XArray: Honour reserved entries in xa_insert

xa_insert() should treat reserved entries as occupied, not as available.
Also, it should treat requests to insert a NULL pointer as a request
to reserve the slot.  Add xa_insert_bh() and xa_insert_irq() for
completeness.

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

1 files changed, 9 insertions, 6 deletions

diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst
index 6a6d67acaf69..5d54b27c6eba 100644
--- a/Documentation/core-api/xarray.rst
+++ b/Documentation/core-api/xarray.rst
@@ -108,12 +108,13 @@ some, but not all of the other indices changing.
 
 Sometimes you need to ensure that a subsequent call to :c:func:`xa_store`
 will not need to allocate memory.  The :c:func:`xa_reserve` function
-will store a reserved entry at the indicated index.  Users of the normal
-API will see this entry as containing ``NULL``.  If you do not need to
-use the reserved entry, you can call :c:func:`xa_release` to remove the
-unused entry.  If another user has stored to the entry in the meantime,
-:c:func:`xa_release` will do nothing; if instead you want the entry to
-become ``NULL``, you should use :c:func:`xa_erase`.
+will store a reserved entry at the indicated index.  Users of the
+normal API will see this entry as containing ``NULL``.  If you do
+not need to use the reserved entry, you can call :c:func:`xa_release`
+to remove the unused entry.  If another user has stored to the entry
+in the meantime, :c:func:`xa_release` will do nothing; if instead you
+want the entry to become ``NULL``, you should use :c:func:`xa_erase`.
+Using :c:func:`xa_insert` on a reserved entry will fail.
 
 If all entries in the array are ``NULL``, the :c:func:`xa_empty` function
 will return ``true``.
@@ -183,6 +184,8 @@ Takes xa_lock internally:
  * :c:func:`xa_store_bh`
  * :c:func:`xa_store_irq`
  * :c:func:`xa_insert`
+ * :c:func:`xa_insert_bh`
+ * :c:func:`xa_insert_irq`
  * :c:func:`xa_erase`
  * :c:func:`xa_erase_bh`
  * :c:func:`xa_erase_irq`