xarray: Add XArray conditional store operations

Like cmpxchg(), xa_cmpxchg will only store to the index if the current entry matches the old entry. It returns the current entry, which is usually more useful than the errno returned by radix_tree_insert(). For the users who really only want the errno, the xa_insert() wrapper provides a more convenient calling convention.

Matthew Wilcox committed 9 years ago

Commit 41aec911 parent 58d6ea33 files · +151 −0Browse files

Unified · Split

3 files

include/linux/xarray.h +60 −0
lib/test_xarray.c +20 −0
lib/xarray.c +71 −0

include/linux/xarray.h+60−0

@@ -275,6 +275,8 @@ struct xarray { · 274 unmodified lines
275	275	void xa_init_flags(struct xarray *, gfp_t flags);
276	276	void xa_load(struct xarray , unsigned long index);
277	277	void xa_store(struct xarray , unsigned long index, void *entry, gfp_t);
	278	+void xa_cmpxchg(struct xarray , unsigned long index,
	279	+ void old, void entry, gfp_t);
278	280	bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t);
279	281	void xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
280	282	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) · 53 unmodified lines
334	336	return xa_store(xa, index, NULL, 0);
335	337	}
336	338
	339	+/**
	340	+ * xa_insert() - Store this entry in the XArray unless another entry is
	341	+ * already present.
	342	+ * @xa: XArray.
	343	+ * @index: Index into array.
	344	+ * @entry: New entry.
	345	+ * @gfp: Memory allocation flags.
	346	+ *
	347	+ * If you would rather see the existing entry in the array, use xa_cmpxchg().
	348	+ * This function is for users who don't care what the entry is, only that
	349	+ * one is present.
	350	+ *
	351	+ * Context: Process context. Takes and releases the xa_lock.
	352	+ * May sleep if the @gfp flags permit.
	353	+ * Return: 0 if the store succeeded. -EEXIST if another entry was present.
	354	+ * -ENOMEM if memory could not be allocated.
	355	+ */
	356	+static inline int xa_insert(struct xarray *xa, unsigned long index,
	357	+ void *entry, gfp_t gfp)
	358	+{
	359	+ void *curr = xa_cmpxchg(xa, index, NULL, entry, gfp);
	360	+ if (!curr)
	361	+ return 0;
	362	+ if (xa_is_err(curr))
	363	+ return xa_err(curr);
	364	+ return -EEXIST;
	365	+}
	366	+
337	367	#define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
338	368	#define xa_lock(xa) spin_lock(&(xa)->xa_lock)
339	369	#define xa_unlock(xa) spin_unlock(&(xa)->xa_lock)
@@ -355,9 +385,39 @@ static inline void xa_erase(struct xarray xa, unsigned long index) · 15 unmodified lines
355	385	*/
356	386	void __xa_erase(struct xarray , unsigned long index);
357	387	void __xa_store(struct xarray , unsigned long index, void *entry, gfp_t);
	388	+void __xa_cmpxchg(struct xarray , unsigned long index, void *old,
	389	+ void *entry, gfp_t);
358	390	void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
359	391	void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
360	392
	393	+/**
	394	+ * __xa_insert() - Store this entry in the XArray unless another entry is
	395	+ * already present.
	396	+ * @xa: XArray.
	397	+ * @index: Index into array.
	398	+ * @entry: New entry.
	399	+ * @gfp: Memory allocation flags.
	400	+ *
	401	+ * If you would rather see the existing entry in the array, use __xa_cmpxchg().
	402	+ * This function is for users who don't care what the entry is, only that
	403	+ * one is present.
	404	+ *
	405	+ * Context: Any context. Expects xa_lock to be held on entry. May
	406	+ * release and reacquire xa_lock if the @gfp flags permit.
	407	+ * Return: 0 if the store succeeded. -EEXIST if another entry was present.
	408	+ * -ENOMEM if memory could not be allocated.
	409	+ */
	410	+static inline int __xa_insert(struct xarray *xa, unsigned long index,
	411	+ void *entry, gfp_t gfp)
	412	+{
	413	+ void *curr = __xa_cmpxchg(xa, index, NULL, entry, gfp);
	414	+ if (!curr)
	415	+ return 0;
	416	+ if (xa_is_err(curr))
	417	+ return xa_err(curr);
	418	+ return -EEXIST;
	419	+}
	420	+
361	421	/**
362	422	* xa_erase_bh() - Erase this entry from the XArray.
363	423	* @xa: XArray.

lib/test_xarray.c+20−0

@@ -198,6 +198,25 @@ static noinline void check_xa_shrink(struct xarray *xa) · 197 unmodified lines
198	198	XA_BUG_ON(xa, !xa_empty(xa));
199	199	}
200	200
	201	+static noinline void check_cmpxchg(struct xarray *xa)
	202	+{
	203	+ void *FIVE = xa_mk_value(5);
	204	+ void *SIX = xa_mk_value(6);
	205	+ void *LOTS = xa_mk_value(12345678);
	206	+
	207	+ XA_BUG_ON(xa, !xa_empty(xa));
	208	+ XA_BUG_ON(xa, xa_store_index(xa, 12345678, GFP_KERNEL) != NULL);
	209	+ XA_BUG_ON(xa, xa_insert(xa, 12345678, xa, GFP_KERNEL) != -EEXIST);
	210	+ XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, SIX, FIVE, GFP_KERNEL) != LOTS);
	211	+ XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, LOTS, FIVE, GFP_KERNEL) != LOTS);
	212	+ XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, FIVE, LOTS, GFP_KERNEL) != FIVE);
	213	+ XA_BUG_ON(xa, xa_cmpxchg(xa, 5, FIVE, NULL, GFP_KERNEL) != NULL);
	214	+ XA_BUG_ON(xa, xa_cmpxchg(xa, 5, NULL, FIVE, GFP_KERNEL) != NULL);
	215	+ xa_erase_index(xa, 12345678);
	216	+ xa_erase_index(xa, 5);
	217	+ XA_BUG_ON(xa, !xa_empty(xa));
	218	+}
	219	+
201	220	static noinline void check_multi_store(struct xarray *xa)
202	221	{
203	222	#ifdef CONFIG_XARRAY_MULTI
@@ -274,6 +293,7 @@ static int xarray_checks(void) · 70 unmodified lines
274	293	check_xa_load(&array);
275	294	check_xa_mark(&array);
276	295	check_xa_shrink(&array);
	296	+ check_cmpxchg(&array);
277	297	check_multi_store(&array);
278	298
279	299	printk("XArray: %u of %u tests passed\n", tests_passed, tests_run);

lib/xarray.c+71−0

@@ -975,6 +975,77 @@ void __xa_store(struct xarray xa, unsigned long index, void *entry, gfp_t gfp) · 974 unmodified lines
975	975	}
976	976	EXPORT_SYMBOL(__xa_store);
977	977
	978	+/**
	979	+ * xa_cmpxchg() - Conditionally replace an entry in the XArray.
	980	+ * @xa: XArray.
	981	+ * @index: Index into array.
	982	+ * @old: Old value to test against.
	983	+ * @entry: New value to place in array.
	984	+ * @gfp: Memory allocation flags.
	985	+ *
	986	+ * If the entry at @index is the same as @old, replace it with @entry.
	987	+ * If the return value is equal to @old, then the exchange was successful.
	988	+ *
	989	+ * Context: Process context. Takes and releases the xa_lock. May sleep
	990	+ * if the @gfp flags permit.
	991	+ * Return: The old value at this index or xa_err() if an error happened.
	992	+ */
	993	+void xa_cmpxchg(struct xarray xa, unsigned long index,
	994	+ void old, void entry, gfp_t gfp)
	995	+{
	996	+ XA_STATE(xas, xa, index);
	997	+ void *curr;
	998	+
	999	+ if (WARN_ON_ONCE(xa_is_internal(entry)))
	1000	+ return XA_ERROR(-EINVAL);
	1001	+
	1002	+ do {
	1003	+ xas_lock(&xas);
	1004	+ curr = xas_load(&xas);
	1005	+ if (curr == old)
	1006	+ xas_store(&xas, entry);
	1007	+ xas_unlock(&xas);
	1008	+ } while (xas_nomem(&xas, gfp));
	1009	+
	1010	+ return xas_result(&xas, curr);
	1011	+}
	1012	+EXPORT_SYMBOL(xa_cmpxchg);
	1013	+
	1014	+/**
	1015	+ * __xa_cmpxchg() - Store this entry in the XArray.
	1016	+ * @xa: XArray.
	1017	+ * @index: Index into array.
	1018	+ * @old: Old value to test against.
	1019	+ * @entry: New entry.
	1020	+ * @gfp: Memory allocation flags.
	1021	+ *
	1022	+ * You must already be holding the xa_lock when calling this function.
	1023	+ * It will drop the lock if needed to allocate memory, and then reacquire
	1024	+ * it afterwards.
	1025	+ *
	1026	+ * Context: Any context. Expects xa_lock to be held on entry. May
	1027	+ * release and reacquire xa_lock if @gfp flags permit.
	1028	+ * Return: The old entry at this index or xa_err() if an error happened.
	1029	+ */
	1030	+void __xa_cmpxchg(struct xarray xa, unsigned long index,
	1031	+ void old, void entry, gfp_t gfp)
	1032	+{
	1033	+ XA_STATE(xas, xa, index);
	1034	+ void *curr;
	1035	+
	1036	+ if (WARN_ON_ONCE(xa_is_internal(entry)))
	1037	+ return XA_ERROR(-EINVAL);
	1038	+
	1039	+ do {
	1040	+ curr = xas_load(&xas);
	1041	+ if (curr == old)
	1042	+ xas_store(&xas, entry);
	1043	+ } while (__xas_nomem(&xas, gfp));
	1044	+
	1045	+ return xas_result(&xas, curr);
	1046	+}
	1047	+EXPORT_SYMBOL(__xa_cmpxchg);
	1048	+
978	1049	/**
979	1050	* __xa_set_mark() - Set this mark on this entry while locked.
980	1051	* @xa: XArray.

xarray: Add XArray conditional store operations

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