MDEV-38419: Fix some clang-21 -fsanitize=memory failures

fil_space_t::free_page(): Turn a parameter into a template parameter,
and remove some duplicated code. This fixes an error that was flagged
by clang++-21 -fsanitize=memory in buf_page_create().

fseg_create(): Merge the parameter reserved_extent to n_reserved.
This fixes an error about n_reserved being uninitialized.

fseg_alloc_free_page_low(): Simplify a debug assertion.

flst_add_last(), flst_remove(): Reduce the scope of a conditionally
initialized variable.

Reviewed by: Thirunarayanan Balathandayuthapani

storage/innobase/buf/buf0buf.cc

@@ -3474,7 +3474,7 @@ buf_block_t*
 buf_page_create(fil_space_t *space, uint32_t offset,
                 ulint zip_size, mtr_t *mtr, buf_block_t *free_block) noexcept
 {
-  space->free_page(offset, false);
+  space->free_page<false>(offset);
   return buf_page_create_low({space->id, offset}, zip_size, mtr, free_block);
 }
 

storage/innobase/fsp/fsp0fsp.cc

@@ -1683,8 +1683,7 @@ fseg_create(fil_space_t *space, ulint byte_offset, mtr_t *mtr, dberr_t *err,
 {
 	fseg_inode_t*	inode;
 	ib_id_t		seg_id;
-	uint32_t	n_reserved;
-	bool		reserved_extent = false;
+	uint32_t	n_reserved = 0;
 
 	DBUG_ENTER("fseg_create");
 
@@ -1712,16 +1711,16 @@ inode_alloc:
 	if (!inode) {
 		block = nullptr;
 reserve_extent:
-		if (!has_done_reservation && !reserved_extent) {
+		if (!has_done_reservation && !n_reserved) {
 			*err = fsp_reserve_free_extents(&n_reserved, space, 2,
 							FSP_NORMAL, mtr);
 			if (UNIV_UNLIKELY(*err != DB_SUCCESS)) {
 				DBUG_RETURN(nullptr);
 			}
 
+			ut_ad(n_reserved > 0);
 			/* Extents reserved successfully. So
 			try allocating the page or inode */
-			reserved_extent = true;
 			if (inode) {
 				goto page_alloc;
 			}
@@ -1791,7 +1790,8 @@ page_alloc:
 				       + block->page.frame, space->id);
 
 funct_exit:
-	if (!has_done_reservation && reserved_extent) {
+	if (n_reserved) {
+		ut_ad(!has_done_reservation);
 		space->release_free_extents(n_reserved);
 	}
 
@@ -2173,8 +2173,6 @@ take_hinted_page:
 		buf_block_t* block = fsp_alloc_free_page(
 			space, hint, mtr, init_mtr, err);
 
-		ut_ad(block || !has_done_reservation || *err);
-
 		if (block) {
 			/* Put the page in the fragment page array of the
 			segment */
@@ -2187,6 +2185,8 @@ take_hinted_page:
 			fseg_set_nth_frag_page_no(
 				seg_inode, iblock, n,
 				block->page.id().page_no(), mtr);
+		} else {
+			ut_ad(*err != DB_SUCCESS);
 		}
 
 		/* fsp_alloc_free_page() invoked fsp_init_file_page()

storage/innobase/fut/fut0lst.cc

@@ -281,12 +281,15 @@ dberr_t flst_add_last(buf_block_t *base, uint16_t boffset,
       return DB_CORRUPTION;
 
     buf_block_t *cur= add;
-    dberr_t err;
-    if (addr.page != add->page.id().page_no() &&
-        !(cur= buf_page_get_gen(page_id_t{add->page.id().space(), addr.page},
-                                add->zip_size(), RW_SX_LATCH, nullptr,
-                                BUF_GET_POSSIBLY_FREED, mtr, &err)))
-      return err;
+    if (addr.page != add->page.id().page_no())
+    {
+      dberr_t err;
+      cur= buf_page_get_gen(page_id_t{add->page.id().space(), addr.page},
+                            add->zip_size(), RW_SX_LATCH, nullptr,
+                            BUF_GET_POSSIBLY_FREED, mtr, &err);
+      if (!cur)
+        return err;
+    }
     return flst_insert_after(base, boffset, cur, addr.boffset,
                              add, aoffset, limit, mtr);
   }
@@ -382,16 +385,21 @@ dberr_t flst_remove(buf_block_t *base, uint16_t boffset,
                     prev_addr.page, prev_addr.boffset, mtr);
   else
   {
-    dberr_t err2;
-    if (next_addr.page == cur->page.id().page_no() ||
-        (cur= buf_page_get_gen(page_id_t(cur->page.id().space(),
-                                         next_addr.page),
-                               cur->zip_size(), RW_SX_LATCH, nullptr,
-                               BUF_GET_POSSIBLY_FREED, mtr, &err2)))
+    if (next_addr.page == cur->page.id().page_no())
+    write_addr:
       flst_write_addr(*cur, cur->page.frame + next_addr.boffset + FLST_PREV,
                       prev_addr.page, prev_addr.boffset, mtr);
-    else if (err == DB_SUCCESS)
-      err= err2;
+    else
+    {
+      dberr_t err2;
+      cur= buf_page_get_gen(page_id_t(cur->page.id().space(), next_addr.page),
+                            cur->zip_size(), RW_SX_LATCH, nullptr,
+                            BUF_GET_POSSIBLY_FREED, mtr, &err2);
+      if (cur)
+        goto write_addr;
+      if (err == DB_SUCCESS)
+        err= err2;
+    }
   }
 
   byte *len= &base->page.frame[boffset + FLST_LEN];

storage/innobase/include/fil0fil.h

@@ -995,19 +995,16 @@ public:
   @retval nullptr if the tablespace is missing or inaccessible */
   static fil_space_t *get_for_write(ulint id) noexcept;
 
-  /** Add/remove the free page in the freed ranges list.
-  @param[in] offset     page number to be added
-  @param[in] free       true if page to be freed */
-  void free_page(uint32_t offset, bool add=true)
+  /** Add/remove a page in freed_ranges.
+  @tparam add   true=add, false=remove
+  @param offset page number */
+  template<bool add=true> void free_page(uint32_t offset) noexcept
   {
     std::lock_guard<std::mutex> freed_lock(freed_range_mutex);
     if (add)
-      return freed_ranges.add_value(offset);
-
-    if (freed_ranges.empty())
-      return;
-
-    return freed_ranges.remove_value(offset);
+      freed_ranges.add_value(offset);
+    else
+      freed_ranges.remove_value(offset);
   }
 
   /** Add the range of freed pages */

storage/innobase/log/log0recv.cc

@@ -2358,8 +2358,10 @@ static void store_freed_or_init_rec(page_id_t page_id, bool freed)
       space= fil_system.sys_space;
     else
       space= fil_space_get(space_id);
-
-    space->free_page(page_no, freed);
+    if (freed)
+      space->free_page<true>(page_no);
+    else
+      space->free_page<false>(page_no);
     return;
   }