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mkfs.fat: Fill in the last known free cluster count hint

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This allows generated FAT32 file systems to pass fsck.fat without
tripping any warnings.
This commit is contained in:
implicitfield 2024-02-26 17:30:21 +04:00 committed by Andrew Kaster
parent e91f60e0f5
commit 012f2fd712
Notes: sideshowbarker 2024-07-17 11:34:34 +09:00 
Author: https://github.com/implicitfield
Commit: https://github.com/SerenityOS/serenity/commit/012f2fd712
Pull-request: https://github.com/SerenityOS/serenity/pull/23356
Reviewed-by: https://github.com/ADKaster ✅
1 changed files with 7 additions and 3 deletions
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10
Userland/Utilities/mkfs.fat.cpp
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@ -470,13 +470,17 @@ static Kernel::DOS7BIOSParameterBlock generate_dos_7_bios_parameter_block(Kernel
return boot_record_fat32;
}
static Kernel::FAT32FSInfo generate_fat32_fs_info(Kernel::DOS7BIOSParameterBlock const& boot_record_fat32)
static Kernel::FAT32FSInfo generate_fat32_fs_info(Kernel::DOS3BIOSParameterBlock const& boot_record, Kernel::DOS7BIOSParameterBlock const& boot_record_fat32)
{
Kernel::FAT32FSInfo fs_info {};
fs_info.lead_signature = 0x41615252;
__builtin_memset(&fs_info.unused1[0], 0, 480);
fs_info.struct_signature = 0x61417272;
fs_info.last_known_free_cluster_count = 0xFFFFFFFF; // Signify that the amount of free clusters is unknown.
{
off_t const fat_sectors = boot_record_fat32.sectors_per_fat_32bit * boot_record.fat_count;
off_t const data_sector_count = boot_record.sector_count_32bit - boot_record.reserved_sector_count - fat_sectors;
fs_info.last_known_free_cluster_count = data_sector_count / boot_record.sectors_per_cluster - 1;
}
fs_info.next_free_cluster_hint = boot_record_fat32.root_directory_cluster + 1;
__builtin_memset(&fs_info.unused2[0], 0, 12);
fs_info.trailing_signature = 0xAA550000;
@ -525,7 +529,7 @@ static ErrorOr<void> format_fat32(Core::File& file, u64 file_size, u32 volume_id
{
auto boot_record = TRY(generate_dos_3_bios_parameter_block(file_size, FATType::FAT32));
auto boot_record_fat32 = generate_dos_7_bios_parameter_block(boot_record, volume_id);
auto fs_info = generate_fat32_fs_info(boot_record_fat32);
auto fs_info = generate_fat32_fs_info(boot_record, boot_record_fat32);
s_bootcode[s_message_offset_offset] = 0x77;
TRY(wipe_file(file, file_size));