fat32: fix pre-alloc cluster leak; add write-handle ref-count

- Remove FAT_WRITE_PREALLOC_BYTES (redundant at typical cluster sizes)
- Simplify fatPreallocClusterCount to always return MAX_CLUSTERS
- FAT32CloseFile: truncate pre-allocated tail clusters back to ByteSize
  on close, freeing FAT chain entries beyond the file's real size
- Add TFATWriteRef + WriteRefs[32] in TFATVolumeCtx and Registered flag
  on TFATOpenFile to track concurrent write handles per dir entry
- fatRegisterWriteHandle / fatUnregisterWriteHandle: CLI-guarded slot scan
  keyed by (DirLoc.SectorLBA, DirLoc.EntryIdx)
- Register on first FAT chain extension in FAT32EnsureCapacityForWrite
- Truncation in FAT32CloseFile skipped unless this is the last writer
  (prevents RunMap corruption in concurrent-open scenarios)
- Add forward decl for fatFreeClusterChain to fix ordering issue
- app.iotest: update default path to /disk/vol2/IOTEST.BIN

src/app/app.iotest.pas

@@ -34,7 +34,7 @@ const
     TICK_HZ    = 1024;               { timer ISR frequency }
     IO_WAIT_TIMEOUT_TICKS = 10 * TICK_HZ;
     DELETE_TIMEOUT_TICKS = 5 * TICK_HZ;
-    DEFAULT_PATH : pchar = '/disk/vol0/IOTEST.BIN';
+    DEFAULT_PATH : pchar = '/disk/vol2/IOTEST.BIN';
 
 type
     TIOTSyncWaitCtx = record

src/driver/storage/ctl/ahci/driver.storage.ctl.ahci.pas

@@ -69,7 +69,7 @@ function send_read_capacity(device : PAHCI_Device; sectorCount : puint32; blockS
 implementation
 
 const
-    AHCI_ENABLE_NCQ = false;
+    AHCI_ENABLE_NCQ = true;
 
 function min_u32(a : uint32; b : uint32) : uint32;
 begin
@@ -421,15 +421,15 @@ begin
         start_port(device^.port);
 
         { Re-enable port interrupts and bail — device is non-functional. }
-        device^.port^.int_enable := $40000003;
+        device^.port^.int_enable := $4000000B;
         kfree(buffer);
         exit;
     end;
 
     { Re-enable port interrupts now that IDENTIFY polling is done.
-      $40000003 = bit 0 (D2H Register FIS) | bit 1 (PIO Setup FIS) | bit 30 (Task File Error)
+      $4000000B = bit 0 (D2H Register FIS) | bit 1 (PIO Setup FIS) | bit 3 (Set Device Bits / NCQ) | bit 30 (Task File Error)
-      These three bits cover all normal completions and hardware error events. }
+      Bit 3 is required for NCQ completion notifications via SDB FIS. }
-    device^.port^.int_enable := $40000003;
+    device^.port^.int_enable := $4000000B;
 
     b8 := puint16(buffer);
     memcpy(uint32(buffer), uint32(@device^.ata_info[0]), 512);

src/driver/storage/fs/fat32/driver.storage.fs.fat32.pas

@@ -14,7 +14,8 @@ implementation
 
 uses
     io.syslog,
-    driver.storage.fs.fat32.old,
+    core.util,
+    driver.storage.fs.fat32.vol,
     driver.storage.fs.fat32.core,
     driver.storage.fs.fat32.transfer;
 
@@ -23,13 +24,13 @@ var
 
 procedure FAT32ReleaseVolumeState(volume : PStorage_Volume);
 begin
-    FAT32LegacyReleaseVolumeCtx(volume);
     FAT32ReleaseVolumeCtx(volume);
 end;
 
 procedure init;
 begin
     io.syslog.logln('FAT32', 'init: registering FAT32 filesystem');
+    memset(uint32(@filesystem), 0, sizeof(TFilesystem));
     filesystem.sName := 'FAT32';
     filesystem.system_id := $0B;
     filesystem.readDirCallback := @FAT32ReadDirectory;
@@ -52,6 +53,7 @@ begin
     filesystem.readDirAsyncCallback := nil;
     filesystem.formatParamFlags := FS_FORMAT_PARAM_CLUSTER_SIZE;
 
+    FAT32VolInit(@filesystem);
     driver.storage.fs.mgr.register_filesystem(@filesystem);
 end;
 

src/driver/storage/fs/fat32/driver.storage.fs.fat32.types.pas

@@ -67,17 +67,16 @@ type
     end;
 
 const
-    FAT_CACHE_SETS = 512;
+    FAT_CACHE_SETS = 1024;
-    FAT_CACHE_WAYS = 2;
+    FAT_CACHE_WAYS = 4;
     FAT_CACHE_LINES = FAT_CACHE_SETS * FAT_CACHE_WAYS;
     FAT_TRANSFER_POOL_CAPACITY = 64;
     FAT_ALLOC_HINT_SLOTS = 8;
-    FAT_DIR_HINT_SLOTS = 16;
+    FAT_DIR_HINT_SLOTS = 8;
-    FAT_WRITE_PREALLOC_BYTES = 16 * 1024 * 1024;
     FAT_WRITE_PREALLOC_MAX_CLUSTERS = 2048;
     FAT_WRITE_PREALLOC_MIN_CLUSTERS = 64;
-    FAT_MAX_IO_SECTORS = 2048;
+    FAT_MAX_IO_SECTORS = 2048 * 2;    
-
+    FAT_OPEN_HANDLE_SLOTS = 65000;
 type
     TFATCacheLine = record
         SectorIdx : uint32;
@@ -162,6 +161,13 @@ type
         Exists        : boolean;
         FatDirty      : boolean;
         MetaDirty     : boolean;
+        Registered    : boolean;  { true once registered in the volume write-ref table }
+    end;
+
+    TFATWriteRef = record
+        SectorLBA : uint32;
+        EntryIdx  : uint32;
+        Count     : uint32;  { number of write handles with this dir entry open }
     end;
 
     TFATTransferMode = (ftmRead, ftmWrite);
@@ -215,6 +221,7 @@ type
         HintStamp         : uint32;
         AllocHints        : array[0..FAT_ALLOC_HINT_SLOTS - 1] of TFATAllocHint;
         DirHints          : array[0..FAT_DIR_HINT_SLOTS - 1] of TFATDirHint;
+        WriteRefs         : array[0..FAT_OPEN_HANDLE_SLOTS - 1] of TFATWriteRef;
     end;
 
 implementation