percpu: simplify pcpu_setup_first_chunk()

Now that all first chunk allocator helpers allocate and map the first
chunk themselves, there's no need to have optional default alloc/map
in pcpu_setup_first_chunk().  Drop @populate_pte_fn and only leave
@dyn_size optional and make all other params mandatory.

This makes it much easier to follow what pcpu_setup_first_chunk() is
doing and what actual differences tweaking each parameter results in.

[ Impact: drop unused code path ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>

1 files changed, 30 insertions, 74 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
index 17db527ee2e2..21d938a10662 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -983,24 +983,22 @@ EXPORT_SYMBOL_GPL(free_percpu);
  * 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
- * @reserved_size: the size of reserved percpu area in bytes
+ * @reserved_size: the size of reserved percpu area in bytes, 0 for none
  * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
- * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE, -1 for auto
- * @base_addr: mapped address, NULL for auto
- * @populate_pte_fn: callback to allocate pagetable, NULL if unnecessary
+ * @unit_size: unit size in bytes, must be multiple of PAGE_SIZE
+ * @base_addr: mapped address
  *
  * 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.
+ * setup path.
  *
  * @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.
+ * have been initialized with valid data.  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.
  *
  * @reserved_size, if non-zero, specifies the amount of bytes to
  * reserve after the static area in the first chunk.  This reserves
@@ -1015,17 +1013,12 @@ EXPORT_SYMBOL_GPL(free_percpu);
  * non-negative value makes percpu leave alone the area beyond
  * @static_size + @reserved_size + @dyn_size.
  *
- * @unit_size, if non-negative, specifies unit size and must be
- * aligned to PAGE_SIZE and equal to or larger than @static_size +
- * @reserved_size + if non-negative, @dyn_size.
- *
- * 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.
+ * @unit_size specifies unit size and must be aligned to PAGE_SIZE and
+ * equal to or larger than @static_size + @reserved_size + if
+ * non-negative, @dyn_size.
  *
- * @populate_pte_fn is used to populate the pagetable.  NULL means the
- * caller already populated the pagetable.
+ * The caller should have mapped the first chunk at @base_addr and
+ * copied static data to each unit.
  *
  * If the first chunk ends up with both reserved and dynamic areas, it
  * is served by two chunks - one to serve the core static and reserved
@@ -1040,9 +1033,8 @@ EXPORT_SYMBOL_GPL(free_percpu);
  */
 size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
                                      size_t static_size, size_t reserved_size,
-                                     ssize_t dyn_size, ssize_t unit_size,
-                                     void *base_addr,
-                                     pcpu_fc_populate_pte_fn_t populate_pte_fn)
+                                     ssize_t dyn_size, size_t unit_size,
+                                     void *base_addr)
 {
         static struct vm_struct first_vm;
         static int smap[2], dmap[2];
@@ -1050,27 +1042,18 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
                           (dyn_size >= 0 ? dyn_size : 0);
         struct pcpu_chunk *schunk, *dchunk = NULL;
         unsigned int cpu;
-        int nr_pages;
-        int err, i;
+        int i, nr_pages;
 
         /* santiy checks */
         BUILD_BUG_ON(ARRAY_SIZE(smap) >= PCPU_DFL_MAP_ALLOC ||
                      ARRAY_SIZE(dmap) >= PCPU_DFL_MAP_ALLOC);
         BUG_ON(!static_size);
-        if (unit_size >= 0) {
-                BUG_ON(unit_size < size_sum);
-                BUG_ON(unit_size & ~PAGE_MASK);
-                BUG_ON(unit_size < PCPU_MIN_UNIT_SIZE);
-        } else
-                BUG_ON(base_addr);
-        BUG_ON(base_addr && populate_pte_fn);
-
-        if (unit_size >= 0)
-                pcpu_unit_pages = unit_size >> PAGE_SHIFT;
-        else
-                pcpu_unit_pages = max_t(int, PCPU_MIN_UNIT_SIZE >> PAGE_SHIFT,
-                                        PFN_UP(size_sum));
+        BUG_ON(!base_addr);
+        BUG_ON(unit_size < size_sum);
+        BUG_ON(unit_size & ~PAGE_MASK);
+        BUG_ON(unit_size < PCPU_MIN_UNIT_SIZE);
 
+        pcpu_unit_pages = unit_size >> PAGE_SHIFT;
         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)
@@ -1079,6 +1062,10 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
         if (dyn_size < 0)
                 dyn_size = pcpu_unit_size - static_size - reserved_size;
 
+        first_vm.flags = VM_ALLOC;
+        first_vm.size = pcpu_chunk_size;
+        first_vm.addr = base_addr;
+
         /*
          * Allocate chunk slots.  The additional last slot is for
          * empty chunks.
@@ -1101,6 +1088,7 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
         schunk->map = smap;
         schunk->map_alloc = ARRAY_SIZE(smap);
         schunk->page = schunk->page_ar;
+        schunk->immutable = true;
 
         if (reserved_size) {
                 schunk->free_size = reserved_size;
@@ -1124,31 +1112,13 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
                 dchunk->map = dmap;
                 dchunk->map_alloc = ARRAY_SIZE(dmap);
                 dchunk->page = schunk->page_ar; /* share page map with schunk */
+                dchunk->immutable = true;
 
                 dchunk->contig_hint = dchunk->free_size = dyn_size;
                 dchunk->map[dchunk->map_used++] = -pcpu_reserved_chunk_limit;
                 dchunk->map[dchunk->map_used++] = dchunk->free_size;
         }
 
-        /* allocate vm address */
-        first_vm.flags = VM_ALLOC;
-        first_vm.size = pcpu_chunk_size;
-
-        if (!base_addr)
-                vm_area_register_early(&first_vm, PAGE_SIZE);
-        else {
-                /*
-                 * Pages already mapped.  No need to remap into
-                 * vmalloc area.  In this case the first chunks can't
-                 * be mapped or unmapped by percpu and are marked
-                 * immutable.
-                 */
-                first_vm.addr = base_addr;
-                schunk->immutable = true;
-                if (dchunk)
-                        dchunk->immutable = true;
-        }
-
         /* assign pages */
         nr_pages = -1;
         for_each_possible_cpu(cpu) {
@@ -1168,19 +1138,6 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
                         BUG_ON(nr_pages != i);
         }
 
-        /* map them */
-        if (populate_pte_fn) {
-                for_each_possible_cpu(cpu)
-                        for (i = 0; i < nr_pages; i++)
-                                populate_pte_fn(pcpu_chunk_addr(schunk,
-                                                                cpu, i));
-
-                err = pcpu_map(schunk, 0, nr_pages);
-                if (err)
-                        panic("failed to setup static percpu area, err=%d\n",
-                              err);
-        }
-
         /* link the first chunk in */
         pcpu_first_chunk = dchunk ?: schunk;
         pcpu_chunk_relocate(pcpu_first_chunk, -1);
@@ -1282,7 +1239,7 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 
         return pcpu_setup_first_chunk(pcpue_get_page, static_size,
                                       reserved_size, dyn_size,
-                                      pcpue_unit_size, pcpue_ptr, NULL);
+                                      pcpue_unit_size, pcpue_ptr);
 }
 
 /*
@@ -1387,8 +1344,7 @@ ssize_t __init pcpu_4k_first_chunk(size_t static_size, size_t reserved_size,
 
         ret = pcpu_setup_first_chunk(pcpu4k_get_page, static_size,
                                      reserved_size, -1,
-                                     pcpu4k_unit_pages << PAGE_SHIFT, vm.addr,
-                                     NULL);
+                                     pcpu4k_unit_pages << PAGE_SHIFT, vm.addr);
         goto out_free_ar;
 
 enomem:
@@ -1521,7 +1477,7 @@ ssize_t __init pcpu_lpage_first_chunk(size_t static_size, size_t reserved_size,
 
         ret = pcpu_setup_first_chunk(pcpul_get_page, static_size,
                                      reserved_size, dyn_size, pcpul_unit_size,
-                                     pcpul_vm.addr, NULL);
+                                     pcpul_vm.addr);
 
         /* sort pcpul_map array for pcpu_lpage_remapped() */
         for (i = 0; i < num_possible_cpus() - 1; i++)