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[FREELDR] Add FAT caching to FAT filesystem driver.

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This significantly increases the reading speed
This commit is contained in:
Victor Perevertkin 2019-07-09 17:22:28 +03:00
parent be1f95527a
commit 195dc30484
1 changed files with 102 additions and 43 deletions
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145
boot/freeldr/freeldr/lib/fs/fat.c
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@ -39,21 +39,27 @@ BOOLEAN FatReadVolumeSectors(PFAT_VOLUME_INFO Volume, ULONG SectorNumber, ULO
#define TAG_FAT_FILE 'FtaF'
#define TAG_FAT_VOLUME 'VtaF'
#define TAG_FAT_BUFFER 'BtaF'
#define TAG_FAT_CACHE 'HtaF'
#define FAT_MAX_CACHE_SIZE (256 * 1024) // 256 KiB, note: it should fit maximum FAT12 FAT size (6144 bytes)
typedef struct _FAT_VOLUME_INFO
{
ULONG BytesPerSector; /* Number of bytes per sector */
ULONG SectorsPerCluster; /* Number of sectors per cluster */
PUCHAR FatCache; /* A part of 1st FAT cached in memory */
PULONG FatCacheIndex; /* Cached sector's indexes */
ULONG FatCacheSize; /* Size of the cache in sectors */
ULONG FatSectorStart; /* Starting sector of 1st FAT table */
ULONG ActiveFatSectorStart; /* Starting sector of active FAT table */
ULONG NumberOfFats; /* Number of FAT tables */
ULONG SectorsPerFat; /* Sectors per FAT table */
ULONG RootDirSectorStart; /* Starting sector of the root directory (non-fat32) */
ULONG RootDirSectors; /* Number of sectors of the root directory (non-fat32) */
ULONG RootDirStartCluster; /* Starting cluster number of the root directory (fat32 only) */
ULONG DataSectorStart; /* Starting sector of the data area */
ULONG FatType; /* FAT12, FAT16, FAT32, FATX16 or FATX32 */
ULONG DeviceId;
UINT16 BytesPerSector; /* Number of bytes per sector */
UINT8 FatType; /* FAT12, FAT16, FAT32, FATX16 or FATX32 */
UINT8 NumberOfFats; /* Number of FAT tables */
UINT8 SectorsPerCluster; /* Number of sectors per cluster */
} FAT_VOLUME_INFO;
PFAT_VOLUME_INFO FatVolumes[MAX_FDS];
@ -139,7 +145,7 @@ VOID FatSwapFatXDirEntry(PFATX_DIRENTRY Obj)
BOOLEAN FatOpenVolume(PFAT_VOLUME_INFO Volume, PFAT_BOOTSECTOR BootSector, ULONGLONG PartitionSectorCount)
{
char ErrMsg[80];
ULONG FatSize;
ULONG FatSize, i;
PFAT_BOOTSECTOR FatVolumeBootSector;
PFAT32_BOOTSECTOR Fat32VolumeBootSector;
PFATX_BOOTSECTOR FatXVolumeBootSector;
@ -315,6 +321,39 @@ BOOLEAN FatOpenVolume(PFAT_VOLUME_INFO Volume, PFAT_BOOTSECTOR BootSector, ULONG
}
}
Volume->FatCacheSize = min(Volume->SectorsPerFat, FAT_MAX_CACHE_SIZE / Volume->BytesPerSector);
TRACE("FAT cache is %d sectors, %d bytes\n", Volume->FatCacheSize, Volume->FatCacheSize * Volume->BytesPerSector);
Volume->FatCache = FrLdrTempAlloc(Volume->FatCacheSize * Volume->BytesPerSector, TAG_FAT_CACHE);
if (!Volume->FatCache)
{
FileSystemError("Cannot allocate memory for FAT cache");
return FALSE;
}
Volume->FatCacheIndex = FrLdrTempAlloc(Volume->FatCacheSize * sizeof(*Volume->FatCacheIndex), TAG_FAT_VOLUME);
if (!Volume->FatCacheIndex)
{
FileSystemError("Cannot allocate memory for FAT cache index");
FrLdrTempFree(Volume->FatCache, TAG_FAT_CACHE);
return FALSE;
}
// read the beginning of the FAT (or the whole one) to cache
if (!FatReadVolumeSectors(Volume, Volume->ActiveFatSectorStart, Volume->FatCacheSize, Volume->FatCache))
{
FileSystemError("Error when reading FAT cache");
FrLdrTempFree(Volume->FatCache, TAG_FAT_CACHE);
FrLdrTempFree(Volume->FatCacheIndex, TAG_FAT_VOLUME);
return FALSE;
}
// fill the index with sector numbers
for (i = 0; i < Volume->FatCacheSize; i++)
{
Volume->FatCacheIndex[i] = Volume->ActiveFatSectorStart + i;
}
return TRUE;
}
@ -899,54 +938,76 @@ void FatParseShortFileName(PCHAR Buffer, PDIRENTRY DirEntry)
//TRACE("FatParseShortFileName() ShortName = %s\n", Buffer);
}
/**
* @brief Reads 1-4 sectors from FAT using the cache
*/
static
PUCHAR FatGetFatSector(PFAT_VOLUME_INFO Volume, UINT32 FatSectorNumber)
{
UINT32 SectorNumAbsolute = Volume->ActiveFatSectorStart + FatSectorNumber;
UINT32 CacheIndex = FatSectorNumber % Volume->FatCacheSize;
ASSERT(FatSectorNumber < Volume->SectorsPerFat);
// cache miss
if (Volume->FatCacheIndex[CacheIndex] != SectorNumAbsolute)
{
UINT32 SectorsToRead = min(Volume->FatCacheSize - CacheIndex, min(Volume->SectorsPerFat - SectorNumAbsolute, 4));
UINT8 i;
if (!FatReadVolumeSectors(Volume, SectorNumAbsolute, SectorsToRead, &Volume->FatCache[CacheIndex * Volume->BytesPerSector]))
{
return NULL;
}
for (i = 0; i < SectorsToRead; i++)
{
Volume->FatCacheIndex[CacheIndex + i] = SectorNumAbsolute + i;
}
TRACE("FAT cache miss: read sector 0x%x from disk\n", SectorNumAbsolute);
}
else
{
TRACE("FAT cache hit: sector 0x%x present\n", SectorNumAbsolute);
}
return &Volume->FatCache[CacheIndex * Volume->BytesPerSector];
}
/*
* FatGetFatEntry()
* returns the Fat entry for a given cluster number
*/
BOOLEAN FatGetFatEntry(PFAT_VOLUME_INFO Volume, ULONG Cluster, ULONG* ClusterPointer)
{
ULONG fat = 0;
UINT32 FatOffset;
UINT32 ThisFatSecNum;
UINT32 ThisFatEntOffset;
ULONG SectorCount;
UINT32 FatOffset, ThisFatSecNum, ThisFatEntOffset, fat;
PUCHAR ReadBuffer;
BOOLEAN Success = TRUE;
//TRACE("FatGetFatEntry() Retrieving FAT entry for cluster %d.\n", Cluster);
// We need a buffer for 2 sectors
ReadBuffer = FrLdrTempAlloc(2 * Volume->BytesPerSector, TAG_FAT_BUFFER);
if (!ReadBuffer)
{
return FALSE;
}
TRACE("FatGetFatEntry() Retrieving FAT entry for cluster %d.\n", Cluster);
switch(Volume->FatType)
{
case FAT12:
FatOffset = Cluster + (Cluster / 2);
ThisFatSecNum = Volume->ActiveFatSectorStart + (FatOffset / Volume->BytesPerSector);
ThisFatSecNum = FatOffset / Volume->BytesPerSector;
ThisFatEntOffset = (FatOffset % Volume->BytesPerSector);
TRACE("FatOffset: %d\n", FatOffset);
TRACE("ThisFatSecNum: %d\n", ThisFatSecNum);
TRACE("ThisFatEntOffset: %d\n", ThisFatEntOffset);
if (ThisFatEntOffset == (Volume->BytesPerSector - 1))
{
SectorCount = 2;
}
else
{
SectorCount = 1;
}
// The cluster pointer can span within two sectors, but the FatGetFatSector function
// reads 4 sectors most times, except when we are at the edge of FAT cache
// and/or FAT region on the disk. For FAT12 the whole FAT would be cached so
// there will be no situation when the first sector is at the end of the cache
// and the next one is in the beginning
if (!FatReadVolumeSectors(Volume, ThisFatSecNum, SectorCount, ReadBuffer))
ReadBuffer = FatGetFatSector(Volume, ThisFatSecNum);
if (!ReadBuffer)
{
Success = FALSE;
break;
return FALSE;
}
fat = *((USHORT *) (ReadBuffer + ThisFatEntOffset));
@ -962,13 +1023,13 @@ BOOLEAN FatGetFatEntry(PFAT_VOLUME_INFO Volume, ULONG Cluster, ULONG* ClusterPoi
case FATX16:
FatOffset = (Cluster * 2);
ThisFatSecNum = Volume->ActiveFatSectorStart + (FatOffset / Volume->BytesPerSector);
ThisFatSecNum = FatOffset / Volume->BytesPerSector;
ThisFatEntOffset = (FatOffset % Volume->BytesPerSector);
if (!FatReadVolumeSectors(Volume, ThisFatSecNum, 1, ReadBuffer))
ReadBuffer = FatGetFatSector(Volume, ThisFatSecNum);
if (!ReadBuffer)
{
Success = FALSE;
break;
return FALSE;
}
fat = *((USHORT *) (ReadBuffer + ThisFatEntOffset));
@ -980,10 +1041,11 @@ BOOLEAN FatGetFatEntry(PFAT_VOLUME_INFO Volume, ULONG Cluster, ULONG* ClusterPoi
case FATX32:
FatOffset = (Cluster * 4);
ThisFatSecNum = Volume->ActiveFatSectorStart + (FatOffset / Volume->BytesPerSector);
ThisFatSecNum = FatOffset / Volume->BytesPerSector;
ThisFatEntOffset = (FatOffset % Volume->BytesPerSector);
if (!FatReadVolumeSectors(Volume, ThisFatSecNum, 1, ReadBuffer))
ReadBuffer = FatGetFatSector(Volume, ThisFatSecNum);
if (!ReadBuffer)
{
Success = FALSE;
break;
@ -997,17 +1059,14 @@ BOOLEAN FatGetFatEntry(PFAT_VOLUME_INFO Volume, ULONG Cluster, ULONG* ClusterPoi
default:
ERR("Unknown FAT type %d\n", Volume->FatType);
Success = FALSE;
break;
return FALSE;
}
//TRACE("FAT entry is 0x%x.\n", fat);
FrLdrTempFree(ReadBuffer, TAG_FAT_BUFFER);
TRACE("FAT entry is 0x%x.\n", fat);
*ClusterPointer = fat;
return Success;
return TRUE;
}
ULONG FatCountClustersInChain(PFAT_VOLUME_INFO Volume, ULONG StartCluster)