list_cmp_func_t introduced, using const.

v5.12-rc6-9-g4f0f586bf0c8

All list_sort functions use the list_cmp_func_t type, which compares
list_head member types. These are now required to be `const` as the
compiler will now check them. This propagates into our callers.

Signed-off-by: Auke Kok <auke.kok@versity.com>

kmod/src/Makefile.kernelcompat

@@ -267,3 +267,11 @@ endif
 ifneq (,$(shell grep 'typedef __u32 __bitwise blk_opf_t' include/linux/blk_types.h))
 ccflags-y += -DKC_HAVE_BLK_OPF_T=1
 endif
+
+#
+# v5.12-rc6-9-g4f0f586bf0c8
+#
+# list_sort cmp function takes const list_head args
+ifneq (,$(shell grep 'const struct list_head ., const struct list_head .' include/linux/list_sort.h))
+ccflags-y += -DKC_LIST_CMP_CONST_ARG_LIST_HEAD
+endif

kmod/src/inode.c

@@ -979,10 +979,10 @@ static bool inode_has_index(umode_t mode, u8 type)
 	}
 }
 
-static int cmp_index_lock(void *priv, struct list_head *A, struct list_head *B)
+static int cmp_index_lock(void *priv, KC_LIST_CMP_CONST struct list_head *A, KC_LIST_CMP_CONST struct list_head *B)
 {
-	struct index_lock *a = list_entry(A, struct index_lock, head);
-	struct index_lock *b = list_entry(B, struct index_lock, head);
+	KC_LIST_CMP_CONST struct index_lock *a = list_entry(A, KC_LIST_CMP_CONST struct index_lock, head);
+	KC_LIST_CMP_CONST struct index_lock *b = list_entry(B, KC_LIST_CMP_CONST struct index_lock, head);
 
 	return ((int)a->type - (int)b->type) ?:
 	       scoutfs_cmp_u64s(a->major, b->major) ?:

kmod/src/item.c

@@ -2241,18 +2241,18 @@ u64 scoutfs_item_dirty_pages(struct super_block *sb)
 	return (u64)atomic_read(&cinf->dirty_pages);
 }
 
-static int cmp_pg_start(void *priv, struct list_head *A, struct list_head *B)
+static int cmp_pg_start(void *priv, KC_LIST_CMP_CONST struct list_head *A, KC_LIST_CMP_CONST struct list_head *B)
 {
-	struct cached_page *a = list_entry(A, struct cached_page, dirty_head);
-	struct cached_page *b = list_entry(B, struct cached_page, dirty_head);
+	KC_LIST_CMP_CONST struct cached_page *a = list_entry(A, KC_LIST_CMP_CONST struct cached_page, dirty_head);
+	KC_LIST_CMP_CONST struct cached_page *b = list_entry(B, KC_LIST_CMP_CONST struct cached_page, dirty_head);
 
 	return scoutfs_key_compare(&a->start, &b->start);
 }
 
-static int cmp_item_key(void *priv, struct list_head *A, struct list_head *B)
+static int cmp_item_key(void *priv, KC_LIST_CMP_CONST struct list_head *A, KC_LIST_CMP_CONST struct list_head *B)
 {
-	struct cached_item *a = list_entry(A, struct cached_item, dirty_head);
-	struct cached_item *b = list_entry(B, struct cached_item, dirty_head);
+	KC_LIST_CMP_CONST struct cached_item *a = list_entry(A, KC_LIST_CMP_CONST struct cached_item, dirty_head);
+	KC_LIST_CMP_CONST struct cached_item *b = list_entry(B, KC_LIST_CMP_CONST struct cached_item, dirty_head);
 
 	return scoutfs_key_compare(&a->key, &b->key);
 }

kmod/src/kernelcompat.h

@@ -278,4 +278,10 @@ ssize_t kc_generic_file_buffered_write(struct kiocb *iocb, const struct iovec *i
 typedef unsigned int blk_opf_t;
 #endif
 
+#ifdef KC_LIST_CMP_CONST_ARG_LIST_HEAD
+#define KC_LIST_CMP_CONST const
+#else
+#define KC_LIST_CMP_CONST
+#endif
+
 #endif

kmod/src/key.h

@@ -125,8 +125,8 @@ static inline bool scoutfs_key_is_ones(struct scoutfs_key *key)
  * other alternatives across keys that first differ in any of the
  * values.  Say maybe 20% faster than memcmp.
  */
-static inline int scoutfs_key_compare(struct scoutfs_key *a,
-				      struct scoutfs_key *b)
+static inline int scoutfs_key_compare(const struct scoutfs_key *a,
+				      const struct scoutfs_key *b)
 {
 	return scoutfs_cmp(a->sk_zone, b->sk_zone) ?:
 	  scoutfs_cmp(le64_to_cpu(a->_sk_first), le64_to_cpu(b->_sk_first)) ?:
@@ -142,10 +142,10 @@ static inline int scoutfs_key_compare(struct scoutfs_key *a,
  *       1: a_start > b_end
  *  else 0: ranges overlap
  */
-static inline int scoutfs_key_compare_ranges(struct scoutfs_key *a_start,
-				             struct scoutfs_key *a_end,
-				             struct scoutfs_key *b_start,
-				             struct scoutfs_key *b_end)
+static inline int scoutfs_key_compare_ranges(const struct scoutfs_key *a_start,
+				             const struct scoutfs_key *a_end,
+				             const struct scoutfs_key *b_start,
+				             const struct scoutfs_key *b_end)
 {
 	return scoutfs_key_compare(a_end, b_start) < 0 ? -1 :
 	       scoutfs_key_compare(a_start, b_end) > 0 ? 1 :

kmod/src/recov.c

@@ -76,10 +76,10 @@ static struct recov_pending *lookup_pending(struct recov_info *recinf, u64 rid,
  * We keep the pending list sorted by rid so that we can iterate over
  * them.  The list should be small and shouldn't be used often.
  */
-static int cmp_pending_rid(void *priv, struct list_head *A, struct list_head *B)
+static int cmp_pending_rid(void *priv, KC_LIST_CMP_CONST struct list_head *A, KC_LIST_CMP_CONST struct list_head *B)
 {
-	struct recov_pending *a = list_entry(A, struct recov_pending, head);
-	struct recov_pending *b = list_entry(B, struct recov_pending, head);
+	KC_LIST_CMP_CONST struct recov_pending *a = list_entry(A, KC_LIST_CMP_CONST struct recov_pending, head);
+	KC_LIST_CMP_CONST struct recov_pending *b = list_entry(B, KC_LIST_CMP_CONST struct recov_pending, head);
 
 	return scoutfs_cmp_u64s(a->rid, b->rid);
 }