XArray: Handle NULL pointers differently for allocation

For allocating XArrays, it makes sense to distinguish beteen erasing an
entry and storing NULL.  Storing NULL keeps the index allocated with a
NULL pointer associated with it while xa_erase() frees the index.  Some
existing IDR users rely on this ability.

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

1 files changed, 10 insertions, 3 deletions

diff --git a/lib/xarray.c b/lib/xarray.c
index a9d28013f9dc..c3e2084aa313 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1382,10 +1382,12 @@ void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
 
         if (WARN_ON_ONCE(xa_is_internal(entry)))
                 return XA_ERROR(-EINVAL);
+        if (xa_track_free(xa) && !entry)
+                entry = XA_ZERO_ENTRY;
 
         do {
                 curr = xas_store(&xas, entry);
-                if (xa_track_free(xa) && entry)
+                if (xa_track_free(xa))
                         xas_clear_mark(&xas, XA_FREE_MARK);
         } while (__xas_nomem(&xas, gfp));
 
@@ -1446,6 +1448,8 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
 
         if (WARN_ON_ONCE(xa_is_internal(entry)))
                 return XA_ERROR(-EINVAL);
+        if (xa_track_free(xa) && !entry)
+                entry = XA_ZERO_ENTRY;
 
         do {
                 curr = xas_load(&xas);
@@ -1453,7 +1457,7 @@ void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
                         curr = NULL;
                 if (curr == old) {
                         xas_store(&xas, entry);
-                        if (xa_track_free(xa) && entry)
+                        if (xa_track_free(xa))
                                 xas_clear_mark(&xas, XA_FREE_MARK);
                 }
         } while (__xas_nomem(&xas, gfp));
@@ -1487,8 +1491,11 @@ int __xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp)
 
         do {
                 curr = xas_load(&xas);
-                if (!curr)
+                if (!curr) {
                         xas_store(&xas, XA_ZERO_ENTRY);
+                        if (xa_track_free(xa))
+                                xas_clear_mark(&xas, XA_FREE_MARK);
+                }
         } while (__xas_nomem(&xas, gfp));
 
         return xas_error(&xas);