[reactos] 01/02: [FREELDR] Add FAT caching to FAT filesystem driver. This significantly increases the reading speed
https://git.reactos.org/?p=reactos.git;a=commitdiff;h=195dc3048464db0ff58954...
commit 195dc3048464db0ff58954d3920d1759230dec3c Author: Victor Perevertkin victor@perevertkin.ru AuthorDate: Tue Jul 9 17:22:28 2019 +0300 Commit: Victor Perevertkin victor@perevertkin.ru CommitDate: Sun Sep 29 13:24:31 2019 +0300
[FREELDR] Add FAT caching to FAT filesystem driver. This significantly increases the reading speed --- boot/freeldr/freeldr/lib/fs/fat.c | 145 +++++++++++++++++++++++++++----------- 1 file changed, 102 insertions(+), 43 deletions(-)
diff --git a/boot/freeldr/freeldr/lib/fs/fat.c b/boot/freeldr/freeldr/lib/fs/fat.c index f16f03a57e1..b973a64dd70 100644 --- a/boot/freeldr/freeldr/lib/fs/fat.c +++ b/boot/freeldr/freeldr/lib/fs/fat.c @@ -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)
-
Victor Perevertkin