XArray: Permit storing 2-byte-aligned pointers

On m68k, statically allocated pointers may only be two-byte aligned.
This clashes with the XArray's method for tagging internal pointers.
Permit storing these pointers in single slots (ie not in multislots).

Signed-off-by: Matthew Wilcox <willy@infradead.org>

1 files changed, 13 insertions, 9 deletions

diff --git a/lib/xarray.c b/lib/xarray.c
index dda6026d202e..bffa26b1f0d6 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -232,6 +232,8 @@ void *xas_load(struct xa_state *xas)
                 if (xas->xa_shift > node->shift)
                         break;
                 entry = xas_descend(xas, node);
+                if (node->shift == 0)
+                        break;
         }
         return entry;
 }
@@ -506,7 +508,7 @@ static void xas_free_nodes(struct xa_state *xas, struct xa_node *top)
         for (;;) {
                 void *entry = xa_entry_locked(xas->xa, node, offset);
 
-                if (xa_is_node(entry)) {
+                if (node->shift && xa_is_node(entry)) {
                         node = xa_to_node(entry);
                         offset = 0;
                         continue;
@@ -604,6 +606,7 @@ static int xas_expand(struct xa_state *xas, void *head)
 /*
  * xas_create() - Create a slot to store an entry in.
  * @xas: XArray operation state.
+ * @allow_root: %true if we can store the entry in the root directly
  *
  * Most users will not need to call this function directly, as it is called
  * by xas_store().  It is useful for doing conditional store operations
@@ -613,7 +616,7 @@ static int xas_expand(struct xa_state *xas, void *head)
  * If the slot was newly created, returns %NULL.  If it failed to create the
  * slot, returns %NULL and indicates the error in @xas.
  */
-static void *xas_create(struct xa_state *xas)
+static void *xas_create(struct xa_state *xas, bool allow_root)
 {
         struct xarray *xa = xas->xa;
         void *entry;
@@ -628,6 +631,8 @@ static void *xas_create(struct xa_state *xas)
                 shift = xas_expand(xas, entry);
                 if (shift < 0)
                         return NULL;
+                if (!shift && !allow_root)
+                        shift = XA_CHUNK_SHIFT;
                 entry = xa_head_locked(xa);
                 slot = &xa->xa_head;
         } else if (xas_error(xas)) {
@@ -687,7 +692,7 @@ void xas_create_range(struct xa_state *xas)
         xas->xa_sibs = 0;
 
         for (;;) {
-                xas_create(xas);
+                xas_create(xas, true);
                 if (xas_error(xas))
                         goto restore;
                 if (xas->xa_index <= (index | XA_CHUNK_MASK))
@@ -754,7 +759,7 @@ void *xas_store(struct xa_state *xas, void *entry)
         bool value = xa_is_value(entry);
 
         if (entry)
-                first = xas_create(xas);
+                first = xas_create(xas, !xa_is_node(entry));
         else
                 first = xas_load(xas);
 
@@ -1279,7 +1284,6 @@ static void *xas_result(struct xa_state *xas, void *curr)
 {
         if (xa_is_zero(curr))
                 return NULL;
-        XA_NODE_BUG_ON(xas->xa_node, xa_is_internal(curr));
         if (xas_error(xas))
                 curr = xas->xa_node;
         return curr;
@@ -1349,7 +1353,7 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
         XA_STATE(xas, xa, index);
         void *curr;
 
-        if (WARN_ON_ONCE(xa_is_internal(entry)))
+        if (WARN_ON_ONCE(xa_is_advanced(entry)))
                 return XA_ERROR(-EINVAL);
         if (xa_track_free(xa) && !entry)
                 entry = XA_ZERO_ENTRY;
@@ -1415,7 +1419,7 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
         XA_STATE(xas, xa, index);
         void *curr;
 
-        if (WARN_ON_ONCE(xa_is_internal(entry)))
+        if (WARN_ON_ONCE(xa_is_advanced(entry)))
                 return XA_ERROR(-EINVAL);
         if (xa_track_free(xa) && !entry)
                 entry = XA_ZERO_ENTRY;
@@ -1538,7 +1542,7 @@ void *xa_store_range(struct xarray *xa, unsigned long first,
                         if (last + 1)
                                 order = __ffs(last + 1);
                         xas_set_order(&xas, last, order);
-                        xas_create(&xas);
+                        xas_create(&xas, true);
                         if (xas_error(&xas))
                                 goto unlock;
                 }
@@ -1580,7 +1584,7 @@ int __xa_alloc(struct xarray *xa, u32 *id, u32 max, void *entry, gfp_t gfp)
         XA_STATE(xas, xa, 0);
         int err;
 
-        if (WARN_ON_ONCE(xa_is_internal(entry)))
+        if (WARN_ON_ONCE(xa_is_advanced(entry)))
                 return -EINVAL;
         if (WARN_ON_ONCE(!xa_track_free(xa)))
                 return -EINVAL;