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-rw-r--r--lib/idr.c379
-rw-r--r--lib/radix-tree.c71
2 files changed, 203 insertions, 247 deletions
diff --git a/lib/idr.c b/lib/idr.c
index 9a366b5be2c2..3c20ad9b0463 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -6,8 +6,6 @@
#include <linux/spinlock.h>
#include <linux/xarray.h>
-DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
-
/**
* idr_alloc_u32() - Allocate an ID.
* @idr: IDR handle.
@@ -320,6 +318,9 @@ EXPORT_SYMBOL(idr_replace);
* free the individual IDs in it. You can use ida_is_empty() to find
* out whether the IDA has any IDs currently allocated.
*
+ * The IDA handles its own locking. It is safe to call any of the IDA
+ * functions without synchronisation in your code.
+ *
* IDs are currently limited to the range [0-INT_MAX]. If this is an awkward
* limitation, it should be quite straightforward to raise the maximum.
*/
@@ -327,151 +328,197 @@ EXPORT_SYMBOL(idr_replace);
/*
* Developer's notes:
*
- * The IDA uses the functionality provided by the IDR & radix tree to store
- * bitmaps in each entry. The IDR_FREE tag means there is at least one bit
- * free, unlike the IDR where it means at least one entry is free.
+ * The IDA uses the functionality provided by the XArray to store bitmaps in
+ * each entry. The XA_FREE_MARK is only cleared when all bits in the bitmap
+ * have been set.
*
- * 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.
+ * I considered telling the XArray that each slot is an order-10 node
+ * and indexing by bit number, but the XArray can't allow a single multi-index
+ * entry in the head, 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
- * 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- * We allow the radix tree 'exceptional' count to get out of date.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'
+ * as a value entry. Value entries never have the XA_FREE_MARK cleared
+ * because we can always convert them into a bitmap entry.
+ *
+ * It would be possible to optimise further; once we've run out of a
+ * single 128-byte bitmap, we currently switch to a 576-byte node, put
+ * the 128-byte bitmap in the first entry and then start allocating extra
+ * 128-byte entries. We could instead use the 512 bytes of the node's
+ * data as a bitmap before moving to that scheme. I do not believe this
+ * is a worthwhile optimisation; Rasmus Villemoes surveyed the current
+ * users of the IDA and almost none of them use more than 1024 entries.
+ * Those that do use more than the 8192 IDs that the 512 bytes would
+ * provide.
+ *
+ * The IDA always uses 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
* RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte
* bitmap, which is excessive.
*/
-#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS - 1)
-
-static int ida_get_new_above(struct ida *ida, int start)
+/**
+ * ida_alloc_range() - Allocate an unused ID.
+ * @ida: IDA handle.
+ * @min: Lowest ID to allocate.
+ * @max: Highest ID to allocate.
+ * @gfp: Memory allocation flags.
+ *
+ * Allocate an ID between @min and @max, inclusive. The allocated ID will
+ * not exceed %INT_MAX, even if @max is larger.
+ *
+ * Context: Any context.
+ * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,
+ * or %-ENOSPC if there are no free IDs.
+ */
+int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,
+ gfp_t gfp)
{
- struct radix_tree_root *root = &ida->ida_rt;
- void __rcu **slot;
- struct radix_tree_iter iter;
- 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);
+ XA_STATE(xas, &ida->xa, min / IDA_BITMAP_BITS);
+ unsigned bit = min % IDA_BITMAP_BITS;
+ unsigned long flags;
+ struct ida_bitmap *bitmap, *alloc = NULL;
+
+ if ((int)min < 0)
+ return -ENOSPC;
+
+ if ((int)max < 0)
+ max = INT_MAX;
+
+retry:
+ xas_lock_irqsave(&xas, flags);
+next:
+ bitmap = xas_find_marked(&xas, max / IDA_BITMAP_BITS, XA_FREE_MARK);
+ if (xas.xa_index > min / IDA_BITMAP_BITS)
+ bit = 0;
+ if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
+ goto nospc;
+
+ if (xa_is_value(bitmap)) {
+ unsigned long tmp = xa_to_value(bitmap);
+
+ if (bit < BITS_PER_XA_VALUE) {
+ bit = find_next_zero_bit(&tmp, BITS_PER_XA_VALUE, bit);
+ if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
+ goto nospc;
+ if (bit < BITS_PER_XA_VALUE) {
+ tmp |= 1UL << bit;
+ xas_store(&xas, xa_mk_value(tmp));
+ goto out;
}
}
- 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));
- return new + vbit;
- }
- bitmap = this_cpu_xchg(ida_bitmap, NULL);
- if (!bitmap)
- return -EAGAIN;
- bitmap->bitmap[0] = tmp;
- rcu_assign_pointer(*slot, bitmap);
+ bitmap = alloc;
+ if (!bitmap)
+ bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT);
+ if (!bitmap)
+ goto alloc;
+ bitmap->bitmap[0] = tmp;
+ xas_store(&xas, bitmap);
+ if (xas_error(&xas)) {
+ bitmap->bitmap[0] = 0;
+ goto out;
}
+ }
- 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;
+ if (bitmap) {
+ bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit);
+ if (xas.xa_index * IDA_BITMAP_BITS + bit > max)
+ goto nospc;
+ if (bit == IDA_BITMAP_BITS)
+ goto next;
- __set_bit(bit, bitmap->bitmap);
- if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
- radix_tree_iter_tag_clear(root, &iter,
- IDR_FREE);
+ __set_bit(bit, bitmap->bitmap);
+ if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
+ xas_clear_mark(&xas, XA_FREE_MARK);
+ } else {
+ if (bit < BITS_PER_XA_VALUE) {
+ bitmap = xa_mk_value(1UL << bit);
} 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;
- __set_bit(bit, bitmap->bitmap);
- }
- radix_tree_iter_replace(root, &iter, slot, bitmap);
+ bitmap = alloc;
+ if (!bitmap)
+ bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT);
+ if (!bitmap)
+ goto alloc;
+ __set_bit(bit, bitmap->bitmap);
}
-
- return new;
+ xas_store(&xas, bitmap);
+ }
+out:
+ xas_unlock_irqrestore(&xas, flags);
+ if (xas_nomem(&xas, gfp)) {
+ xas.xa_index = min / IDA_BITMAP_BITS;
+ bit = min % IDA_BITMAP_BITS;
+ goto retry;
}
+ if (bitmap != alloc)
+ kfree(alloc);
+ if (xas_error(&xas))
+ return xas_error(&xas);
+ return xas.xa_index * IDA_BITMAP_BITS + bit;
+alloc:
+ xas_unlock_irqrestore(&xas, flags);
+ alloc = kzalloc(sizeof(*bitmap), gfp);
+ if (!alloc)
+ return -ENOMEM;
+ xas_set(&xas, min / IDA_BITMAP_BITS);
+ bit = min % IDA_BITMAP_BITS;
+ goto retry;
+nospc:
+ xas_unlock_irqrestore(&xas, flags);
+ return -ENOSPC;
}
+EXPORT_SYMBOL(ida_alloc_range);
-static void ida_remove(struct ida *ida, int id)
+/**
+ * ida_free() - Release an allocated ID.
+ * @ida: IDA handle.
+ * @id: Previously allocated ID.
+ *
+ * Context: Any context.
+ */
+void ida_free(struct ida *ida, unsigned int id)
{
- unsigned long index = id / IDA_BITMAP_BITS;
- unsigned offset = id % IDA_BITMAP_BITS;
+ XA_STATE(xas, &ida->xa, id / IDA_BITMAP_BITS);
+ unsigned bit = id % IDA_BITMAP_BITS;
struct ida_bitmap *bitmap;
- unsigned long *btmp;
- struct radix_tree_iter iter;
- void __rcu **slot;
+ unsigned long flags;
- slot = radix_tree_iter_lookup(&ida->ida_rt, &iter, index);
- if (!slot)
- goto err;
+ BUG_ON((int)id < 0);
+
+ xas_lock_irqsave(&xas, flags);
+ bitmap = xas_load(&xas);
- bitmap = rcu_dereference_raw(*slot);
if (xa_is_value(bitmap)) {
- btmp = (unsigned long *)slot;
- offset += 1; /* Intimate knowledge of the value 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)
+ goto delete;
+ xas_store(&xas, xa_mk_value(v));
} else {
- btmp = bitmap->bitmap;
- }
- if (!test_bit(offset, btmp))
- goto err;
-
- __clear_bit(offset, btmp);
- radix_tree_iter_tag_set(&ida->ida_rt, &iter, IDR_FREE);
- 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_bit(bit, bitmap->bitmap))
+ goto err;
+ __clear_bit(bit, bitmap->bitmap);
+ xas_set_mark(&xas, XA_FREE_MARK);
+ if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
+ kfree(bitmap);
+delete:
+ xas_store(&xas, NULL);
+ }
}
+ xas_unlock_irqrestore(&xas, flags);
return;
err:
+ xas_unlock_irqrestore(&xas, flags);
WARN(1, "ida_free called for id=%d which is not allocated.\n", id);
}
+EXPORT_SYMBOL(ida_free);
/**
* ida_destroy() - Free all IDs.
@@ -486,80 +533,60 @@ static void ida_remove(struct ida *ida, int id)
*/
void ida_destroy(struct ida *ida)
{
+ XA_STATE(xas, &ida->xa, 0);
+ struct ida_bitmap *bitmap;
unsigned long flags;
- struct radix_tree_iter iter;
- void __rcu **slot;
- xa_lock_irqsave(&ida->ida_rt, flags);
- 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);
}
- xa_unlock_irqrestore(&ida->ida_rt, flags);
+ xas_unlock_irqrestore(&xas, flags);
}
EXPORT_SYMBOL(ida_destroy);
-/**
- * ida_alloc_range() - Allocate an unused ID.
- * @ida: IDA handle.
- * @min: Lowest ID to allocate.
- * @max: Highest ID to allocate.
- * @gfp: Memory allocation flags.
- *
- * Allocate an ID between @min and @max, inclusive. The allocated ID will
- * not exceed %INT_MAX, even if @max is larger.
- *
- * Context: Any context.
- * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,
- * or %-ENOSPC if there are no free IDs.
- */
-int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,
- gfp_t gfp)
-{
- int id = 0;
- unsigned long flags;
-
- if ((int)min < 0)
- return -ENOSPC;
+#ifndef __KERNEL__
+extern void xa_dump_index(unsigned long index, unsigned int shift);
+#define IDA_CHUNK_SHIFT ilog2(IDA_BITMAP_BITS)
- if ((int)max < 0)
- max = INT_MAX;
-
-again:
- xa_lock_irqsave(&ida->ida_rt, flags);
- id = ida_get_new_above(ida, min);
- if (id > (int)max) {
- ida_remove(ida, id);
- id = -ENOSPC;
- }
- xa_unlock_irqrestore(&ida->ida_rt, flags);
+static void ida_dump_entry(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 int shift = node->shift + IDA_CHUNK_SHIFT +
+ XA_CHUNK_SHIFT;
+
+ xa_dump_index(index * IDA_BITMAP_BITS, shift);
+ xa_dump_node(node);
+ for (i = 0; i < XA_CHUNK_SIZE; i++)
+ ida_dump_entry(node->slots[i],
+ index | (i << node->shift));
+ } else if (xa_is_value(entry)) {
+ xa_dump_index(index * IDA_BITMAP_BITS, ilog2(BITS_PER_LONG));
+ pr_cont("value: data %lx [%px]\n", xa_to_value(entry), entry);
+ } else {
+ struct ida_bitmap *bitmap = entry;
- if (unlikely(id == -EAGAIN)) {
- if (!ida_pre_get(ida, gfp))
- return -ENOMEM;
- goto again;
+ xa_dump_index(index * IDA_BITMAP_BITS, IDA_CHUNK_SHIFT);
+ pr_cont("bitmap: %p data", bitmap);
+ for (i = 0; i < IDA_BITMAP_LONGS; i++)
+ pr_cont(" %lx", bitmap->bitmap[i]);
+ pr_cont("\n");
}
-
- return id;
}
-EXPORT_SYMBOL(ida_alloc_range);
-/**
- * ida_free() - Release an allocated ID.
- * @ida: IDA handle.
- * @id: Previously allocated ID.
- *
- * Context: Any context.
- */
-void ida_free(struct ida *ida, unsigned int id)
+static void ida_dump(struct ida *ida)
{
- unsigned long flags;
-
- BUG_ON((int)id < 0);
- xa_lock_irqsave(&ida->ida_rt, flags);
- ida_remove(ida, id);
- xa_unlock_irqrestore(&ida->ida_rt, flags);
+ struct xarray *xa = &ida->xa;
+ pr_debug("ida: %p node %p free %d\n", ida, xa->xa_head,
+ xa->xa_flags >> ROOT_TAG_SHIFT);
+ ida_dump_entry(xa->xa_head, 0);
}
-EXPORT_SYMBOL(ida_free);
+#endif
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 3479d93c32b9..68702061464f 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -255,54 +255,6 @@ 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.
@@ -2039,27 +1991,6 @@ void idr_preload(gfp_t gfp_mask)
}
EXPORT_SYMBOL(idr_preload);
-int ida_pre_get(struct ida *ida, gfp_t gfp)
-{
- /*
- * The IDA API has no preload_end() equivalent. Instead,
- * ida_get_new() can return -EAGAIN, prompting the caller
- * to return to the ida_pre_get() step.
- */
- if (!__radix_tree_preload(gfp, IDA_PRELOAD_SIZE))
- preempt_enable();
-
- if (!this_cpu_read(ida_bitmap)) {
- struct ida_bitmap *bitmap = kzalloc(sizeof(*bitmap), gfp);
- if (!bitmap)
- return 0;
- if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
- kfree(bitmap);
- }
-
- return 1;
-}
-
void __rcu **idr_get_free(struct radix_tree_root *root,
struct radix_tree_iter *iter, gfp_t gfp,
unsigned long max)
@@ -2201,8 +2132,6 @@ static int radix_tree_cpu_dead(unsigned int cpu)
kmem_cache_free(radix_tree_node_cachep, node);
rtp->nr--;
}
- kfree(per_cpu(ida_bitmap, cpu));
- per_cpu(ida_bitmap, cpu) = NULL;
return 0;
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-29 16:58:29 +0000