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authorMatthew Wilcox <willy@infradead.org>2018-10-26 21:43:22 +0300
committerMatthew Wilcox <willy@infradead.org>2019-02-06 21:13:24 +0300
commit3ccaf57a6a63ad171a951dcaddffc453b2414c7b (patch)
treefc2202432a5b50ee5507a2e240b439b2993c2c3f /include/linux/xarray.h
parentfd9dc93e36231fb6d520e0edd467058fad4fd12d (diff)
downloadlinux-3ccaf57a6a63ad171a951dcaddffc453b2414c7b.tar.xz
XArray: Add support for 1s-based allocation
A lot of places want to allocate IDs starting at 1 instead of 0. While the xa_alloc() API supports this, it's not very efficient if lots of IDs are allocated, due to having to walk down to the bottom of the tree to see if ID 1 is available, then all the way over to the next non-allocated ID. This method marks ID 0 as being occupied which wastes one slot in the XArray, but preserves xa_empty() as working. Signed-off-by: Matthew Wilcox <willy@infradead.org>
Diffstat (limited to 'include/linux/xarray.h')
-rw-r--r--include/linux/xarray.h14
1 files changed, 13 insertions, 1 deletions
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 57cf35c4d094..99dd0838b4ba 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -220,10 +220,13 @@ enum xa_lock_type {
#define XA_FLAGS_LOCK_IRQ ((__force gfp_t)XA_LOCK_IRQ)
#define XA_FLAGS_LOCK_BH ((__force gfp_t)XA_LOCK_BH)
#define XA_FLAGS_TRACK_FREE ((__force gfp_t)4U)
+#define XA_FLAGS_ZERO_BUSY ((__force gfp_t)8U)
#define XA_FLAGS_MARK(mark) ((__force gfp_t)((1U << __GFP_BITS_SHIFT) << \
(__force unsigned)(mark)))
+/* ALLOC is for a normal 0-based alloc. ALLOC1 is for an 1-based alloc */
#define XA_FLAGS_ALLOC (XA_FLAGS_TRACK_FREE | XA_FLAGS_MARK(XA_FREE_MARK))
+#define XA_FLAGS_ALLOC1 (XA_FLAGS_TRACK_FREE | XA_FLAGS_ZERO_BUSY)
/**
* struct xarray - The anchor of the XArray.
@@ -279,7 +282,7 @@ struct xarray {
#define DEFINE_XARRAY(name) DEFINE_XARRAY_FLAGS(name, 0)
/**
- * DEFINE_XARRAY_ALLOC() - Define an XArray which can allocate IDs.
+ * DEFINE_XARRAY_ALLOC() - Define an XArray which allocates IDs starting at 0.
* @name: A string that names your XArray.
*
* This is intended for file scope definitions of allocating XArrays.
@@ -287,6 +290,15 @@ struct xarray {
*/
#define DEFINE_XARRAY_ALLOC(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC)
+/**
+ * DEFINE_XARRAY_ALLOC1() - Define an XArray which allocates IDs starting at 1.
+ * @name: A string that names your XArray.
+ *
+ * This is intended for file scope definitions of allocating XArrays.
+ * See also DEFINE_XARRAY().
+ */
+#define DEFINE_XARRAY_ALLOC1(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC1)
+
void *xa_load(struct xarray *, unsigned long index);
void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
void *xa_erase(struct xarray *, unsigned long index);