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-rw-r--r--include/linux/swapops.h8
1 files changed, 5 insertions, 3 deletions
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 792d16d..47ead51 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -9,13 +9,15 @@
* get good packing density in that tree, so the index should be dense in
* the low-order bits.
*
- * We arrange the `type' and `offset' fields so that `type' is at the five
+ * We arrange the `type' and `offset' fields so that `type' is at the seven
* high-order bits of the swp_entry_t and `offset' is right-aligned in the
- * remaining bits.
+ * remaining bits. Although `type' itself needs only five bits, we allow for
+ * shmem/tmpfs to shift it all up a further two bits: see swp_to_radix_entry().
*
* swp_entry_t's are *never* stored anywhere in their arch-dependent format.
*/
-#define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT)
+#define SWP_TYPE_SHIFT(e) ((sizeof(e.val) * 8) - \
+ (MAX_SWAPFILES_SHIFT + RADIX_TREE_EXCEPTIONAL_SHIFT))
#define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1)
/*