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[PATCH] lib: add idr_replace

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This patch adds idr_replace() to replace an existing pointer in a single
operation.

Device-mapper will use this to update the pointer it stored against a given
id.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Jeff Mahoney 2006-06-26 00:27:19 -07:00 committed by Linus Torvalds
parent c51c275249
commit 5806f07cd2
2 changed files with 44 additions and 0 deletions
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1
include/linux/idr.h
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@ -78,6 +78,7 @@ void *idr_find(struct idr *idp, int id);
int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
int idr_get_new(struct idr *idp, void *ptr, int *id);
int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
void *idr_replace(struct idr *idp, void *ptr, int id);
void idr_remove(struct idr *idp, int id);
void idr_destroy(struct idr *idp);
void idr_init(struct idr *idp);

43
lib/idr.c
View File

@ -29,6 +29,7 @@
#include <linux/init.h>
#include <linux/module.h>
#endif
#include <linux/err.h>
#include <linux/string.h>
#include <linux/idr.h>
@ -398,6 +399,48 @@ void *idr_find(struct idr *idp, int id)
}
EXPORT_SYMBOL(idr_find);
/**
* idr_replace - replace pointer for given id
* @idp: idr handle
* @ptr: pointer you want associated with the id
* @id: lookup key
*
* Replace the pointer registered with an id and return the old value.
* A -ENOENT return indicates that @id was not found.
* A -EINVAL return indicates that @id was not within valid constraints.
*
* The caller must serialize vs idr_find(), idr_get_new(), and idr_remove().
*/
void *idr_replace(struct idr *idp, void *ptr, int id)
{
int n;
struct idr_layer *p, *old_p;
n = idp->layers * IDR_BITS;
p = idp->top;
id &= MAX_ID_MASK;
if (id >= (1 << n))
return ERR_PTR(-EINVAL);
n -= IDR_BITS;
while ((n > 0) && p) {
p = p->ary[(id >> n) & IDR_MASK];
n -= IDR_BITS;
}
n = id & IDR_MASK;
if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
return ERR_PTR(-ENOENT);
old_p = p->ary[n];
p->ary[n] = ptr;
return old_p;
}
EXPORT_SYMBOL(idr_replace);
static void idr_cache_ctor(void * idr_layer, kmem_cache_t *idr_layer_cache,
unsigned long flags)
{