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https://github.com/edk2-porting/linux-next.git
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7e73eb0b2d
Where we use the radix tree iteration macros, we need to annotate 'slot' with __rcu. Make sure we don't forget any new places in the future with the same CFLAGS check used for radix-tree.c. Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
485 lines
14 KiB
C
485 lines
14 KiB
C
#include <linux/bitmap.h>
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#include <linux/export.h>
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#include <linux/idr.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
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static DEFINE_SPINLOCK(simple_ida_lock);
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/**
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* idr_alloc - allocate an id
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* @idr: idr handle
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* @ptr: pointer to be associated with the new id
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* @start: the minimum id (inclusive)
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* @end: the maximum id (exclusive)
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* @gfp: memory allocation flags
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*
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* Allocates an unused ID in the range [start, end). Returns -ENOSPC
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* if there are no unused IDs in that range.
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*
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* Note that @end is treated as max when <= 0. This is to always allow
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* using @start + N as @end as long as N is inside integer range.
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*
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* Simultaneous modifications to the @idr are not allowed and should be
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* prevented by the user, usually with a lock. idr_alloc() may be called
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* concurrently with read-only accesses to the @idr, such as idr_find() and
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* idr_for_each_entry().
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*/
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int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
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{
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void __rcu **slot;
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struct radix_tree_iter iter;
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if (WARN_ON_ONCE(start < 0))
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return -EINVAL;
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if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
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return -EINVAL;
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radix_tree_iter_init(&iter, start);
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slot = idr_get_free(&idr->idr_rt, &iter, gfp, end);
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if (IS_ERR(slot))
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return PTR_ERR(slot);
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radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
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radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
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return iter.index;
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}
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EXPORT_SYMBOL_GPL(idr_alloc);
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/**
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* idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
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* @idr: idr handle
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* @ptr: pointer to be associated with the new id
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* @start: the minimum id (inclusive)
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* @end: the maximum id (exclusive)
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* @gfp: memory allocation flags
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*
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* Allocates an ID larger than the last ID allocated if one is available.
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* If not, it will attempt to allocate the smallest ID that is larger or
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* equal to @start.
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*/
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int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
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{
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int id, curr = idr->idr_next;
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if (curr < start)
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curr = start;
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id = idr_alloc(idr, ptr, curr, end, gfp);
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if ((id == -ENOSPC) && (curr > start))
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id = idr_alloc(idr, ptr, start, curr, gfp);
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if (id >= 0)
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idr->idr_next = id + 1U;
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return id;
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}
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EXPORT_SYMBOL(idr_alloc_cyclic);
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/**
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* idr_for_each - iterate through all stored pointers
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* @idr: idr handle
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* @fn: function to be called for each pointer
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* @data: data passed to callback function
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*
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* The callback function will be called for each entry in @idr, passing
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* the id, the pointer and the data pointer passed to this function.
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*
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* If @fn returns anything other than %0, the iteration stops and that
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* value is returned from this function.
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*
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* idr_for_each() can be called concurrently with idr_alloc() and
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* idr_remove() if protected by RCU. Newly added entries may not be
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* seen and deleted entries may be seen, but adding and removing entries
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* will not cause other entries to be skipped, nor spurious ones to be seen.
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*/
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int idr_for_each(const struct idr *idr,
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int (*fn)(int id, void *p, void *data), void *data)
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{
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struct radix_tree_iter iter;
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void __rcu **slot;
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radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
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int ret = fn(iter.index, rcu_dereference_raw(*slot), data);
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if (ret)
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return ret;
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}
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return 0;
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}
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EXPORT_SYMBOL(idr_for_each);
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/**
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* idr_get_next - Find next populated entry
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* @idr: idr handle
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* @nextid: Pointer to lowest possible ID to return
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*
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* Returns the next populated entry in the tree with an ID greater than
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* or equal to the value pointed to by @nextid. On exit, @nextid is updated
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* to the ID of the found value. To use in a loop, the value pointed to by
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* nextid must be incremented by the user.
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*/
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void *idr_get_next(struct idr *idr, int *nextid)
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{
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struct radix_tree_iter iter;
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void __rcu **slot;
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slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid);
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if (!slot)
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return NULL;
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*nextid = iter.index;
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return rcu_dereference_raw(*slot);
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}
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EXPORT_SYMBOL(idr_get_next);
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/**
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* idr_replace - replace pointer for given id
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* @idr: idr handle
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* @ptr: New pointer to associate with the ID
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* @id: Lookup key
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*
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* Replace the pointer registered with an ID and return the old value.
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* This function can be called under the RCU read lock concurrently with
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* idr_alloc() and idr_remove() (as long as the ID being removed is not
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* the one being replaced!).
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*
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* Returns: 0 on success. %-ENOENT indicates that @id was not found.
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* %-EINVAL indicates that @id or @ptr were not valid.
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*/
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void *idr_replace(struct idr *idr, void *ptr, int id)
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{
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struct radix_tree_node *node;
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void __rcu **slot = NULL;
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void *entry;
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if (WARN_ON_ONCE(id < 0))
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return ERR_PTR(-EINVAL);
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if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
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return ERR_PTR(-EINVAL);
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entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
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if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
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return ERR_PTR(-ENOENT);
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__radix_tree_replace(&idr->idr_rt, node, slot, ptr, NULL, NULL);
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return entry;
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}
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EXPORT_SYMBOL(idr_replace);
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/**
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* DOC: IDA description
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*
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* The IDA is an ID allocator which does not provide the ability to
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* associate an ID with a pointer. As such, it only needs to store one
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* bit per ID, and so is more space efficient than an IDR. To use an IDA,
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* define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
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* then initialise it using ida_init()). To allocate a new ID, call
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* ida_simple_get(). To free an ID, call ida_simple_remove().
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*
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* If you have more complex locking requirements, use a loop around
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* ida_pre_get() and ida_get_new() to allocate a new ID. Then use
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* ida_remove() to free an ID. You must make sure that ida_get_new() and
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* ida_remove() cannot be called at the same time as each other for the
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* same IDA.
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*
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* You can also use ida_get_new_above() if you need an ID to be allocated
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* above a particular number. ida_destroy() can be used to dispose of an
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* IDA without needing to free the individual IDs in it. You can use
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* ida_is_empty() to find out whether the IDA has any IDs currently allocated.
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*
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* IDs are currently limited to the range [0-INT_MAX]. If this is an awkward
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* limitation, it should be quite straightforward to raise the maximum.
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*/
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/*
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* Developer's notes:
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*
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* The IDA uses the functionality provided by the IDR & radix tree to store
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* bitmaps in each entry. The IDR_FREE tag means there is at least one bit
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* free, unlike the IDR where it means at least one entry is free.
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*
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* I considered telling the radix tree that each slot is an order-10 node
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* and storing the bit numbers in the radix tree, but the radix tree can't
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* allow a single multiorder entry at index 0, which would significantly
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* increase memory consumption for the IDA. So instead we divide the index
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* by the number of bits in the leaf bitmap before doing a radix tree lookup.
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*
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* As an optimisation, if there are only a few low bits set in any given
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* leaf, instead of allocating a 128-byte bitmap, we use the 'exceptional
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* entry' functionality of the radix tree to store BITS_PER_LONG - 2 bits
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* directly in the entry. By being really tricksy, we could store
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* BITS_PER_LONG - 1 bits, but there're diminishing returns after optimising
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* for 0-3 allocated IDs.
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*
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* We allow the radix tree 'exceptional' count to get out of date. Nothing
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* in the IDA nor the radix tree code checks it. If it becomes important
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* to maintain an accurate exceptional count, switch the rcu_assign_pointer()
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* calls to radix_tree_iter_replace() which will correct the exceptional
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* count.
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*
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* The IDA always requires a lock to alloc/free. If we add a 'test_bit'
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* equivalent, it will still need locking. Going to RCU lookup would require
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* using RCU to free bitmaps, and that's not trivial without embedding an
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* RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte
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* bitmap, which is excessive.
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*/
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#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS)
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/**
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* ida_get_new_above - allocate new ID above or equal to a start id
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* @ida: ida handle
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* @start: id to start search at
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* @id: pointer to the allocated handle
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*
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* Allocate new ID above or equal to @start. It should be called
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* with any required locks to ensure that concurrent calls to
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* ida_get_new_above() / ida_get_new() / ida_remove() are not allowed.
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* Consider using ida_simple_get() if you do not have complex locking
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* requirements.
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*
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* If memory is required, it will return %-EAGAIN, you should unlock
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* and go back to the ida_pre_get() call. If the ida is full, it will
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* return %-ENOSPC. On success, it will return 0.
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*
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* @id returns a value in the range @start ... %0x7fffffff.
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*/
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int ida_get_new_above(struct ida *ida, int start, int *id)
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{
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struct radix_tree_root *root = &ida->ida_rt;
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void __rcu **slot;
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struct radix_tree_iter iter;
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struct ida_bitmap *bitmap;
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unsigned long index;
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unsigned bit, ebit;
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int new;
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index = start / IDA_BITMAP_BITS;
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bit = start % IDA_BITMAP_BITS;
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ebit = bit + RADIX_TREE_EXCEPTIONAL_SHIFT;
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slot = radix_tree_iter_init(&iter, index);
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for (;;) {
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if (slot)
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slot = radix_tree_next_slot(slot, &iter,
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RADIX_TREE_ITER_TAGGED);
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if (!slot) {
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slot = idr_get_free(root, &iter, GFP_NOWAIT, IDA_MAX);
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if (IS_ERR(slot)) {
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if (slot == ERR_PTR(-ENOMEM))
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return -EAGAIN;
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return PTR_ERR(slot);
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}
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}
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if (iter.index > index) {
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bit = 0;
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ebit = RADIX_TREE_EXCEPTIONAL_SHIFT;
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}
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new = iter.index * IDA_BITMAP_BITS;
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bitmap = rcu_dereference_raw(*slot);
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if (radix_tree_exception(bitmap)) {
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unsigned long tmp = (unsigned long)bitmap;
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ebit = find_next_zero_bit(&tmp, BITS_PER_LONG, ebit);
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if (ebit < BITS_PER_LONG) {
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tmp |= 1UL << ebit;
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rcu_assign_pointer(*slot, (void *)tmp);
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*id = new + ebit - RADIX_TREE_EXCEPTIONAL_SHIFT;
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return 0;
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}
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bitmap = this_cpu_xchg(ida_bitmap, NULL);
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if (!bitmap)
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return -EAGAIN;
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memset(bitmap, 0, sizeof(*bitmap));
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bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
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rcu_assign_pointer(*slot, bitmap);
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}
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if (bitmap) {
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bit = find_next_zero_bit(bitmap->bitmap,
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IDA_BITMAP_BITS, bit);
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new += bit;
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if (new < 0)
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return -ENOSPC;
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if (bit == IDA_BITMAP_BITS)
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continue;
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__set_bit(bit, bitmap->bitmap);
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if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
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radix_tree_iter_tag_clear(root, &iter,
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IDR_FREE);
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} else {
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new += bit;
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if (new < 0)
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return -ENOSPC;
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if (ebit < BITS_PER_LONG) {
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bitmap = (void *)((1UL << ebit) |
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RADIX_TREE_EXCEPTIONAL_ENTRY);
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radix_tree_iter_replace(root, &iter, slot,
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bitmap);
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*id = new;
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return 0;
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}
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bitmap = this_cpu_xchg(ida_bitmap, NULL);
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if (!bitmap)
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return -EAGAIN;
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memset(bitmap, 0, sizeof(*bitmap));
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__set_bit(bit, bitmap->bitmap);
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radix_tree_iter_replace(root, &iter, slot, bitmap);
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}
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*id = new;
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return 0;
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}
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}
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EXPORT_SYMBOL(ida_get_new_above);
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/**
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* ida_remove - Free the given ID
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* @ida: ida handle
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* @id: ID to free
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*
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* This function should not be called at the same time as ida_get_new_above().
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*/
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void ida_remove(struct ida *ida, int id)
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{
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unsigned long index = id / IDA_BITMAP_BITS;
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unsigned offset = id % IDA_BITMAP_BITS;
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struct ida_bitmap *bitmap;
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unsigned long *btmp;
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struct radix_tree_iter iter;
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void __rcu **slot;
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slot = radix_tree_iter_lookup(&ida->ida_rt, &iter, index);
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if (!slot)
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goto err;
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bitmap = rcu_dereference_raw(*slot);
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if (radix_tree_exception(bitmap)) {
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btmp = (unsigned long *)slot;
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offset += RADIX_TREE_EXCEPTIONAL_SHIFT;
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if (offset >= BITS_PER_LONG)
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goto err;
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} else {
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btmp = bitmap->bitmap;
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}
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if (!test_bit(offset, btmp))
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goto err;
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__clear_bit(offset, btmp);
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radix_tree_iter_tag_set(&ida->ida_rt, &iter, IDR_FREE);
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if (radix_tree_exception(bitmap)) {
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if (rcu_dereference_raw(*slot) ==
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(void *)RADIX_TREE_EXCEPTIONAL_ENTRY)
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radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
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} else if (bitmap_empty(btmp, IDA_BITMAP_BITS)) {
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kfree(bitmap);
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radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
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}
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return;
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err:
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WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
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}
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EXPORT_SYMBOL(ida_remove);
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/**
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* ida_destroy - Free the contents of an ida
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* @ida: ida handle
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*
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* Calling this function releases all resources associated with an IDA. When
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* this call returns, the IDA is empty and can be reused or freed. The caller
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* should not allow ida_remove() or ida_get_new_above() to be called at the
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* same time.
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*/
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void ida_destroy(struct ida *ida)
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{
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struct radix_tree_iter iter;
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void __rcu **slot;
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radix_tree_for_each_slot(slot, &ida->ida_rt, &iter, 0) {
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struct ida_bitmap *bitmap = rcu_dereference_raw(*slot);
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if (!radix_tree_exception(bitmap))
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kfree(bitmap);
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radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
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}
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}
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EXPORT_SYMBOL(ida_destroy);
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/**
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* ida_simple_get - get a new id.
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* @ida: the (initialized) ida.
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* @start: the minimum id (inclusive, < 0x8000000)
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* @end: the maximum id (exclusive, < 0x8000000 or 0)
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* @gfp_mask: memory allocation flags
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*
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* Allocates an id in the range start <= id < end, or returns -ENOSPC.
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* On memory allocation failure, returns -ENOMEM.
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*
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* Compared to ida_get_new_above() this function does its own locking, and
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* should be used unless there are special requirements.
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*
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* Use ida_simple_remove() to get rid of an id.
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*/
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int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
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gfp_t gfp_mask)
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{
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int ret, id;
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unsigned int max;
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unsigned long flags;
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BUG_ON((int)start < 0);
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BUG_ON((int)end < 0);
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if (end == 0)
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max = 0x80000000;
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else {
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BUG_ON(end < start);
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max = end - 1;
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}
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again:
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if (!ida_pre_get(ida, gfp_mask))
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return -ENOMEM;
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spin_lock_irqsave(&simple_ida_lock, flags);
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ret = ida_get_new_above(ida, start, &id);
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if (!ret) {
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if (id > max) {
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ida_remove(ida, id);
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ret = -ENOSPC;
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} else {
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ret = id;
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}
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}
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spin_unlock_irqrestore(&simple_ida_lock, flags);
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if (unlikely(ret == -EAGAIN))
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goto again;
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return ret;
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}
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EXPORT_SYMBOL(ida_simple_get);
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/**
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* ida_simple_remove - remove an allocated id.
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* @ida: the (initialized) ida.
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* @id: the id returned by ida_simple_get.
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*
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* Use to release an id allocated with ida_simple_get().
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*
|
|
* Compared to ida_remove() this function does its own locking, and should be
|
|
* used unless there are special requirements.
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|
*/
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|
void ida_simple_remove(struct ida *ida, unsigned int id)
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|
{
|
|
unsigned long flags;
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|
|
|
BUG_ON((int)id < 0);
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|
spin_lock_irqsave(&simple_ida_lock, flags);
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|
ida_remove(ida, id);
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|
spin_unlock_irqrestore(&simple_ida_lock, flags);
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|
}
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|
EXPORT_SYMBOL(ida_simple_remove);
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