Merge branch 'percpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'percpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  percpu: remove rbtree and use page->index instead
  percpu: don't put the first chunk in reverse-map rbtree

1 files changed, 44 insertions, 97 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
index 1aa5d8fbca12..c0b2c1a76e81 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -23,7 +23,7 @@
  * Allocation is done in offset-size areas of single unit space.  Ie,
  * an area of 512 bytes at 6k in c1 occupies 512 bytes at 6k of c1:u0,
  * c1:u1, c1:u2 and c1:u3.  Percpu access can be done by configuring
- * percpu base registers UNIT_SIZE apart.
+ * percpu base registers pcpu_unit_size apart.
  *
  * There are usually many small percpu allocations many of them as
  * small as 4 bytes.  The allocator organizes chunks into lists
@@ -38,8 +38,8 @@
  * region and negative allocated.  Allocation inside a chunk is done
  * by scanning this map sequentially and serving the first matching
  * entry.  This is mostly copied from the percpu_modalloc() allocator.
- * Chunks are also linked into a rb tree to ease address to chunk
- * mapping during free.
+ * Chunks can be determined from the address using the index field
+ * in the page struct. The index field contains a pointer to the chunk.
  *
  * To use this allocator, arch code should do the followings.
  *
@@ -61,7 +61,6 @@
 #include <linux/mutex.h>
 #include <linux/percpu.h>
 #include <linux/pfn.h>
-#include <linux/rbtree.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/vmalloc.h>
@@ -88,7 +87,6 @@
 
 struct pcpu_chunk {
         struct list_head        list;           /* linked to pcpu_slot lists */
-        struct rb_node          rb_node;        /* key is chunk->vm->addr */
         int                     free_size;      /* free bytes in the chunk */
         int                     contig_hint;    /* max contiguous size hint */
         struct vm_struct        *vm;            /* mapped vmalloc region */
@@ -110,9 +108,21 @@ static size_t pcpu_chunk_struct_size __read_mostly;
 void *pcpu_base_addr __read_mostly;
 EXPORT_SYMBOL_GPL(pcpu_base_addr);
 
-/* optional reserved chunk, only accessible for reserved allocations */
+/*
+ * The first chunk which always exists.  Note that unlike other
+ * chunks, this one can be allocated and mapped in several different
+ * ways and thus often doesn't live in the vmalloc area.
+ */
+static struct pcpu_chunk *pcpu_first_chunk;
+
+/*
+ * Optional reserved chunk.  This chunk reserves part of the first
+ * chunk and serves it for reserved allocations.  The amount of
+ * reserved offset is in pcpu_reserved_chunk_limit.  When reserved
+ * area doesn't exist, the following variables contain NULL and 0
+ * respectively.
+ */
 static struct pcpu_chunk *pcpu_reserved_chunk;
-/* offset limit of the reserved chunk */
 static int pcpu_reserved_chunk_limit;
 
 /*
@@ -121,7 +131,7 @@ static int pcpu_reserved_chunk_limit;
  * There are two locks - pcpu_alloc_mutex and pcpu_lock.  The former
  * protects allocation/reclaim paths, chunks and chunk->page arrays.
  * The latter is a spinlock and protects the index data structures -
- * chunk slots, rbtree, chunks and area maps in chunks.
+ * chunk slots, chunks and area maps in chunks.
  *
  * During allocation, pcpu_alloc_mutex is kept locked all the time and
  * pcpu_lock is grabbed and released as necessary.  All actual memory
@@ -140,7 +150,6 @@ static DEFINE_MUTEX(pcpu_alloc_mutex);	/* protects whole alloc and reclaim */
 static DEFINE_SPINLOCK(pcpu_lock);      /* protects index data structures */
 
 static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */
-static struct rb_root pcpu_addr_root = RB_ROOT; /* chunks by address */
 
 /* reclaim work to release fully free chunks, scheduled from free path */
 static void pcpu_reclaim(struct work_struct *work);
@@ -191,6 +200,18 @@ static bool pcpu_chunk_page_occupied(struct pcpu_chunk *chunk,
         return *pcpu_chunk_pagep(chunk, 0, page_idx) != NULL;
 }
 
+/* set the pointer to a chunk in a page struct */
+static void pcpu_set_page_chunk(struct page *page, struct pcpu_chunk *pcpu)
+{
+        page->index = (unsigned long)pcpu;
+}
+
+/* obtain pointer to a chunk from a page struct */
+static struct pcpu_chunk *pcpu_get_page_chunk(struct page *page)
+{
+        return (struct pcpu_chunk *)page->index;
+}
+
 /**
  * pcpu_mem_alloc - allocate memory
  * @size: bytes to allocate
@@ -257,93 +278,26 @@ static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
         }
 }
 
-static struct rb_node **pcpu_chunk_rb_search(void *addr,
-                                             struct rb_node **parentp)
-{
-        struct rb_node **p = &pcpu_addr_root.rb_node;
-        struct rb_node *parent = NULL;
-        struct pcpu_chunk *chunk;
-
-        while (*p) {
-                parent = *p;
-                chunk = rb_entry(parent, struct pcpu_chunk, rb_node);
-
-                if (addr < chunk->vm->addr)
-                        p = &(*p)->rb_left;
-                else if (addr > chunk->vm->addr)
-                        p = &(*p)->rb_right;
-                else
-                        break;
-        }
-
-        if (parentp)
-                *parentp = parent;
-        return p;
-}
-
 /**
- * pcpu_chunk_addr_search - search for chunk containing specified address
- * @addr: address to search for
- *
- * Look for chunk which might contain @addr.  More specifically, it
- * searchs for the chunk with the highest start address which isn't
- * beyond @addr.
- *
- * CONTEXT:
- * pcpu_lock.
+ * pcpu_chunk_addr_search - determine chunk containing specified address
+ * @addr: address for which the chunk needs to be determined.
  *
  * RETURNS:
  * The address of the found chunk.
  */
 static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
 {
-        struct rb_node *n, *parent;
-        struct pcpu_chunk *chunk;
+        void *first_start = pcpu_first_chunk->vm->addr;
 
-        /* is it in the reserved chunk? */
-        if (pcpu_reserved_chunk) {
-                void *start = pcpu_reserved_chunk->vm->addr;
-
-                if (addr >= start && addr < start + pcpu_reserved_chunk_limit)
+        /* is it in the first chunk? */
+        if (addr >= first_start && addr < first_start + pcpu_chunk_size) {
+                /* is it in the reserved area? */
+                if (addr < first_start + pcpu_reserved_chunk_limit)
                         return pcpu_reserved_chunk;
+                return pcpu_first_chunk;
         }
 
-        /* nah... search the regular ones */
-        n = *pcpu_chunk_rb_search(addr, &parent);
-        if (!n) {
-                /* no exactly matching chunk, the parent is the closest */
-                n = parent;
-                BUG_ON(!n);
-        }
-        chunk = rb_entry(n, struct pcpu_chunk, rb_node);
-
-        if (addr < chunk->vm->addr) {
-                /* the parent was the next one, look for the previous one */
-                n = rb_prev(n);
-                BUG_ON(!n);
-                chunk = rb_entry(n, struct pcpu_chunk, rb_node);
-        }
-
-        return chunk;
-}
-
-/**
- * pcpu_chunk_addr_insert - insert chunk into address rb tree
- * @new: chunk to insert
- *
- * Insert @new into address rb tree.
- *
- * CONTEXT:
- * pcpu_lock.
- */
-static void pcpu_chunk_addr_insert(struct pcpu_chunk *new)
-{
-        struct rb_node **p, *parent;
-
-        p = pcpu_chunk_rb_search(new->vm->addr, &parent);
-        BUG_ON(*p);
-        rb_link_node(&new->rb_node, parent, p);
-        rb_insert_color(&new->rb_node, &pcpu_addr_root);
+        return pcpu_get_page_chunk(vmalloc_to_page(addr));
 }
 
 /**
@@ -755,6 +709,7 @@ static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
                                                   alloc_mask, 0);
                         if (!*pagep)
                                 goto err;
+                        pcpu_set_page_chunk(*pagep, chunk);
                 }
         }
 
@@ -879,7 +834,6 @@ restart:
 
         spin_lock_irq(&pcpu_lock);
         pcpu_chunk_relocate(chunk, -1);
-        pcpu_chunk_addr_insert(chunk);
         goto restart;
 
 area_found:
@@ -968,7 +922,6 @@ static void pcpu_reclaim(struct work_struct *work)
                 if (chunk == list_first_entry(head, struct pcpu_chunk, list))
                         continue;
 
-                rb_erase(&chunk->rb_node, &pcpu_addr_root);
                 list_move(&chunk->list, &todo);
         }
 
@@ -1147,7 +1100,8 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
 
         if (reserved_size) {
                 schunk->free_size = reserved_size;
-                pcpu_reserved_chunk = schunk;   /* not for dynamic alloc */
+                pcpu_reserved_chunk = schunk;
+                pcpu_reserved_chunk_limit = static_size + reserved_size;
         } else {
                 schunk->free_size = dyn_size;
                 dyn_size = 0;                   /* dynamic area covered */
@@ -1158,8 +1112,6 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
         if (schunk->free_size)
                 schunk->map[schunk->map_used++] = schunk->free_size;
 
-        pcpu_reserved_chunk_limit = static_size + schunk->free_size;
-
         /* init dynamic chunk if necessary */
         if (dyn_size) {
                 dchunk = alloc_bootmem(sizeof(struct pcpu_chunk));
@@ -1226,13 +1178,8 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
         }
 
         /* link the first chunk in */
-        if (!dchunk) {
-                pcpu_chunk_relocate(schunk, -1);
-                pcpu_chunk_addr_insert(schunk);
-        } else {
-                pcpu_chunk_relocate(dchunk, -1);
-                pcpu_chunk_addr_insert(dchunk);
-        }
+        pcpu_first_chunk = dchunk ?: schunk;
+        pcpu_chunk_relocate(pcpu_first_chunk, -1);
 
         /* we're done */
         pcpu_base_addr = (void *)pcpu_chunk_addr(schunk, 0, 0);