm, PAGE_SIZE);
+	else {
+		/*
+		 * Pages already mapped.  No need to remap into
+		 * vmalloc area.  In this case the static chunk can't
+		 * be mapped or unmapped by percpu and is marked
+		 * immutable.
+		 */
+		static_vm.addr = base_addr;
+		static_chunk->immutable = true;
+	}
+
+	/* assign pages */
+	nr_pages = -1;
 	for_each_possible_cpu(cpu) {
-		for (i = 0; i < nr_cpu_pages; i++) {
-			*pcpu_chunk_pagep(static_chunk, cpu, i) = *pages++;
-			populate_pte_fn(pcpu_chunk_addr(static_chunk, cpu, i));
+		for (i = 0; i < pcpu_unit_pages; i++) {
+			struct page *page = get_page_fn(cpu, i);
+
+			if (!page)
+				break;
+			*pcpu_chunk_pagep(static_chunk, cpu, i) = page;
 		}
+
+		BUG_ON(i < PFN_UP(pcpu_static_size));
+
+		if (nr_pages < 0)
+			nr_pages = i;
+		else
+			BUG_ON(nr_pages != i);
 	}
 
-	err = pcpu_map(static_chunk, 0, nr_cpu_pages);
-	if (err)
-		panic("failed to setup static percpu area, err=%d\n", err);
+	/* map them */
+	if (populate_pte_fn) {
+		for_each_possible_cpu(cpu)
+			for (i = 0; i < nr_pages; i++)
+				populate_pte_fn(pcpu_chunk_addr(static_chunk,
+								cpu, i));
+
+		err = pcpu_map(static_chunk, 0, nr_pages);
+		if (err)
+			panic("failed to setup static percpu area, err=%d\n",
+			      err);
+	}
 
 	/* link static_chunk in */
 	pcpu_chunk_relocate(static_chunk, -1);