From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
---
include/linux/idr.h | 8 +-
include/linux/radix-tree.h | 4 -
lib/idr.c | 320 ++++++++++++++++++++++++++-------------------
lib/radix-tree.c | 119 -----------------
4 files changed, 187 insertions(+), 264 deletions(-)
diff --git a/include/linux/idr.h b/include/linux/idr.h
index 9064ae5f0abc..ad4199247301 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -232,11 +232,11 @@ struct ida_bitmap {
DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);
struct ida {
- struct radix_tree_root ida_rt;
+ struct xarray ida_xa;
};
#define IDA_INIT(name) { \
- .ida_rt = RADIX_TREE_INIT(name, IDR_INIT_FLAGS | GFP_NOWAIT), \
+ .ida_xa = XARRAY_INIT_FLAGS(name.ida_xa, IDR_INIT_FLAGS) \
}
#define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
@@ -251,7 +251,7 @@ 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_flags(&ida->ida_xa, IDR_INIT_FLAGS);
}
/**
@@ -268,6 +268,6 @@ 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->ida_xa);
}
#endif /* _LINUX_IDR_H */
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index f64beb9ba175..4c5c36414a80 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -302,10 +302,6 @@ 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 379eaa8cb75b..7e9a8850b613 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -13,7 +13,6 @@
#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);
@@ -337,26 +336,23 @@ EXPORT_SYMBOL_GPL(idr_replace);
/*
* Developer's notes:
*
- * The IDA uses the functionality provided by the IDR & radix tree to store
- * bitmaps in each entry. The XA_FREE_TAG tag means there is at least one bit
- * free, unlike the IDR where it means at least one entry is free.
- *
- * I considered telling the radix tree that each slot is an order-10 node
- * and storing the bit numbers in the radix tree, but the radix tree can't
- * allow a single multiorder entry at index 0, which would significantly
- * increase memory consumption for the IDA. So instead we divide the index
- * by the number of bits in the leaf bitmap before doing a radix tree lookup.
- *
- * As an optimisation, if there are only a few low bits set in any given
- * leaf, instead of allocating a 128-byte bitmap, we store the bits
+ * The IDA uses the functionality provided by the IDR & XArray to store
+ * bitmaps in each entry. The XA_FREE_TAG tag is used to mean that there
+ * is at least one bit free, unlike the IDR where it means at least one
+ * array entry is free.
+ *
+ * The XArray supports multi-index entries, so I considered teaching the
+ * XArray that each slot is an order-10 node and indexing the XArray by the
+ * ID. The XArray has the significant optimisation of storing the first
+ * entry in the struct xarray and avoiding allocating an xa_node.
+ * Unfortunately, it can't do that for multi-order entries.
+ * So instead the XArray index is the ID divided by the number of bits in
+ * the bitmap
+ *
+ * As a further optimisation, if there are only a few low bits set in any
+ * given leaf, instead of allocating a 128-byte bitmap, we store the bits
* directly in the entry.
*
- * We allow the radix tree 'exceptional' count to get out of date. Nothing
- * in the IDA nor the radix tree code checks it. If it becomes important
- * to maintain an accurate exceptional count, switch the rcu_assign_pointer()
- * calls to radix_tree_iter_replace() which will correct the exceptional
- * count.
- *
* The IDA always requires a lock to alloc/free. If we add a 'test_bit'
* equivalent, it will still need locking. Going to RCU lookup would require
* using RCU to free bitmaps, and that's not trivial without embedding an
@@ -366,104 +362,114 @@ 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, &ida->ida_xa, 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;
+
+ xas_lock_irqsave(&xas, flags);
+retry:
+ bitmap = xas_find_tag(&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(&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(&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(&xas, XA_FREE_TAG);
+ } else if (bit < BITS_PER_XA_VALUE) {
+ new += bit;
+ bitmap = xa_mk_value(1UL << bit);
+ xas_store(&xas, bitmap);
+ } else {
+ bitmap = alloc_ida_bitmap();
+ if (!bitmap)
+ goto nomem;
+ new += bit;
+ __set_bit(bit, bitmap->bitmap);
+ xas_store(&xas, bitmap);
+ if (xas_error(&xas))
+ free_ida_bitmap(bitmap);
}
+
+ if (idr_nomem(&xas, GFP_NOWAIT))
+ goto retry;
+unlock:
+ xas_unlock_irqrestore(&xas, flags);
+ if (xas_error(&xas) == -ENOMEM)
+ return -EAGAIN;
+ *id = new;
+ return 0;
+nospc:
+ xas_unlock_irqrestore(&xas, flags);
+ return -ENOSPC;
+nomem:
+ xas_unlock_irqrestore(&xas, flags);
+ return -EAGAIN;
}
EXPORT_SYMBOL(ida_get_new_above);
@@ -471,45 +477,44 @@ 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, &ida->ida_xa, 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)
+ xas_lock_irqsave(&xas, flags);
+ bitmap = xas_load(&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(&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(&xas, NULL);
+ }
}
+ xas_set_tag(&xas, XA_FREE_TAG);
+ xas_unlock_irqrestore(&xas, flags);
return;
err:
+ xas_unlock_irqrestore(&xas, flags);
WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
}
EXPORT_SYMBOL(ida_remove);
@@ -519,21 +524,21 @@ 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, &ida->ida_xa, 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);
+ xas_lock_irqsave(&xas, flags);
+ xas_for_each(&xas, bitmap, ULONG_MAX) {
if (!xa_is_value(bitmap))
kfree(bitmap);
- radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
+ xas_store(&xas, NULL);
}
+ xas_unlock_irqrestore(&xas, flags);
}
EXPORT_SYMBOL(ida_destroy);
@@ -557,7 +562,6 @@ 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);
@@ -573,7 +577,6 @@ 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) {
@@ -583,7 +586,6 @@ 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;
@@ -604,11 +606,55 @@ 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);
+
+#ifdef XA_DEBUG
+static void dump_ida_node(void *entry, unsigned long index)
+{
+ unsigned long i;
+
+ if (!entry)
+ return;
+
+ if (xa_is_node(entry)) {
+ struct xa_node *node = xa_to_node(entry);
+ unsigned long first = index * IDA_BITMAP_BITS;
+ unsigned long last = first | ((((unsigned long)XA_CHUNK_SIZE *
+ IDA_BITMAP_BITS) << node->shift) - 1);
+
+ pr_debug("ida node: %p offset %d indices %lu-%lu parent %p free %lx shift %d count %d\n",
+ node, node->offset, first, last, node->parent,
+ node->tags[0][0], node->shift, node->count);
+ for (i = 0; i < XA_CHUNK_SIZE; i++)
+ dump_ida_node(node->slots[i],
+ index | (i << node->shift));
+ } else if (xa_is_value(entry)) {
+ pr_debug("ida excp: %p offset %d indices %lu-%lu data %lx\n",
+ entry, (int)(index & XA_CHUNK_MASK),
+ index * IDA_BITMAP_BITS,
+ index * IDA_BITMAP_BITS + BITS_PER_XA_VALUE,
+ xa_to_value(entry));
+ } else {
+ struct ida_bitmap *bitmap = entry;
+
+ pr_debug("ida btmp: %p offset %d indices %lu-%lu data", bitmap,
+ (int)(index & XA_CHUNK_MASK),
+ index * IDA_BITMAP_BITS,
+ (index + 1) * IDA_BITMAP_BITS - 1);
+ for (i = 0; i < IDA_BITMAP_LONGS; i++)
+ pr_cont(" %lx", bitmap->bitmap[i]);
+ pr_cont("\n");
+ }
+}
+
+void ida_dump(struct ida *ida)
+{
+ struct xarray *xa = &ida->ida_xa;
+ pr_debug("ida: %p node %p free %d\n", ida, xa->xa_head,
+ xa_tagged(xa, XA_FREE_TAG));
+ dump_ida_node(xa->xa_head, 0);
+}
+#endif
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 75e02cb78ada..6f653d02a079 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -254,54 +254,6 @@ static unsigned long next_index(unsigned long index,
return (index & ~node_maxindex(node)) + (offset << node->shift);
}
-#ifndef __KERNEL__
-static void dump_ida_node(void *entry, unsigned long index)
-{
- unsigned long i;
-
- if (!entry)
- return;
-
- if (radix_tree_is_internal_node(entry)) {
- struct radix_tree_node *node = entry_to_node(entry);
-
- pr_debug("ida node: %p offset %d indices %lu-%lu parent %p free %lx shift %d count %d\n",
- node, node->offset, index * IDA_BITMAP_BITS,
- ((index | node_maxindex(node)) + 1) *
- IDA_BITMAP_BITS - 1,
- node->parent, node->tags[0][0], node->shift,
- node->count);
- for (i = 0; i < RADIX_TREE_MAP_SIZE; i++)
- dump_ida_node(node->slots[i],
- index | (i << node->shift));
- } 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_XA_VALUE,
- xa_to_value(entry));
- } else {
- struct ida_bitmap *bitmap = entry;
-
- pr_debug("ida btmp: %p offset %d indices %lu-%lu data", bitmap,
- (int)(index & RADIX_TREE_MAP_MASK),
- index * IDA_BITMAP_BITS,
- (index + 1) * IDA_BITMAP_BITS - 1);
- for (i = 0; i < IDA_BITMAP_LONGS; i++)
- pr_cont(" %lx", bitmap->bitmap[i]);
- pr_cont("\n");
- }
-}
-
-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);
-}
-#endif
-
/*
* This assumes that the caller has performed appropriate preallocation, and
* that the caller has pinned this thread of control to the current CPU.
@@ -2083,77 +2035,6 @@ 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 (!tag_get(node, XA_FREE_TAG, offset)) {
- offset = radix_tree_find_next_bit(node, XA_FREE_TAG,
- offset + 1);
- start = next_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)
{
--
2.15.1
--
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