idr: Remove idr_alloc_ext
It has no more users, so remove it. Move idr_alloc() back into idr.c, move the guts of idr_alloc_cmn() into idr_alloc_u32(), remove the wrappers around idr_get_free_cmn() and rename it to idr_get_free(). While there is now no interface to allocate IDs larger than a u32, the IDR internals remain ready to handle a larger ID should a need arise. These changes make it possible to provide the guarantee that, if the nextid pointer points into the object, the object's ID will be initialised before a concurrent lookup can find the object. Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
This commit is contained in:
Matthew Wilcox
parent
f730cb93db
commit
460488c58c
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@ -15,7 +15,6 @@
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#include <linux/radix-tree.h>
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#include <linux/gfp.h>
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#include <linux/percpu.h>
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#include <linux/bug.h>
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struct idr {
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struct radix_tree_root idr_rt;
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@ -82,55 +81,7 @@ static inline void idr_set_cursor(struct idr *idr, unsigned int val)
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void idr_preload(gfp_t gfp_mask);
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int idr_alloc_cmn(struct idr *idr, void *ptr, unsigned long *index,
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unsigned long start, unsigned long end, gfp_t gfp,
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bool ext);
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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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static inline int idr_alloc(struct idr *idr, void *ptr,
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int start, int end, gfp_t gfp)
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{
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unsigned long id;
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int ret;
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if (WARN_ON_ONCE(start < 0))
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return -EINVAL;
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ret = idr_alloc_cmn(idr, ptr, &id, start, end, gfp, false);
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if (ret)
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return ret;
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return id;
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}
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static inline int idr_alloc_ext(struct idr *idr, void *ptr,
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unsigned long *index,
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unsigned long start,
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unsigned long end,
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gfp_t gfp)
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{
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return idr_alloc_cmn(idr, ptr, index, start, end, gfp, true);
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}
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int idr_alloc(struct idr *, void *, int start, int end, gfp_t);
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int __must_check idr_alloc_u32(struct idr *, void *ptr, u32 *nextid,
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unsigned long max, gfp_t);
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int idr_alloc_cyclic(struct idr *, void *entry, int start, int end, gfp_t);
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@ -356,24 +356,9 @@ int radix_tree_split(struct radix_tree_root *, unsigned long index,
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int radix_tree_join(struct radix_tree_root *, unsigned long index,
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unsigned new_order, void *);
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void __rcu **idr_get_free_cmn(struct radix_tree_root *root,
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void __rcu **idr_get_free(struct radix_tree_root *root,
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struct radix_tree_iter *iter, gfp_t gfp,
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unsigned long max);
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static inline void __rcu **idr_get_free(struct radix_tree_root *root,
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struct radix_tree_iter *iter,
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gfp_t gfp,
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int end)
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{
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return idr_get_free_cmn(root, iter, gfp, end > 0 ? end - 1 : INT_MAX);
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}
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static inline void __rcu **idr_get_free_ext(struct radix_tree_root *root,
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struct radix_tree_iter *iter,
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gfp_t gfp,
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unsigned long end)
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{
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return idr_get_free_cmn(root, iter, gfp, end - 1);
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}
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enum {
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RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */
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126
lib/idr.c
126
lib/idr.c
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@ -1,4 +1,5 @@
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#include <linux/bitmap.h>
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#include <linux/bug.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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@ -17,7 +18,9 @@ static DEFINE_SPINLOCK(simple_ida_lock);
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*
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* Allocates an unused ID in the range specified by @nextid and @max.
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* Note that @max is inclusive whereas the @end parameter to idr_alloc()
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* is exclusive.
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* is exclusive. The new ID is assigned to @nextid before the pointer
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* is inserted into the IDR, so if @nextid points into the object pointed
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* to by @ptr, a concurrent lookup will not find an uninitialised ID.
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*
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* The caller should provide their own locking to ensure that two
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* concurrent modifications to the IDR are not possible. Read-only
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@ -30,67 +33,104 @@ static DEFINE_SPINLOCK(simple_ida_lock);
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*/
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int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
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unsigned long max, gfp_t gfp)
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{
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unsigned long tmp = *nextid;
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int ret = idr_alloc_ext(idr, ptr, &tmp, tmp, max + 1, gfp);
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*nextid = tmp;
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return ret;
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}
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EXPORT_SYMBOL_GPL(idr_alloc_u32);
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int idr_alloc_cmn(struct idr *idr, void *ptr, unsigned long *index,
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unsigned long start, unsigned long end, gfp_t gfp,
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bool ext)
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{
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struct radix_tree_iter iter;
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void __rcu **slot;
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if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
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return -EINVAL;
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if (WARN_ON_ONCE(!(idr->idr_rt.gfp_mask & ROOT_IS_IDR)))
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idr->idr_rt.gfp_mask |= IDR_RT_MARKER;
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radix_tree_iter_init(&iter, start);
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if (ext)
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slot = idr_get_free_ext(&idr->idr_rt, &iter, gfp, end);
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else
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slot = idr_get_free(&idr->idr_rt, &iter, gfp, end);
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radix_tree_iter_init(&iter, *nextid);
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slot = idr_get_free(&idr->idr_rt, &iter, gfp, max);
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if (IS_ERR(slot))
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return PTR_ERR(slot);
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*nextid = iter.index;
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/* there is a memory barrier inside radix_tree_iter_replace() */
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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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if (index)
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*index = iter.index;
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return 0;
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}
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EXPORT_SYMBOL_GPL(idr_alloc_cmn);
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EXPORT_SYMBOL_GPL(idr_alloc_u32);
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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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* 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 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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* Allocates an unused ID in the range specified by @start and @end. If
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* @end is <= 0, it is treated as one larger than %INT_MAX. This allows
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* callers to use @start + N as @end as long as N is within integer range.
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*
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* The caller should provide their own locking to ensure that two
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* concurrent modifications to the IDR are not possible. Read-only
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* accesses to the IDR may be done under the RCU read lock or may
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* exclude simultaneous writers.
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*
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* Return: The newly allocated ID, -ENOMEM if memory allocation failed,
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* or -ENOSPC if no free IDs could be found.
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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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u32 id = start;
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int ret;
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if (WARN_ON_ONCE(start < 0))
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return -EINVAL;
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ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp);
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if (ret)
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return ret;
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return id;
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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 an ID cyclically.
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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 specified by @nextid and @end. If
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* @end is <= 0, it is treated as one larger than %INT_MAX. This allows
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* callers to use @start + N as @end as long as N is within integer range.
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* The search for an unused ID will start at the last ID allocated and will
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* wrap around to @start if no free IDs are found before reaching @end.
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*
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* The caller should provide their own locking to ensure that two
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* concurrent modifications to the IDR are not possible. Read-only
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* accesses to the IDR may be done under the RCU read lock or may
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* exclude simultaneous writers.
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*
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* Return: The newly allocated ID, -ENOMEM if memory allocation failed,
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* or -ENOSPC if no free IDs could be found.
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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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u32 id = idr->idr_next;
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int err, max = end > 0 ? end - 1 : INT_MAX;
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if (curr < start)
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curr = start;
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if ((int)id < start)
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id = 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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err = idr_alloc_u32(idr, ptr, &id, max, gfp);
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if ((err == -ENOSPC) && (id > start)) {
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id = start;
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err = idr_alloc_u32(idr, ptr, &id, max, gfp);
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}
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if (err)
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return err;
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idr->idr_next = id + 1;
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return id;
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}
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EXPORT_SYMBOL(idr_alloc_cyclic);
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@ -167,10 +207,10 @@ void *idr_get_next_ext(struct idr *idr, unsigned long *nextid)
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EXPORT_SYMBOL(idr_get_next_ext);
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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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* 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: ID to change.
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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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@ -257,7 +297,7 @@ EXPORT_SYMBOL(idr_replace);
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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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#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS - 1)
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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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@ -24,6 +24,7 @@
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#include <linux/bitmap.h>
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#include <linux/bitops.h>
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#include <linux/bug.h>
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#include <linux/cpu.h>
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#include <linux/errno.h>
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#include <linux/export.h>
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@ -2135,7 +2136,7 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
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}
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EXPORT_SYMBOL(ida_pre_get);
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void __rcu **idr_get_free_cmn(struct radix_tree_root *root,
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void __rcu **idr_get_free(struct radix_tree_root *root,
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struct radix_tree_iter *iter, gfp_t gfp,
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unsigned long max)
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{
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@ -215,6 +215,23 @@ void idr_checks(void)
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assert(idr_is_empty(&idr));
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idr_set_cursor(&idr, INT_MAX - 3UL);
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for (i = INT_MAX - 3UL; i < INT_MAX + 3UL; i++) {
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struct item *item;
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unsigned int id;
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if (i <= INT_MAX)
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item = item_create(i, 0);
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else
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item = item_create(i - INT_MAX - 1, 0);
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id = idr_alloc_cyclic(&idr, item, 0, 0, GFP_KERNEL);
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assert(id == item->index);
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}
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idr_for_each(&idr, item_idr_free, &idr);
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idr_destroy(&idr);
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assert(idr_is_empty(&idr));
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for (i = 1; i < 10000; i++) {
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struct item *item = item_create(i, 0);
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assert(idr_alloc(&idr, item, 1, 20000, GFP_KERNEL) == i);
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