diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 15eab63286ed184f314c1c577276233d38c6b701..7f740f675b96c3605c7a96dee7619461c87a73fd 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -275,6 +275,8 @@ struct xarray {
void xa_init_flags(struct xarray *, gfp_t flags);
void *xa_load(struct xarray *, unsigned long index);
void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
+void *xa_cmpxchg(struct xarray *, unsigned long index,
+ void *old, void *entry, gfp_t);
bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t);
void xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
void xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
@@ -334,6 +336,34 @@ static inline void *xa_erase(struct xarray *xa, unsigned long index)
return xa_store(xa, index, NULL, 0);
}
+/**
+ * xa_insert() - Store this entry in the XArray unless another entry is
+ * already present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * If you would rather see the existing entry in the array, use xa_cmpxchg().
+ * This function is for users who don't care what the entry is, only that
+ * one is present.
+ *
+ * Context: Process context. Takes and releases the xa_lock.
+ * May sleep if the @gfp flags permit.
+ * Return: 0 if the store succeeded. -EEXIST if another entry was present.
+ * -ENOMEM if memory could not be allocated.
+ */
+static inline int xa_insert(struct xarray *xa, unsigned long index,
+ void *entry, gfp_t gfp)
+{
+ void *curr = xa_cmpxchg(xa, index, NULL, entry, gfp);
+ if (!curr)
+ return 0;
+ if (xa_is_err(curr))
+ return xa_err(curr);
+ return -EEXIST;
+}
+
#define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
#define xa_lock(xa) spin_lock(&(xa)->xa_lock)
#define xa_unlock(xa) spin_unlock(&(xa)->xa_lock)
@@ -355,9 +385,39 @@ static inline void *xa_erase(struct xarray *xa, unsigned long index)
*/
void *__xa_erase(struct xarray *, unsigned long index);
void *__xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
+void *__xa_cmpxchg(struct xarray *, unsigned long index, void *old,
+ void *entry, gfp_t);
void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
+/**
+ * __xa_insert() - Store this entry in the XArray unless another entry is
+ * already present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * If you would rather see the existing entry in the array, use __xa_cmpxchg().
+ * This function is for users who don't care what the entry is, only that
+ * one is present.
+ *
+ * Context: Any context. Expects xa_lock to be held on entry. May
+ * release and reacquire xa_lock if the @gfp flags permit.
+ * Return: 0 if the store succeeded. -EEXIST if another entry was present.
+ * -ENOMEM if memory could not be allocated.
+ */
+static inline int __xa_insert(struct xarray *xa, unsigned long index,
+ void *entry, gfp_t gfp)
+{
+ void *curr = __xa_cmpxchg(xa, index, NULL, entry, gfp);
+ if (!curr)
+ return 0;
+ if (xa_is_err(curr))
+ return xa_err(curr);
+ return -EEXIST;
+}
+
/**
* xa_erase_bh() - Erase this entry from the XArray.
* @xa: XArray.
diff --git a/lib/test_xarray.c b/lib/test_xarray.c
index b711030fbc32d420c56aa308a23a99822b186594..fb472258b639dbb822157e3e525e2a61d51a7088 100644
--- a/lib/test_xarray.c
+++ b/lib/test_xarray.c
@@ -198,6 +198,25 @@ static noinline void check_xa_shrink(struct xarray *xa)
XA_BUG_ON(xa, !xa_empty(xa));
}
+static noinline void check_cmpxchg(struct xarray *xa)
+{
+ void *FIVE = xa_mk_value(5);
+ void *SIX = xa_mk_value(6);
+ void *LOTS = xa_mk_value(12345678);
+
+ XA_BUG_ON(xa, !xa_empty(xa));
+ XA_BUG_ON(xa, xa_store_index(xa, 12345678, GFP_KERNEL) != NULL);
+ XA_BUG_ON(xa, xa_insert(xa, 12345678, xa, GFP_KERNEL) != -EEXIST);
+ XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, SIX, FIVE, GFP_KERNEL) != LOTS);
+ XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, LOTS, FIVE, GFP_KERNEL) != LOTS);
+ XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, FIVE, LOTS, GFP_KERNEL) != FIVE);
+ XA_BUG_ON(xa, xa_cmpxchg(xa, 5, FIVE, NULL, GFP_KERNEL) != NULL);
+ XA_BUG_ON(xa, xa_cmpxchg(xa, 5, NULL, FIVE, GFP_KERNEL) != NULL);
+ xa_erase_index(xa, 12345678);
+ xa_erase_index(xa, 5);
+ XA_BUG_ON(xa, !xa_empty(xa));
+}
+
static noinline void check_multi_store(struct xarray *xa)
{
#ifdef CONFIG_XARRAY_MULTI
@@ -274,6 +293,7 @@ static int xarray_checks(void)
check_xa_load(&array);
check_xa_mark(&array);
check_xa_shrink(&array);
+ check_cmpxchg(&array);
check_multi_store(&array);
printk("XArray: %u of %u tests passed\n", tests_passed, tests_run);
diff --git a/lib/xarray.c b/lib/xarray.c
index 4596a95ed9cda761dc0db79a9ef629ce5f5fcd21..2ba5a98ec6186e4d22da97d9c86a2b03e3f18bc1 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -975,6 +975,77 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
}
EXPORT_SYMBOL(__xa_store);
+/**
+ * xa_cmpxchg() - Conditionally replace an entry in the XArray.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @old: Old value to test against.
+ * @entry: New value to place in array.
+ * @gfp: Memory allocation flags.
+ *
+ * If the entry at @index is the same as @old, replace it with @entry.
+ * If the return value is equal to @old, then the exchange was successful.
+ *
+ * Context: Process context. Takes and releases the xa_lock. May sleep
+ * if the @gfp flags permit.
+ * Return: The old value at this index or xa_err() if an error happened.
+ */
+void *xa_cmpxchg(struct xarray *xa, unsigned long index,
+ void *old, void *entry, gfp_t gfp)
+{
+ XA_STATE(xas, xa, index);
+ void *curr;
+
+ if (WARN_ON_ONCE(xa_is_internal(entry)))
+ return XA_ERROR(-EINVAL);
+
+ do {
+ xas_lock(&xas);
+ curr = xas_load(&xas);
+ if (curr == old)
+ xas_store(&xas, entry);
+ xas_unlock(&xas);
+ } while (xas_nomem(&xas, gfp));
+
+ return xas_result(&xas, curr);
+}
+EXPORT_SYMBOL(xa_cmpxchg);
+
+/**
+ * __xa_cmpxchg() - Store this entry in the XArray.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @old: Old value to test against.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * You must already be holding the xa_lock when calling this function.
+ * It will drop the lock if needed to allocate memory, and then reacquire
+ * it afterwards.
+ *
+ * Context: Any context. Expects xa_lock to be held on entry. May
+ * release and reacquire xa_lock if @gfp flags permit.
+ * Return: The old entry at this index or xa_err() if an error happened.
+ */
+void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
+ void *old, void *entry, gfp_t gfp)
+{
+ XA_STATE(xas, xa, index);
+ void *curr;
+
+ if (WARN_ON_ONCE(xa_is_internal(entry)))
+ return XA_ERROR(-EINVAL);
+
+ do {
+ curr = xas_load(&xas);
+ if (curr == old)
+ xas_store(&xas, entry);
+ } while (__xas_nomem(&xas, gfp));
+
+ return xas_result(&xas, curr);
+}
+EXPORT_SYMBOL(__xa_cmpxchg);
+
/**
* __xa_set_mark() - Set this mark on this entry while locked.
* @xa: XArray.