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idr: Remove idr_alloc_ext

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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 2017-11-28 15:16:24 -05:00
parent f730cb93db
commit 460488c58c
5 changed files with 104 additions and 110 deletions
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51
include/linux/idr.h
View File

@ -15,7 +15,6 @@
#include <linux/radix-tree.h>
#include <linux/gfp.h>
#include <linux/percpu.h>
#include <linux/bug.h>
struct idr {
struct radix_tree_root idr_rt;
@ -82,55 +81,7 @@ static inline void idr_set_cursor(struct idr *idr, unsigned int val)
void idr_preload(gfp_t gfp_mask);
int idr_alloc_cmn(struct idr *idr, void *ptr, unsigned long *index,
unsigned long start, unsigned long end, gfp_t gfp,
bool ext);
/**
* 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 [start, end). Returns -ENOSPC
* if there are no unused IDs in that range.
*
* Note that @end is treated as max when <= 0. This is to always allow
* using @start + N as @end as long as N is inside integer range.
*
* Simultaneous modifications to the @idr are not allowed and should be
* prevented by the user, usually with a lock. idr_alloc() may be called
* concurrently with read-only accesses to the @idr, such as idr_find() and
* idr_for_each_entry().
*/
static inline int idr_alloc(struct idr *idr, void *ptr,
int start, int end, gfp_t gfp)
{
unsigned long id;
int ret;
if (WARN_ON_ONCE(start < 0))
return -EINVAL;
ret = idr_alloc_cmn(idr, ptr, &id, start, end, gfp, false);
if (ret)
return ret;
return id;
}
static inline int idr_alloc_ext(struct idr *idr, void *ptr,
unsigned long *index,
unsigned long start,
unsigned long end,
gfp_t gfp)
{
return idr_alloc_cmn(idr, ptr, index, start, end, gfp, true);
}
int idr_alloc(struct idr *, void *, int start, int end, gfp_t);
int __must_check idr_alloc_u32(struct idr *, void *ptr, u32 *nextid,
unsigned long max, gfp_t);
int idr_alloc_cyclic(struct idr *, void *entry, int start, int end, gfp_t);

17
include/linux/radix-tree.h
View File

@ -356,24 +356,9 @@ int radix_tree_split(struct radix_tree_root *, unsigned long index,
int radix_tree_join(struct radix_tree_root *, unsigned long index,
unsigned new_order, void *);
void __rcu **idr_get_free_cmn(struct radix_tree_root *root,
void __rcu **idr_get_free(struct radix_tree_root *root,
struct radix_tree_iter *iter, gfp_t gfp,
unsigned long max);
static inline void __rcu **idr_get_free(struct radix_tree_root *root,
struct radix_tree_iter *iter,
gfp_t gfp,
int end)
{
return idr_get_free_cmn(root, iter, gfp, end > 0 ? end - 1 : INT_MAX);
}
static inline void __rcu **idr_get_free_ext(struct radix_tree_root *root,
struct radix_tree_iter *iter,
gfp_t gfp,
unsigned long end)
{
return idr_get_free_cmn(root, iter, gfp, end - 1);
}
enum {
RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */

126
lib/idr.c
View File

@ -1,4 +1,5 @@
#include <linux/bitmap.h>
#include <linux/bug.h>
#include <linux/export.h>
#include <linux/idr.h>
#include <linux/slab.h>
@ -17,7 +18,9 @@ static DEFINE_SPINLOCK(simple_ida_lock);
*
* 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.
* 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
@ -30,67 +33,104 @@ static DEFINE_SPINLOCK(simple_ida_lock);
*/
int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,
unsigned long max, gfp_t gfp)
{
unsigned long tmp = *nextid;
int ret = idr_alloc_ext(idr, ptr, &tmp, tmp, max + 1, gfp);
*nextid = tmp;
return ret;
}
EXPORT_SYMBOL_GPL(idr_alloc_u32);
int idr_alloc_cmn(struct idr *idr, void *ptr, unsigned long *index,
unsigned long start, unsigned long end, gfp_t gfp,
bool ext)
{
struct radix_tree_iter iter;
void __rcu **slot;
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;
radix_tree_iter_init(&iter, start);
if (ext)
slot = idr_get_free_ext(&idr->idr_rt, &iter, gfp, end);
else
slot = idr_get_free(&idr->idr_rt, &iter, gfp, end);
radix_tree_iter_init(&iter, *nextid);
slot = idr_get_free(&idr->idr_rt, &iter, gfp, max);
if (IS_ERR(slot))
return PTR_ERR(slot);
*nextid = iter.index;
/* 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);
if (index)
*index = iter.index;
return 0;
}
EXPORT_SYMBOL_GPL(idr_alloc_cmn);
EXPORT_SYMBOL_GPL(idr_alloc_u32);
/**
* idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
* @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
* 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 ID larger than the last ID allocated if one is available.
* If not, it will attempt to allocate the smallest ID that is larger or
* equal to @start.
* 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)
{
int id, curr = idr->idr_next;
u32 id = idr->idr_next;
int err, max = end > 0 ? end - 1 : INT_MAX;
if (curr < start)
curr = start;
if ((int)id < start)
id = start;
id = idr_alloc(idr, ptr, curr, end, gfp);
if ((id == -ENOSPC) && (curr > start))
id = idr_alloc(idr, ptr, start, curr, gfp);
if (id >= 0)
idr->idr_next = id + 1U;
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);
@ -167,10 +207,10 @@ void *idr_get_next_ext(struct idr *idr, unsigned long *nextid)
EXPORT_SYMBOL(idr_get_next_ext);
/**
* idr_replace - replace pointer for given id
* @idr: idr handle
* @ptr: New pointer to associate with the ID
* @id: Lookup key
* 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
@ -257,7 +297,7 @@ EXPORT_SYMBOL(idr_replace);
* bitmap, which is excessive.
*/
#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS)
#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS - 1)
/**
* ida_get_new_above - allocate new ID above or equal to a start id

3
lib/radix-tree.c
View File

@ -24,6 +24,7 @@
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/cpu.h>
#include <linux/errno.h>
#include <linux/export.h>
@ -2135,7 +2136,7 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
}
EXPORT_SYMBOL(ida_pre_get);
void __rcu **idr_get_free_cmn(struct radix_tree_root *root,
void __rcu **idr_get_free(struct radix_tree_root *root,
struct radix_tree_iter *iter, gfp_t gfp,
unsigned long max)
{

17
tools/testing/radix-tree/idr-test.c
View File

@ -215,6 +215,23 @@ void idr_checks(void)
assert(idr_is_empty(&idr));
idr_set_cursor(&idr, INT_MAX - 3UL);
for (i = INT_MAX - 3UL; i < INT_MAX + 3UL; i++) {
struct item *item;
unsigned int id;
if (i <= INT_MAX)
item = item_create(i, 0);
else
item = item_create(i - INT_MAX - 1, 0);
id = idr_alloc_cyclic(&idr, item, 0, 0, GFP_KERNEL);
assert(id == item->index);
}
idr_for_each(&idr, item_idr_free, &idr);
idr_destroy(&idr);
assert(idr_is_empty(&idr));
for (i = 1; i < 10000; i++) {
struct item *item = item_create(i, 0);
assert(idr_alloc(&idr, item, 1, 20000, GFP_KERNEL) == i);