Added opt-in lazy sector release to reduce O(N²) deletion (issue #70)

common/CMakeLists.txt

@@ -23,6 +23,7 @@ target_sources(${PROJECT_NAME} PRIVATE
 	${CMAKE_CURRENT_LIST_DIR}/src/lx_nand_flash_format_extended.c
 	${CMAKE_CURRENT_LIST_DIR}/src/lx_nand_flash_free_block_list_add.c
 	${CMAKE_CURRENT_LIST_DIR}/src/lx_nand_flash_initialize.c
+	${CMAKE_CURRENT_LIST_DIR}/src/lx_nand_flash_logical_group_compact.c
 	${CMAKE_CURRENT_LIST_DIR}/src/lx_nand_flash_mapped_block_list_add.c
 	${CMAKE_CURRENT_LIST_DIR}/src/lx_nand_flash_mapped_block_list_get.c
 	${CMAKE_CURRENT_LIST_DIR}/src/lx_nand_flash_mapped_block_list_remove.c

common/inc/lx_api.h

@@ -274,6 +274,17 @@ typedef unsigned long long                      ULONG64;
 #define LX_NAND_FLASH_MAX_METADATA_BLOCKS           4
 #endif
 
+/* When LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE is defined, sector releases from full blocks
+   are deferred when free block count exceeds the threshold below (opt-in, default: off).
+   Requires pages_per_block <= 4095 (bit 12 is reserved for COMPACTION_PENDING flag).  */
+/* #define LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE */
+
+#ifdef LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE
+#ifndef LX_NAND_FLASH_SECTOR_RELEASE_LAZY_THRESHOLD
+#define LX_NAND_FLASH_SECTOR_RELEASE_LAZY_THRESHOLD 10u
+#endif
+#endif
+
 #ifndef LX_UTILITY_SHORT_SET
 #define LX_UTILITY_SHORT_SET(address, value)        *((USHORT*)(address)) = (USHORT)(value)
 #endif
@@ -328,6 +339,11 @@ typedef unsigned long long                      ULONG64;
 #define LX_NAND_BLOCK_STATUS_FULL                   0x4000u
 #define LX_NAND_BLOCK_STATUS_NON_SEQUENTIAL         0x2000u
 #define LX_NAND_BLOCK_STATUS_MAPPING_PRESENT        0x1000u
+#ifdef LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE
+/* Repurpose the otherwise-unused MAPPING_PRESENT bit to signal a block whose compaction
+   has been deferred.  Only valid when pages_per_block <= 4095.  */
+#define LX_NAND_BLOCK_STATUS_COMPACTION_PENDING     LX_NAND_BLOCK_STATUS_MAPPING_PRESENT
+#endif
 #define LX_NAND_BLOCK_STATUS_PAGE_NUMBER_MASK       0x0FFFu
 #define LX_NAND_BLOCK_STATUS_FREE                   0xFFFFu
 #define LX_NAND_BLOCK_STATUS_BAD                    0xFF00u
@@ -402,6 +418,12 @@ typedef struct LX_NAND_FLASH_STRUCT
     USHORT                         *lx_nand_flash_block_list;
     ULONG                           lx_nand_flash_block_list_size;
     ULONG                           lx_nand_flash_free_block_list_tail;
+#ifdef LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE
+    /* Parallel to block_mapping_table: physical block with pending compaction for a group,
+       or LX_NAND_BLOCK_UNMAPPED when no compaction is pending.  */
+    USHORT                         *lx_nand_flash_block_compaction_table;
+    ULONG                           lx_nand_flash_block_compaction_table_size;
+#endif
     ULONG                           lx_nand_flash_mapped_block_list_head;
 
     ULONG                           lx_nand_flash_metadata_block_number;
@@ -771,6 +793,9 @@ UINT    _lx_nand_flash_metadata_write(LX_NAND_FLASH *nand_flash, UCHAR* main_buf
 VOID    _lx_nand_flash_system_error(LX_NAND_FLASH *nand_flash, UINT error_code, ULONG block, ULONG page);
 UINT    _lx_nand_flash_256byte_ecc_check(UCHAR *page_buffer, UCHAR *ecc_buffer);
 UINT    _lx_nand_flash_256byte_ecc_compute(UCHAR *page_buffer, UCHAR *ecc_buffer);
+#ifdef LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE
+UINT    _lx_nand_flash_logical_group_compact(LX_NAND_FLASH *nand_flash, ULONG logical_group);
+#endif
 
 UINT    _lx_nor_flash_block_reclaim(LX_NOR_FLASH *nor_flash);
 UINT    _lx_nor_flash_driver_block_erase(LX_NOR_FLASH *nor_flash, ULONG block, ULONG erase_count);

common/src/lx_nand_flash_block_allocate.c

@@ -9,6 +9,7 @@
  * SPDX-License-Identifier: MIT
  **************************************************************************/
 
+// Some portions generated by Copilot (Sonnet 4.6).
 
 /**************************************************************************/
 /**************************************************************************/
@@ -75,6 +76,43 @@ UINT  _lx_nand_flash_block_allocate(LX_NAND_FLASH* nand_flash, ULONG* block)
     if (nand_flash -> lx_nand_flash_free_block_list_tail == 0)
     {
 
+#ifdef LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE
+        {
+
+        ULONG   lg;
+        UINT    compact_status;
+
+        /* Emergency compaction: find any pending compaction and execute it to
+           reclaim the old full block.  */
+        for (lg = 0; lg < nand_flash -> lx_nand_flash_total_blocks; lg++)
+        {
+
+            if (nand_flash -> lx_nand_flash_block_compaction_table[lg] != (USHORT)LX_NAND_BLOCK_UNMAPPED)
+            {
+
+                compact_status = _lx_nand_flash_logical_group_compact(nand_flash, lg);
+
+                if (compact_status == LX_SUCCESS)
+                {
+
+                    /* Retry the allocation after compaction freed a block.  */
+                    if (nand_flash -> lx_nand_flash_free_block_list_tail > 0)
+                    {
+
+                        nand_flash -> lx_nand_flash_free_block_list_tail--;
+                        *block = nand_flash -> lx_nand_flash_block_list[nand_flash -> lx_nand_flash_free_block_list_tail];
+                        return(LX_SUCCESS);
+                    }
+                }
+
+                /* Attempt only one compaction per allocate call.  */
+                break;
+            }
+        }
+
+        }
+#endif /* LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE */
+
         /* Empty list, return error.  */
         return(LX_NO_BLOCKS);
     }

common/src/lx_nand_flash_block_data_move.c

@@ -9,6 +9,7 @@
  * SPDX-License-Identifier: MIT
  **************************************************************************/
 
+// Some portions generated by Copilot (Sonnet 4.6).
 
 /**************************************************************************/
 /**************************************************************************/
@@ -111,6 +112,33 @@ ULONG       block_mapping_index;
         return(LX_ERROR);
     }
 
+#ifdef LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE
+    /* If this logical group has a pending compaction source, redirect the
+       data move to a full logical-group compact to correctly merge data from
+       both source blocks.  */
+    if (nand_flash -> lx_nand_flash_block_compaction_table[block_mapping_index] != (USHORT)LX_NAND_BLOCK_UNMAPPED)
+    {
+
+        /* Return the pre-allocated new_block to the free list.  */
+        status = _lx_nand_flash_block_status_set(nand_flash, new_block, LX_NAND_BLOCK_STATUS_FREE);
+
+        if (status)
+        {
+            _lx_nand_flash_system_error(nand_flash, status, new_block, 0);
+            return(LX_ERROR);
+        }
+
+        _lx_nand_flash_free_block_list_add(nand_flash, new_block);
+
+        /* Restore block_mapping_index to the mapped list; mapped_block_list_get
+           already removed it before this function was called.  */
+        _lx_nand_flash_mapped_block_list_add(nand_flash, block_mapping_index);
+
+        /* Perform full compaction merge of both source blocks.  */
+        return(_lx_nand_flash_logical_group_compact(nand_flash, block_mapping_index));
+    }
+#endif /* LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE */
+
     /* Set new block status to allocated for now.  */
     new_block_status = LX_NAND_BLOCK_STATUS_ALLOCATED;
 

common/src/lx_nand_flash_defragment.c

@@ -9,6 +9,7 @@
  * SPDX-License-Identifier: MIT
  **************************************************************************/
 
+// Some portions generated by Copilot (Sonnet 4.6).
 
 /**************************************************************************/
 /**************************************************************************/
@@ -72,10 +73,38 @@
 UINT  _lx_nand_flash_defragment(LX_NAND_FLASH *nand_flash)
 {
 
+#ifdef LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE
+
+UINT    status;
+ULONG   lg;
+
+    /* Compact every logical group that has a deferred compaction pending.  */
+    for (lg = 0; lg < nand_flash -> lx_nand_flash_total_blocks; lg++)
+    {
+
+        if (nand_flash -> lx_nand_flash_block_compaction_table[lg] != (USHORT)LX_NAND_BLOCK_UNMAPPED)
+        {
+
+            status = _lx_nand_flash_logical_group_compact(nand_flash, lg);
+
+            /* On error, continue to compact remaining groups.  */
+            if (status)
+            {
+                _lx_nand_flash_system_error(nand_flash, status, lg, 0);
+            }
+        }
+    }
+
+    return(LX_SUCCESS);
+
+#else
+
     LX_PARAMETER_NOT_USED(nand_flash);
 
     /* Return not supported.  */
     return(LX_NOT_SUPPORTED);
+
+#endif /* LX_NAND_FLASH_ENABLE_LAZY_SECTOR_RELEASE */
 }