[PATCH 32/62] ida: Convert to using xarray

Matthew Wilcox
2017-11-22T21:18:22Z

Use the xarray infrstructure like we used the radix tree infrastructure.
This lets us get rid of idr_get_free() from the radix tree code.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
include/linux/idr.h | 8 +-
include/linux/radix-tree.h | 4 -
lib/idr.c | 239 +++++++++++++++++++++++----------------------
lib/radix-tree.c | 86 +---------------
4 files changed, 128 insertions(+), 209 deletions(-)

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 57945eb0792a..8f62f7ba79fd 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -170,11 +170,11 @@ struct ida_bitmap {
DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);

struct ida {
- struct radix_tree_root ida_rt;
+ struct xarray idxa;
};

#define IDA_INIT(name) { \
- .ida_rt = RADIX_TREE_INIT(name, IDR_INIT_FLAGS | GFP_NOWAIT), \
+ .idxa = __XARRAY_INIT(name.idxa, IDR_INIT_FLAGS) \
}
#define DEFINE_IDA(name) struct ida name = IDA_INIT(name)

@@ -189,7 +189,7 @@ void ida_simple_remove(struct ida *ida, unsigned int id);

static inline void ida_init(struct ida *ida)
{
- INIT_RADIX_TREE(&ida->ida_rt, IDR_INIT_FLAGS | GFP_NOWAIT);
+ __xa_init(&ida->idxa, IDR_INIT_FLAGS);
}

/**
@@ -206,6 +206,6 @@ static inline int ida_get_new(struct ida *ida, int *p_id)

static inline bool ida_is_empty(const struct ida *ida)
{
- return radix_tree_empty(&ida->ida_rt);
+ return xa_empty(&ida->idxa);
}
#endif /* _LINUX_IDR_H */
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 1da1fb01e993..3e1c7ef06a0b 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -310,10 +310,6 @@ int radix_tree_split(struct radix_tree_root *, unsigned long index,
int radix_tree_join(struct radix_tree_root *, unsigned long index,
unsigned new_order, void *);

-void __rcu **idr_get_free(struct radix_tree_root *root,
- struct radix_tree_iter *iter, gfp_t gfp,
- unsigned long max);
-
enum {
RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */
RADIX_TREE_ITER_TAGGED = 0x10, /* lookup tagged slots */
diff --git a/lib/idr.c b/lib/idr.c
index 713b19e6f1b3..574dcade0c4b 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -6,7 +6,6 @@
#include <linux/xarray.h>

DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
-static DEFINE_SPINLOCK(simple_ida_lock);

/* In radix-tree.c temporarily */
extern bool idr_nomem(struct xa_state *, gfp_t);
@@ -277,104 +276,114 @@ EXPORT_SYMBOL_GPL(idr_replace);

#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS - 1)

+static struct ida_bitmap *alloc_ida_bitmap(void)
+{
+ struct ida_bitmap *bitmap = this_cpu_xchg(ida_bitmap, NULL);
+ if (bitmap)
+ memset(bitmap, 0, sizeof(*bitmap));
+ return bitmap;
+}
+
+static void free_ida_bitmap(struct ida_bitmap *bitmap)
+{
+ if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
+ kfree(bitmap);
+}
+
/**
* ida_get_new_above - allocate new ID above or equal to a start id
* @ida: ida handle
* @start: id to start search at
* @id: pointer to the allocated handle
*
- * Allocate new ID above or equal to @start. It should be called
- * with any required locks to ensure that concurrent calls to
- * ida_get_new_above() / ida_get_new() / ida_remove() are not allowed.
- * Consider using ida_simple_get() if you do not have complex locking
- * requirements.
+ * Allocate new ID above or equal to @start. The ida has its own lock,
+ * although you may wish to provide your own locking around it.
*
* If memory is required, it will return %-EAGAIN, you should unlock
* and go back to the ida_pre_get() call. If the ida is full, it will
* return %-ENOSPC. On success, it will return 0.
*
- * @id returns a value in the range @start ... %0x7fffffff.
+ * @id returns a value in the range @start ... %INT_MAX.
*/
int ida_get_new_above(struct ida *ida, int start, int *id)
{
- struct radix_tree_root *root = &ida->ida_rt;
- void __rcu **slot;
- struct radix_tree_iter iter;
+ unsigned long flags;
+ unsigned long index = start / IDA_BITMAP_BITS;
+ unsigned int bit = start % IDA_BITMAP_BITS;
+ XA_STATE(xas, index);
struct ida_bitmap *bitmap;
- unsigned long index;
- unsigned bit;
- int new;
-
- index = start / IDA_BITMAP_BITS;
- bit = start % IDA_BITMAP_BITS;
-
- slot = radix_tree_iter_init(&iter, index);
- for (;;) {
- if (slot)
- slot = radix_tree_next_slot(slot, &iter,
- RADIX_TREE_ITER_TAGGED);
- if (!slot) {
- slot = idr_get_free(root, &iter, GFP_NOWAIT, IDA_MAX);
- if (IS_ERR(slot)) {
- if (slot == ERR_PTR(-ENOMEM))
- return -EAGAIN;
- return PTR_ERR(slot);
- }
- }
- if (iter.index > index)
- bit = 0;
- new = iter.index * IDA_BITMAP_BITS;
- bitmap = rcu_dereference_raw(*slot);
- if (xa_is_value(bitmap)) {
- unsigned long tmp = xa_to_value(bitmap);
- int vbit = find_next_zero_bit(&tmp, BITS_PER_XA_VALUE,
- bit);
- if (vbit < BITS_PER_XA_VALUE) {
- tmp |= 1UL << vbit;
- rcu_assign_pointer(*slot, xa_mk_value(tmp));
- *id = new + vbit;
- return 0;
- }
- bitmap = this_cpu_xchg(ida_bitmap, NULL);
- if (!bitmap)
- return -EAGAIN;
- memset(bitmap, 0, sizeof(*bitmap));
- bitmap->bitmap[0] = tmp;
- rcu_assign_pointer(*slot, bitmap);
- }
+ unsigned int new;
+
+ xa_lock_irqsave(&ida->idxa, flags);
+retry:
+ bitmap = xas_find_tag(&ida->idxa, &xas, IDA_MAX, XA_FREE_TAG);
+ if (xas.xa_index > IDA_MAX)
+ goto nospc;
+ if (xas.xa_index > index)
+ bit = 0;
+ new = xas.xa_index * IDA_BITMAP_BITS;
+ if (xa_is_value(bitmap)) {
+ unsigned long value = xa_to_value(bitmap);
+ if (bit < BITS_PER_XA_VALUE) {
+ unsigned long tmp = value | ((1UL << bit) - 1);
+ bit = ffz(tmp);

- if (bitmap) {
- bit = find_next_zero_bit(bitmap->bitmap,
- IDA_BITMAP_BITS, bit);
- new += bit;
- if (new < 0)
- return -ENOSPC;
- if (bit == IDA_BITMAP_BITS)
- continue;
-
- __set_bit(bit, bitmap->bitmap);
- if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
- radix_tree_iter_tag_clear(root, &iter,
- XA_FREE_TAG);
- } else {
- new += bit;
- if (new < 0)
- return -ENOSPC;
if (bit < BITS_PER_XA_VALUE) {
- bitmap = xa_mk_value(1UL << bit);
- } else {
- bitmap = this_cpu_xchg(ida_bitmap, NULL);
- if (!bitmap)
- return -EAGAIN;
- memset(bitmap, 0, sizeof(*bitmap));
- __set_bit(bit, bitmap->bitmap);
+ value |= (1UL << bit);
+ xas_store(&ida->idxa, &xas, xa_mk_value(value));
+ new += bit;
+ goto unlock;
}
- radix_tree_iter_replace(root, &iter, slot, bitmap);
}

- *id = new;
- return 0;
+ bitmap = alloc_ida_bitmap();
+ if (!bitmap)
+ goto nomem;
+ bitmap->bitmap[0] = value;
+ new += bit;
+ __set_bit(bit, bitmap->bitmap);
+ xas_store(&ida->idxa, &xas, bitmap);
+ if (xas_error(&xas))
+ free_ida_bitmap(bitmap);
+ } else if (bitmap) {
+ bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit);
+ if (bit == IDA_BITMAP_BITS)
+ goto retry;
+ new += bit;
+ if (new > INT_MAX)
+ goto nospc;
+ __set_bit(bit, bitmap->bitmap);
+ if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
+ xas_clear_tag(&ida->idxa, &xas, XA_FREE_TAG);
+ } else if (bit < BITS_PER_XA_VALUE) {
+ new += bit;
+ bitmap = xa_mk_value(1UL << bit);
+ xas_store(&ida->idxa, &xas, bitmap);
+ } else {
+ bitmap = alloc_ida_bitmap();
+ if (!bitmap)
+ goto nomem;
+ new += bit;
+ __set_bit(bit, bitmap->bitmap);
+ xas_store(&ida->idxa, &xas, bitmap);
+ if (xas_error(&xas))
+ free_ida_bitmap(bitmap);
}
+
+ if (idr_nomem(&xas, GFP_NOWAIT))
+ goto retry;
+unlock:
+ xa_unlock_irqrestore(&ida->idxa, flags);
+ if (xas_error(&xas) == -ENOMEM)
+ return -EAGAIN;
+ *id = new;
+ return 0;
+nospc:
+ xa_unlock_irqrestore(&ida->idxa, flags);
+ return -ENOSPC;
+nomem:
+ xa_unlock_irqrestore(&ida->idxa, flags);
+ return -EAGAIN;
}
EXPORT_SYMBOL(ida_get_new_above);

@@ -382,45 +391,44 @@ EXPORT_SYMBOL(ida_get_new_above);
* ida_remove - Free the given ID
* @ida: ida handle
* @id: ID to free
- *
- * This function should not be called at the same time as ida_get_new_above().
*/
void ida_remove(struct ida *ida, int id)
{
+ unsigned long flags;
unsigned long index = id / IDA_BITMAP_BITS;
- unsigned offset = id % IDA_BITMAP_BITS;
+ unsigned bit = id % IDA_BITMAP_BITS;
+ XA_STATE(xas, index);
struct ida_bitmap *bitmap;
- unsigned long *btmp;
- struct radix_tree_iter iter;
- void __rcu **slot;

- slot = radix_tree_iter_lookup(&ida->ida_rt, &iter, index);
- if (!slot)
+ xa_lock_irqsave(&ida->idxa, flags);
+ bitmap = xas_load(&ida->idxa, &xas);
+ if (!bitmap)
goto err;
-
- bitmap = rcu_dereference_raw(*slot);
if (xa_is_value(bitmap)) {
- btmp = (unsigned long *)slot;
- offset += 1; /* Intimate knowledge of the xa_data encoding */
- if (offset >= BITS_PER_LONG)
+ unsigned long v = xa_to_value(bitmap);
+ if (bit >= BITS_PER_XA_VALUE)
goto err;
+ if (!(v & (1UL << bit)))
+ goto err;
+ v &= ~(1UL << bit);
+ if (v)
+ bitmap = xa_mk_value(v);
+ else
+ bitmap = NULL;
+ xas_store(&ida->idxa, &xas, bitmap);
} else {
- btmp = bitmap->bitmap;
- }
- if (!test_bit(offset, btmp))
- goto err;
-
- __clear_bit(offset, btmp);
- radix_tree_iter_tag_set(&ida->ida_rt, &iter, XA_FREE_TAG);
- if (xa_is_value(bitmap)) {
- if (xa_to_value(rcu_dereference_raw(*slot)) == 0)
- radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
- } else if (bitmap_empty(btmp, IDA_BITMAP_BITS)) {
- kfree(bitmap);
- radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
+ if (!__test_and_clear_bit(bit, bitmap->bitmap))
+ goto err;
+ if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
+ kfree(bitmap);
+ xas_store(&ida->idxa, &xas, NULL);
+ }
}
+ xas_set_tag(&ida->idxa, &xas, XA_FREE_TAG);
+ xa_unlock_irqrestore(&ida->idxa, flags);
return;
err:
+ xa_unlock_irqrestore(&ida->idxa, flags);
WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
}
EXPORT_SYMBOL(ida_remove);
@@ -430,21 +438,21 @@ EXPORT_SYMBOL(ida_remove);
* @ida: ida handle
*
* Calling this function releases all resources associated with an IDA. When
- * this call returns, the IDA is empty and can be reused or freed. The caller
- * should not allow ida_remove() or ida_get_new_above() to be called at the
- * same time.
+ * this call returns, the IDA is empty and can be reused or freed.
*/
void ida_destroy(struct ida *ida)
{
- struct radix_tree_iter iter;
- void __rcu **slot;
+ XA_STATE(xas, 0);
+ unsigned long flags;
+ struct ida_bitmap *bitmap;

- radix_tree_for_each_slot(slot, &ida->ida_rt, &iter, 0) {
- struct ida_bitmap *bitmap = rcu_dereference_raw(*slot);
+ xa_lock_irqsave(&ida->idxa, flags);
+ xas_for_each(&ida->idxa, &xas, bitmap, ULONG_MAX) {
if (!xa_is_value(bitmap))
kfree(bitmap);
- radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
+ xas_store(&ida->idxa, &xas, NULL);
}
+ xa_unlock_irqrestore(&ida->idxa, flags);
}
EXPORT_SYMBOL(ida_destroy);

@@ -468,7 +476,6 @@ int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
{
int ret, id;
unsigned int max;
- unsigned long flags;

BUG_ON((int)start < 0);
BUG_ON((int)end < 0);
@@ -484,7 +491,6 @@ int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
if (!ida_pre_get(ida, gfp_mask))
return -ENOMEM;

- spin_lock_irqsave(&simple_ida_lock, flags);
ret = ida_get_new_above(ida, start, &id);
if (!ret) {
if (id > max) {
@@ -494,7 +500,6 @@ int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
ret = id;
}
}
- spin_unlock_irqrestore(&simple_ida_lock, flags);

if (unlikely(ret == -EAGAIN))
goto again;
@@ -515,11 +520,7 @@ EXPORT_SYMBOL(ida_simple_get);
*/
void ida_simple_remove(struct ida *ida, unsigned int id)
{
- unsigned long flags;
-
BUG_ON((int)id < 0);
- spin_lock_irqsave(&simple_ida_lock, flags);
ida_remove(ida, id);
- spin_unlock_irqrestore(&simple_ida_lock, flags);
}
EXPORT_SYMBOL(ida_simple_remove);
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 3fbc0751b181..f261fb2a92d2 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -247,13 +247,6 @@ static inline unsigned long node_maxindex(const struct radix_tree_node *node)
return shift_maxindex(node->shift);
}

-static unsigned long rnext_index(unsigned long index,
- const struct radix_tree_node *node,
- unsigned long offset)
-{
- return (index & ~node_maxindex(node)) + (offset << node->shift);
-}
-
#ifndef __KERNEL__
static void dump_node(struct radix_tree_node *node, unsigned long index)
{
@@ -338,10 +331,10 @@ static void dump_ida_node(void *entry, unsigned long index)

static void ida_dump(struct ida *ida)
{
- struct radix_tree_root *root = &ida->ida_rt;
- pr_debug("ida: %p node %p free %d\n", ida, root->xa_head,
- root->xa_flags >> ROOT_TAG_SHIFT);
- dump_ida_node(root->xa_head, 0);
+ struct xarray *xa = &ida->idxa;
+ pr_debug("ida: %p node %p free %d\n", ida, xa->xa_head,
+ xa->xa_flags >> ROOT_TAG_SHIFT);
+ dump_ida_node(xa->xa_head, 0);
}
#endif

@@ -2124,77 +2117,6 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
}
EXPORT_SYMBOL(ida_pre_get);

-void __rcu **idr_get_free(struct radix_tree_root *root,
- struct radix_tree_iter *iter, gfp_t gfp,
- unsigned long max)
-{
- struct radix_tree_node *node = NULL, *child;
- void __rcu **slot = (void __rcu **)&root->xa_head;
- unsigned long maxindex, start = iter->next_index;
- unsigned int shift, offset = 0;
-
- grow:
- shift = radix_tree_load_root(root, &child, &maxindex);
- if (!radix_tree_tagged(root, XA_FREE_TAG))
- start = max(start, maxindex + 1);
- if (start > max)
- return ERR_PTR(-ENOSPC);
-
- if (start > maxindex) {
- int error = radix_tree_extend(root, gfp, start, shift);
- if (error < 0)
- return ERR_PTR(error);
- shift = error;
- child = rcu_dereference_raw(root->xa_head);
- }
-
- while (shift) {
- shift -= RADIX_TREE_MAP_SHIFT;
- if (child == NULL) {
- /* Have to add a child node. */
- child = radix_tree_node_alloc(gfp, node, root, shift,
- offset, 0, 0);
- if (!child)
- return ERR_PTR(-ENOMEM);
- all_tag_set(child, XA_FREE_TAG);
- rcu_assign_pointer(*slot, node_to_entry(child));
- if (node)
- node->count++;
- } else if (!radix_tree_is_internal_node(child))
- break;
-
- node = entry_to_node(child);
- offset = radix_tree_descend(node, &child, start);
- if (!rtag_get(node, XA_FREE_TAG, offset)) {
- offset = radix_tree_find_next_bit(node, XA_FREE_TAG,
- offset + 1);
- start = rnext_index(start, node, offset);
- if (start > max)
- return ERR_PTR(-ENOSPC);
- while (offset == RADIX_TREE_MAP_SIZE) {
- offset = node->offset + 1;
- node = node->parent;
- if (!node)
- goto grow;
- shift = node->shift;
- }
- child = rcu_dereference_raw(node->slots[offset]);
- }
- slot = &node->slots[offset];
- }
-
- iter->index = start;
- if (node)
- iter->next_index = 1 + min(max, (start | node_maxindex(node)));
- else
- iter->next_index = 1;
- iter->node = node;
- __set_iter_shift(iter, shift);
- set_iter_tags(iter, node, offset, XA_FREE_TAG);
-
- return slot;
-}
-
static void
radix_tree_node_ctor(void *arg)
{
--
2.15.0