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xarray: Replace exceptional entries

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Introduce xarray value entries and tagged pointers to replace radix
tree exceptional entries.  This is a slight change in encoding to allow
the use of an extra bit (we can now store BITS_PER_LONG - 1 bits in a
value entry).  It is also a change in emphasis; exceptional entries are
intimidating and different.  As the comment explains, you can choose
to store values or pointers in the xarray and they are both first-class
citizens.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
This commit is contained in:
Matthew Wilcox 2017-11-03 13:30:42 -04:00
parent 66ee620f06
commit 3159f943aa
26 changed files with 278 additions and 232 deletions
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21
lib/radix-tree.c
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@ -340,14 +340,12 @@ static void dump_ida_node(void *entry, unsigned long index)
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++)
dump_ida_node(node->slots[i],
index | (i << node->shift));
} else if (radix_tree_exceptional_entry(entry)) {
} else if (xa_is_value(entry)) {
pr_debug("ida excp: %p offset %d indices %lu-%lu data %lx\n",
entry, (int)(index & RADIX_TREE_MAP_MASK),
index * IDA_BITMAP_BITS,
index * IDA_BITMAP_BITS + BITS_PER_LONG -
RADIX_TREE_EXCEPTIONAL_SHIFT,
(unsigned long)entry >>
RADIX_TREE_EXCEPTIONAL_SHIFT);
index * IDA_BITMAP_BITS + BITS_PER_XA_VALUE,
xa_to_value(entry));
} else {
struct ida_bitmap *bitmap = entry;
@ -656,7 +654,7 @@ static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
BUG_ON(shift > BITS_PER_LONG);
if (radix_tree_is_internal_node(entry)) {
entry_to_node(entry)->parent = node;
} else if (radix_tree_exceptional_entry(entry)) {
} else if (xa_is_value(entry)) {
/* Moving an exceptional root->rnode to a node */
node->exceptional = 1;
}
@ -955,12 +953,12 @@ static inline int insert_entries(struct radix_tree_node *node,
!is_sibling_entry(node, old) &&
(old != RADIX_TREE_RETRY))
radix_tree_free_nodes(old);
if (radix_tree_exceptional_entry(old))
if (xa_is_value(old))
node->exceptional--;
}
if (node) {
node->count += n;
if (radix_tree_exceptional_entry(item))
if (xa_is_value(item))
node->exceptional += n;
}
return n;
@ -974,7 +972,7 @@ static inline int insert_entries(struct radix_tree_node *node,
rcu_assign_pointer(*slot, item);
if (node) {
node->count++;
if (radix_tree_exceptional_entry(item))
if (xa_is_value(item))
node->exceptional++;
}
return 1;
@ -1190,8 +1188,7 @@ void __radix_tree_replace(struct radix_tree_root *root,
radix_tree_update_node_t update_node)
{
void *old = rcu_dereference_raw(*slot);
int exceptional = !!radix_tree_exceptional_entry(item) -
!!radix_tree_exceptional_entry(old);
int exceptional = !!xa_is_value(item) - !!xa_is_value(old);
int count = calculate_count(root, node, slot, item, old);
/*
@ -1992,7 +1989,7 @@ static bool __radix_tree_delete(struct radix_tree_root *root,
struct radix_tree_node *node, void __rcu **slot)
{
void *old = rcu_dereference_raw(*slot);
int exceptional = radix_tree_exceptional_entry(old) ? -1 : 0;
int exceptional = xa_is_value(old) ? -1 : 0;
unsigned offset = get_slot_offset(node, slot);
int tag;