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authorMatthew Wilcox <mawilcox@microsoft.com>2017-11-28 15:16:24 -0500
committerMatthew Wilcox <mawilcox@microsoft.com>2018-02-06 16:41:28 -0500
commit460488c58ca8b9167463ac22ec9a2e33db351962 (patch)
treea96e67ae3ef9ae38662ddeda2f208f581ac4691f /lib/idr.c
parentf730cb93db8e640f95ba4acb339d5732e1721730 (diff)
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>
Diffstat (limited to 'lib/idr.c')
-rw-r--r--lib/idr.c128
1 files changed, 84 insertions, 44 deletions
diff --git a/lib/idr.c b/lib/idr.c
index 6d4ec2c2982b..c3f16307b908 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -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
@@ -31,66 +34,103 @@ 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
- *
- * 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.
+ * 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 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_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
+int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
{
- int id, curr = idr->idr_next;
+ u32 id = start;
+ int ret;
+
+ if (WARN_ON_ONCE(start < 0))
+ return -EINVAL;
- if (curr < start)
- curr = start;
+ ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp);
+ if (ret)
+ return ret;
- id = idr_alloc(idr, ptr, curr, end, gfp);
- if ((id == -ENOSPC) && (curr > start))
- id = idr_alloc(idr, ptr, start, curr, gfp);
+ return id;
+}
+EXPORT_SYMBOL_GPL(idr_alloc);
- if (id >= 0)
- idr->idr_next = id + 1U;
+/**
+ * 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)
+{
+ u32 id = idr->idr_next;
+ int err, max = end > 0 ? end - 1 : INT_MAX;
+ if ((int)id < start)
+ id = start;
+
+ 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