v4.19.13 snapshot.
diff --git a/lib/idr.c b/lib/idr.c
new file mode 100644
index 0000000..fab2fd5
--- /dev/null
+++ b/lib/idr.c
@@ -0,0 +1,579 @@
+#include <linux/bitmap.h>
+#include <linux/bug.h>
+#include <linux/export.h>
+#include <linux/idr.h>
+#include <linux/slab.h>
+#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.
+ * @ptr: Pointer to be associated with the new ID.
+ * @nextid: Pointer to an ID.
+ * @max: The maximum ID to allocate (inclusive).
+ * @gfp: Memory allocation flags.
+ *
+ * Allocates an unused ID in the range specified by @nextid and @max.
+ * Note that @max is inclusive whereas the @end parameter to idr_alloc()
+ * is exclusive. The new ID is assigned to @nextid before the pointer
+ * is inserted into the IDR, so if @nextid points into the object pointed
+ * to by @ptr, a concurrent lookup will not find an uninitialised ID.
+ *
+ * The caller should provide their own locking to ensure that two
+ * concurrent modifications to the IDR are not possible. Read-only
+ * accesses to the IDR may be done under the RCU read lock or may
+ * exclude simultaneous writers.
+ *
+ * Return: 0 if an ID was allocated, -ENOMEM if memory allocation failed,
+ * or -ENOSPC if no free IDs could be found. If an error occurred,
+ * @nextid is unchanged.
+ */
+int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
+ unsigned long max, gfp_t gfp)
+{
+ struct radix_tree_iter iter;
+ void __rcu **slot;
+ unsigned int base = idr->idr_base;
+ unsigned int id = *nextid;
+
+ if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
+ return -EINVAL;
+ if (WARN_ON_ONCE(!(idr->idr_rt.gfp_mask & ROOT_IS_IDR)))
+ idr->idr_rt.gfp_mask |= IDR_RT_MARKER;
+
+ id = (id < base) ? 0 : id - base;
+ radix_tree_iter_init(&iter, id);
+ slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base);
+ if (IS_ERR(slot))
+ return PTR_ERR(slot);
+
+ *nextid = iter.index + base;
+ /* there is a memory barrier inside radix_tree_iter_replace() */
+ radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
+ radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(idr_alloc_u32);
+
+/**
+ * idr_alloc() - Allocate an ID.
+ * @idr: IDR handle.
+ * @ptr: Pointer to be associated with the new ID.
+ * @start: The minimum ID (inclusive).
+ * @end: The maximum ID (exclusive).
+ * @gfp: Memory allocation flags.
+ *
+ * Allocates an unused ID in the range specified by @start and @end. If
+ * @end is <= 0, it is treated as one larger than %INT_MAX. This allows
+ * callers to use @start + N as @end as long as N is within integer range.
+ *
+ * The caller should provide their own locking to ensure that two
+ * concurrent modifications to the IDR are not possible. Read-only
+ * accesses to the IDR may be done under the RCU read lock or may
+ * exclude simultaneous writers.
+ *
+ * Return: The newly allocated ID, -ENOMEM if memory allocation failed,
+ * or -ENOSPC if no free IDs could be found.
+ */
+int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
+{
+ u32 id = start;
+ int ret;
+
+ if (WARN_ON_ONCE(start < 0))
+ return -EINVAL;
+
+ ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp);
+ if (ret)
+ return ret;
+
+ return id;
+}
+EXPORT_SYMBOL_GPL(idr_alloc);
+
+/**
+ * idr_alloc_cyclic() - Allocate an ID cyclically.
+ * @idr: IDR handle.
+ * @ptr: Pointer to be associated with the new ID.
+ * @start: The minimum ID (inclusive).
+ * @end: The maximum ID (exclusive).
+ * @gfp: Memory allocation flags.
+ *
+ * Allocates an unused ID in the range specified by @nextid and @end. If
+ * @end is <= 0, it is treated as one larger than %INT_MAX. This allows
+ * callers to use @start + N as @end as long as N is within integer range.
+ * The search for an unused ID will start at the last ID allocated and will
+ * wrap around to @start if no free IDs are found before reaching @end.
+ *
+ * The caller should provide their own locking to ensure that two
+ * concurrent modifications to the IDR are not possible. Read-only
+ * accesses to the IDR may be done under the RCU read lock or may
+ * exclude simultaneous writers.
+ *
+ * Return: The newly allocated ID, -ENOMEM if memory allocation failed,
+ * or -ENOSPC if no free IDs could be found.
+ */
+int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
+{
+ u32 id = idr->idr_next;
+ int err, max = end > 0 ? end - 1 : INT_MAX;
+
+ if ((int)id < start)
+ id = start;
+
+ err = idr_alloc_u32(idr, ptr, &id, max, gfp);
+ if ((err == -ENOSPC) && (id > start)) {
+ id = start;
+ err = idr_alloc_u32(idr, ptr, &id, max, gfp);
+ }
+ if (err)
+ return err;
+
+ idr->idr_next = id + 1;
+ return id;
+}
+EXPORT_SYMBOL(idr_alloc_cyclic);
+
+/**
+ * idr_remove() - Remove an ID from the IDR.
+ * @idr: IDR handle.
+ * @id: Pointer ID.
+ *
+ * Removes this ID from the IDR. If the ID was not previously in the IDR,
+ * this function returns %NULL.
+ *
+ * Since this function modifies the IDR, the caller should provide their
+ * own locking to ensure that concurrent modification of the same IDR is
+ * not possible.
+ *
+ * Return: The pointer formerly associated with this ID.
+ */
+void *idr_remove(struct idr *idr, unsigned long id)
+{
+ return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL);
+}
+EXPORT_SYMBOL_GPL(idr_remove);
+
+/**
+ * idr_find() - Return pointer for given ID.
+ * @idr: IDR handle.
+ * @id: Pointer ID.
+ *
+ * Looks up the pointer associated with this ID. A %NULL pointer may
+ * indicate that @id is not allocated or that the %NULL pointer was
+ * associated with this ID.
+ *
+ * This function can be called under rcu_read_lock(), given that the leaf
+ * pointers lifetimes are correctly managed.
+ *
+ * Return: The pointer associated with this ID.
+ */
+void *idr_find(const struct idr *idr, unsigned long id)
+{
+ return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base);
+}
+EXPORT_SYMBOL_GPL(idr_find);
+
+/**
+ * idr_for_each() - Iterate through all stored pointers.
+ * @idr: IDR handle.
+ * @fn: Function to be called for each pointer.
+ * @data: Data passed to callback function.
+ *
+ * The callback function will be called for each entry in @idr, passing
+ * the ID, the entry and @data.
+ *
+ * If @fn returns anything other than %0, the iteration stops and that
+ * value is returned from this function.
+ *
+ * idr_for_each() can be called concurrently with idr_alloc() and
+ * idr_remove() if protected by RCU. Newly added entries may not be
+ * seen and deleted entries may be seen, but adding and removing entries
+ * will not cause other entries to be skipped, nor spurious ones to be seen.
+ */
+int idr_for_each(const struct idr *idr,
+ int (*fn)(int id, void *p, void *data), void *data)
+{
+ struct radix_tree_iter iter;
+ void __rcu **slot;
+ int base = idr->idr_base;
+
+ radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
+ int ret;
+ unsigned long id = iter.index + base;
+
+ if (WARN_ON_ONCE(id > INT_MAX))
+ break;
+ ret = fn(id, rcu_dereference_raw(*slot), data);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(idr_for_each);
+
+/**
+ * idr_get_next() - Find next populated entry.
+ * @idr: IDR handle.
+ * @nextid: Pointer to an ID.
+ *
+ * Returns the next populated entry in the tree with an ID greater than
+ * or equal to the value pointed to by @nextid. On exit, @nextid is updated
+ * to the ID of the found value. To use in a loop, the value pointed to by
+ * nextid must be incremented by the user.
+ */
+void *idr_get_next(struct idr *idr, int *nextid)
+{
+ struct radix_tree_iter iter;
+ void __rcu **slot;
+ unsigned long base = idr->idr_base;
+ unsigned long id = *nextid;
+
+ id = (id < base) ? 0 : id - base;
+ slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
+ if (!slot)
+ return NULL;
+ id = iter.index + base;
+
+ if (WARN_ON_ONCE(id > INT_MAX))
+ return NULL;
+
+ *nextid = id;
+ return rcu_dereference_raw(*slot);
+}
+EXPORT_SYMBOL(idr_get_next);
+
+/**
+ * idr_get_next_ul() - Find next populated entry.
+ * @idr: IDR handle.
+ * @nextid: Pointer to an ID.
+ *
+ * Returns the next populated entry in the tree with an ID greater than
+ * or equal to the value pointed to by @nextid. On exit, @nextid is updated
+ * to the ID of the found value. To use in a loop, the value pointed to by
+ * nextid must be incremented by the user.
+ */
+void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)
+{
+ struct radix_tree_iter iter;
+ void __rcu **slot;
+ unsigned long base = idr->idr_base;
+ unsigned long id = *nextid;
+
+ id = (id < base) ? 0 : id - base;
+ slot = radix_tree_iter_find(&idr->idr_rt, &iter, id);
+ if (!slot)
+ return NULL;
+
+ *nextid = iter.index + base;
+ return rcu_dereference_raw(*slot);
+}
+EXPORT_SYMBOL(idr_get_next_ul);
+
+/**
+ * idr_replace() - replace pointer for given ID.
+ * @idr: IDR handle.
+ * @ptr: New pointer to associate with the ID.
+ * @id: ID to change.
+ *
+ * Replace the pointer registered with an ID and return the old value.
+ * This function can be called under the RCU read lock concurrently with
+ * idr_alloc() and idr_remove() (as long as the ID being removed is not
+ * the one being replaced!).
+ *
+ * Returns: the old value on success. %-ENOENT indicates that @id was not
+ * found. %-EINVAL indicates that @ptr was not valid.
+ */
+void *idr_replace(struct idr *idr, void *ptr, unsigned long id)
+{
+ struct radix_tree_node *node;
+ void __rcu **slot = NULL;
+ void *entry;
+
+ if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
+ return ERR_PTR(-EINVAL);
+ id -= idr->idr_base;
+
+ entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
+ if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
+ return ERR_PTR(-ENOENT);
+
+ __radix_tree_replace(&idr->idr_rt, node, slot, ptr, NULL);
+
+ return entry;
+}
+EXPORT_SYMBOL(idr_replace);
+
+/**
+ * DOC: IDA description
+ *
+ * The IDA is an ID allocator which does not provide the ability to
+ * associate an ID with a pointer. As such, it only needs to store one
+ * bit per ID, and so is more space efficient than an IDR. To use an IDA,
+ * define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
+ * then initialise it using ida_init()). To allocate a new ID, call
+ * ida_alloc(), ida_alloc_min(), ida_alloc_max() or ida_alloc_range().
+ * To free an ID, call ida_free().
+ *
+ * ida_destroy() can be used to dispose of an IDA without needing to
+ * free the individual IDs in it. You can use ida_is_empty() to find
+ * out whether the IDA has any IDs currently allocated.
+ *
+ * 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.
+ */
+
+/*
+ * 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.
+ *
+ * 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 use the 'exceptional
+ * entry' functionality of the radix tree to store BITS_PER_LONG - 2 bits
+ * directly in the entry. By being really tricksy, we could store
+ * BITS_PER_LONG - 1 bits, but there're diminishing returns after optimising
+ * for 0-3 allocated IDs.
+ *
+ * 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
+ * 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)
+{
+ 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, ebit;
+ int new;
+
+ index = start / IDA_BITMAP_BITS;
+ bit = start % IDA_BITMAP_BITS;
+ ebit = bit + RADIX_TREE_EXCEPTIONAL_SHIFT;
+
+ 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;
+ ebit = RADIX_TREE_EXCEPTIONAL_SHIFT;
+ }
+ new = iter.index * IDA_BITMAP_BITS;
+ bitmap = rcu_dereference_raw(*slot);
+ if (radix_tree_exception(bitmap)) {
+ unsigned long tmp = (unsigned long)bitmap;
+ ebit = find_next_zero_bit(&tmp, BITS_PER_LONG, ebit);
+ if (ebit < BITS_PER_LONG) {
+ tmp |= 1UL << ebit;
+ rcu_assign_pointer(*slot, (void *)tmp);
+ return new + ebit -
+ RADIX_TREE_EXCEPTIONAL_SHIFT;
+ }
+ bitmap = this_cpu_xchg(ida_bitmap, NULL);
+ if (!bitmap)
+ return -EAGAIN;
+ bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
+ rcu_assign_pointer(*slot, bitmap);
+ }
+
+ 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,
+ IDR_FREE);
+ } else {
+ new += bit;
+ if (new < 0)
+ return -ENOSPC;
+ if (ebit < BITS_PER_LONG) {
+ bitmap = (void *)((1UL << ebit) |
+ RADIX_TREE_EXCEPTIONAL_ENTRY);
+ radix_tree_iter_replace(root, &iter, slot,
+ bitmap);
+ return new;
+ }
+ bitmap = this_cpu_xchg(ida_bitmap, NULL);
+ if (!bitmap)
+ return -EAGAIN;
+ __set_bit(bit, bitmap->bitmap);
+ radix_tree_iter_replace(root, &iter, slot, bitmap);
+ }
+
+ return new;
+ }
+}
+
+static void ida_remove(struct ida *ida, int id)
+{
+ unsigned long index = id / IDA_BITMAP_BITS;
+ unsigned offset = id % IDA_BITMAP_BITS;
+ 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)
+ goto err;
+
+ bitmap = rcu_dereference_raw(*slot);
+ if (radix_tree_exception(bitmap)) {
+ btmp = (unsigned long *)slot;
+ offset += RADIX_TREE_EXCEPTIONAL_SHIFT;
+ if (offset >= BITS_PER_LONG)
+ goto err;
+ } 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 (radix_tree_exception(bitmap)) {
+ if (rcu_dereference_raw(*slot) ==
+ (void *)RADIX_TREE_EXCEPTIONAL_ENTRY)
+ 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);
+ }
+ return;
+ err:
+ WARN(1, "ida_free called for id=%d which is not allocated.\n", id);
+}
+
+/**
+ * ida_destroy() - Free all IDs.
+ * @ida: IDA handle.
+ *
+ * Calling this function frees all IDs and releases all resources used
+ * by an IDA. When this call returns, the IDA is empty and can be reused
+ * or freed. If the IDA is already empty, there is no need to call this
+ * function.
+ *
+ * Context: Any context.
+ */
+void ida_destroy(struct ida *ida)
+{
+ 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);
+ if (!radix_tree_exception(bitmap))
+ kfree(bitmap);
+ radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
+ }
+ xa_unlock_irqrestore(&ida->ida_rt, 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;
+
+ 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);
+
+ if (unlikely(id == -EAGAIN)) {
+ if (!ida_pre_get(ida, gfp))
+ return -ENOMEM;
+ goto again;
+ }
+
+ 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)
+{
+ 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);
+}
+EXPORT_SYMBOL(ida_free);