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radix-tree: add support for multi-order iterating

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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>
This commit is contained in:
Ross Zwisler 2016-05-20 17:02:26 -07:00 • committed by Linus Torvalds
parent 7b60e9ad59
commit 21ef533931
4 changed files with 102 additions and 41 deletions
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66
lib/radix-tree.c
View file

@ -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) {