radix-tree: add support for multi-order iterating

This enables the macros radix_tree_for_each_slot() and friends to be
used with multi-order entries.

The way that this works is that we treat all entries in a given slots[]
array as a single chunk.  If the index given to radix_tree_next_chunk()
happens to point us to a sibling entry, we will back up iter->index so
that it points to the canonical entry, and that will be the place where
we start our iteration.

As we're processing a chunk in radix_tree_next_slot(), we process
canonical entries, skip over sibling entries, and restart the chunk
lookup if we find a non-sibling indirect pointer.  This drops back to
the radix_tree_next_chunk() code, which will re-walk the tree and look
for another chunk.

This allows us to properly handle multi-order entries mixed with other
entries that are at various heights in the radix tree.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index e1512a6..8558d52 100644 (file)
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -330,8 +330,9 @@ static inline void radix_tree_preload_end(void)
  * struct radix_tree_iter - radix tree iterator state
  *
  * @index:     index of current slot
- * @next_index:        next-to-last index for this chunk
+ * @next_index:        one beyond the last index for this chunk
  * @tags:      bit-mask for tag-iterating
+ * @shift:     shift for the node that holds our slots
  *
  * This radix tree iterator works in terms of "chunks" of slots.  A chunk is a
  * subinterval of slots contained within one radix tree leaf node.  It is
@@ -344,8 +345,20 @@ struct radix_tree_iter {
        unsigned long   index;
        unsigned long   next_index;
        unsigned long   tags;
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+       unsigned int    shift;
+#endif
 };
 
+static inline unsigned int iter_shift(struct radix_tree_iter *iter)
+{
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+       return iter->shift;
+#else
+       return 0;
+#endif
+}
+
 #define RADIX_TREE_ITER_TAG_MASK       0x00FF  /* tag index in lower byte */
 #define RADIX_TREE_ITER_TAGGED         0x0100  /* lookup tagged slots */
 #define RADIX_TREE_ITER_CONTIG         0x0200  /* stop at first hole */
@@ -405,6 +418,12 @@ void **radix_tree_iter_retry(struct radix_tree_iter *iter)
        return NULL;
 }
 
+static inline unsigned long
+__radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
+{
+       return iter->index + (slots << iter_shift(iter));
+}
+
 /**
  * radix_tree_iter_next - resume iterating when the chunk may be invalid
  * @iter:      iterator state
@@ -416,7 +435,7 @@ void **radix_tree_iter_retry(struct radix_tree_iter *iter)
 static inline __must_check
 void **radix_tree_iter_next(struct radix_tree_iter *iter)
 {
-       iter->next_index = iter->index + 1;
+       iter->next_index = __radix_tree_iter_add(iter, 1);
        iter->tags = 0;
        return NULL;
 }
@@ -430,7 +449,12 @@ void **radix_tree_iter_next(struct radix_tree_iter *iter)
 static __always_inline long
 radix_tree_chunk_size(struct radix_tree_iter *iter)
 {
-       return iter->next_index - iter->index;
+       return (iter->next_index - iter->index) >> iter_shift(iter);
+}
+
+static inline void *indirect_to_ptr(void *ptr)
+{
+       return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
 }
 
 /**
@@ -448,24 +472,51 @@ static __always_inline void **
 radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags)
 {
        if (flags & RADIX_TREE_ITER_TAGGED) {
+               void *canon = slot;
+
                iter->tags >>= 1;
+               if (unlikely(!iter->tags))
+                       return NULL;
+               while (IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
+                                       radix_tree_is_indirect_ptr(slot[1])) {
+                       if (indirect_to_ptr(slot[1]) == canon) {
+                               iter->tags >>= 1;
+                               iter->index = __radix_tree_iter_add(iter, 1);
+                               slot++;
+                               continue;
+                       }
+                       iter->next_index = __radix_tree_iter_add(iter, 1);
+                       return NULL;
+               }
                if (likely(iter->tags & 1ul)) {
-                       iter->index++;
+                       iter->index = __radix_tree_iter_add(iter, 1);
                        return slot + 1;
                }
-               if (!(flags & RADIX_TREE_ITER_CONTIG) && likely(iter->tags)) {
+               if (!(flags & RADIX_TREE_ITER_CONTIG)) {
                        unsigned offset = __ffs(iter->tags);
 
                        iter->tags >>= offset;
-                       iter->index += offset + 1;
+                       iter->index = __radix_tree_iter_add(iter, offset + 1);
                        return slot + offset + 1;
                }
        } else {
-               long size = radix_tree_chunk_size(iter);
+               long count = radix_tree_chunk_size(iter);
+               void *canon = slot;
 
-               while (--size > 0) {
+               while (--count > 0) {
                        slot++;
-                       iter->index++;
+                       iter->index = __radix_tree_iter_add(iter, 1);
+
+                       if (IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
+                           radix_tree_is_indirect_ptr(*slot)) {
+                               if (indirect_to_ptr(*slot) == canon)
+                                       continue;
+                               else {
+                                       iter->next_index = iter->index;
+                                       break;
+                               }
+                       }
+
                        if (likely(*slot))
                                return slot;
                        if (flags & RADIX_TREE_ITER_CONTIG) {

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index ff46042..a4da86e 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -75,11 +75,6 @@ static inline void *ptr_to_indirect(void *ptr)
        return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
 }
 
-static inline void *indirect_to_ptr(void *ptr)
-{
-       return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
-}
-
 #define RADIX_TREE_RETRY       ptr_to_indirect(NULL)
 
 #ifdef CONFIG_RADIX_TREE_MULTIORDER
@@ -885,6 +880,14 @@ int radix_tree_tag_get(struct radix_tree_root *root,
 }
 EXPORT_SYMBOL(radix_tree_tag_get);
 
+static inline void __set_iter_shift(struct radix_tree_iter *iter,
+                                       unsigned int shift)
+{
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+       iter->shift = shift;
+#endif
+}
+
 /**
  * radix_tree_next_chunk - find next chunk of slots for iteration
  *
@@ -898,7 +901,7 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
 {
        unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
        struct radix_tree_node *rnode, *node;
-       unsigned long index, offset, height;
+       unsigned long index, offset, maxindex;
 
        if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
                return NULL;
@@ -916,33 +919,39 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
        if (!index && iter->index)
                return NULL;
 
-       rnode = rcu_dereference_raw(root->rnode);
+ restart:
+       shift = radix_tree_load_root(root, &rnode, &maxindex);
+       if (index > maxindex)
+               return NULL;
+
        if (radix_tree_is_indirect_ptr(rnode)) {
                rnode = indirect_to_ptr(rnode);
-       } else if (rnode && !index) {
+       } else if (rnode) {
                /* Single-slot tree */
-               iter->index = 0;
-               iter->next_index = 1;
+               iter->index = index;
+               iter->next_index = maxindex + 1;
                iter->tags = 1;
+               __set_iter_shift(iter, shift);
                return (void **)&root->rnode;
        } else
                return NULL;
 
-restart:
-       height = rnode->path & RADIX_TREE_HEIGHT_MASK;
-       shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+       shift -= RADIX_TREE_MAP_SHIFT;
        offset = index >> shift;
 
-       /* Index outside of the tree */
-       if (offset >= RADIX_TREE_MAP_SIZE)
-               return NULL;
-
        node = rnode;
        while (1) {
                struct radix_tree_node *slot;
+               unsigned new_off = radix_tree_descend(node, &slot, offset);
+
+               if (new_off < offset) {
+                       offset = new_off;
+                       index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
+                       index |= offset << shift;
+               }
+
                if ((flags & RADIX_TREE_ITER_TAGGED) ?
-                               !test_bit(offset, node->tags[tag]) :
-                               !node->slots[offset]) {
+                               !tag_get(node, tag, offset) : !slot) {
                        /* Hole detected */
                        if (flags & RADIX_TREE_ITER_CONTIG)
                                return NULL;
@@ -954,7 +963,10 @@ restart:
                                                offset + 1);
                        else
                                while (++offset < RADIX_TREE_MAP_SIZE) {
-                                       if (node->slots[offset])
+                                       void *slot = node->slots[offset];
+                                       if (is_sibling_entry(node, slot))
+                                               continue;
+                                       if (slot)
                                                break;
                                }
                        index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
@@ -964,25 +976,23 @@ restart:
                                return NULL;
                        if (offset == RADIX_TREE_MAP_SIZE)
                                goto restart;
+                       slot = rcu_dereference_raw(node->slots[offset]);
                }
 
-               /* This is leaf-node */
-               if (!shift)
-                       break;
-
-               slot = rcu_dereference_raw(node->slots[offset]);
-               if (slot == NULL)
+               if ((slot == NULL) || (slot == RADIX_TREE_RETRY))
                        goto restart;
                if (!radix_tree_is_indirect_ptr(slot))
                        break;
+
                node = indirect_to_ptr(slot);
                shift -= RADIX_TREE_MAP_SHIFT;
                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
        }
 
        /* Update the iterator state */
-       iter->index = index;
-       iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
+       iter->index = index & ~((1 << shift) - 1);
+       iter->next_index = (index | ((RADIX_TREE_MAP_SIZE << shift) - 1)) + 1;
+       __set_iter_shift(iter, shift);
 
        /* Construct iter->tags bit-mask from node->tags[tag] array */
        if (flags & RADIX_TREE_ITER_TAGGED) {

diff --git a/tools/testing/radix-tree/generated/autoconf.h b/tools/testing/radix-tree/generated/autoconf.h
new file mode 100644 (file)
index 0000000..ad18cf5
--- /dev/null
+++ b/tools/testing/radix-tree/generated/autoconf.h
@@ -0,0 +1,3 @@
+#define CONFIG_RADIX_TREE_MULTIORDER 1
+#define CONFIG_SHMEM 1
+#define CONFIG_SWAP 1

diff --git a/tools/testing/radix-tree/linux/kernel.h b/tools/testing/radix-tree/linux/kernel.h
index 8ea0ed4..be98a47 100644 (file)
--- a/tools/testing/radix-tree/linux/kernel.h
+++ b/tools/testing/radix-tree/linux/kernel.h
@@ -8,10 +8,7 @@
 #include <limits.h>
 
 #include "../../include/linux/compiler.h"
-
-#define CONFIG_RADIX_TREE_MULTIORDER
-#define CONFIG_SHMEM
-#define CONFIG_SWAP
+#include "../../../include/linux/kconfig.h"
 
 #define RADIX_TREE_MAP_SHIFT   3