[PATCH] lib: add idr_replace
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>
diff --git a/lib/idr.c b/lib/idr.c
index de19030..4d09681 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -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 @@
}
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)
{