forked from KolibriOS/kolibrios
223 lines
6.3 KiB
NASM
223 lines
6.3 KiB
NASM
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; ;;
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;; Contains common resource allocation + freeing code. ;;
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;; ;;
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;; Copyright (C) KolibriOS team 2004-2013. All rights reserved. ;;
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;; Distributed under the terms of the new BSD license. ;;
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;; ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;---------------------------------------------------------------------
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; Frees a resource (block/inode).
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; Input: eax = resource ID.
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; edi = function pointer of ext2_bg_*_bitmap form, to
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; get bitmap of resource.
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; ecx = 0, block; 1, inode.
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; ebp = pointer to EXTFS.
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; Output: Block marked as free in block group.
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; eax = error code.
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;---------------------------------------------------------------------
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ext2_resource_free:
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push ebx edx esi
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; Get block group.
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sub eax, [ebp + EXTFS.superblock + EXT2_SB_STRUC.first_data_block]
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xor edx, edx
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div [ebp + EXTFS.superblock + EXT2_SB_STRUC.blocks_per_group]
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push eax edx
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call edi
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test eax, eax
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jz .fail
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mov esi, eax
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; Read the bitmap.
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mov eax, ebx
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mov edx, eax
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mov ebx, [ebp + EXTFS.ext2_save_block]
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call ext2_block_read
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test eax, eax
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jnz .fail
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pop eax
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; Mark bit free.
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call bitmap_clear_bit
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test eax, eax
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jz @F
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; No need to save anything.
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xor eax, eax
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add esp, 4
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jmp .return
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@@:
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mov eax, edx
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mov ebx, [ebp + EXTFS.ext2_save_block]
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call ext2_block_write
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test eax, eax
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jnz .fail
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; Read the descriptor.
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mov eax, [esp]
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call ext2_bg_read_desc
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test eax, eax
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jz .fail_bg_desc_read
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lea eax, [eax + EXT2_BLOCK_GROUP_DESC.free_blocks_count]
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shl ecx, 1
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add eax, ecx
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inc word[eax]
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lea eax, [ebp + EXTFS.superblock + EXT2_SB_STRUC.free_block_count]
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shl ecx, 1
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add eax, ecx
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inc dword[eax]
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pop eax
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call ext2_bg_write_desc
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.return:
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pop esi edx ebx
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ret
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.fail:
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add esp, 4
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.fail_bg_desc_read:
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add esp, 4
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xor eax, eax
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not eax
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jmp .return
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;---------------------------------------------------------------------
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; Allocates a resource.
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; Input: eax = inode ID for "preference".
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; ebp = pointer to EXTFS.
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; [esp + 4], func pointer to ext2_bg_*_bitmap
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; [esp + 8], pointer to free_*_count in SB.
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; [esp + 12], *_per_group
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; [esp + 16], offset to free_*_count in bg descriptor.
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; [esp + 20], *_count
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; Output: Resource marked as set in block group.
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; eax = error code.
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; ebx = resource ID.
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;---------------------------------------------------------------------
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ext2_resource_alloc:
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; Block allocation is a pretty serious area, since bad allocation
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; can lead to defragmentation. Thus, the best way to allocate that
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; comes to mind is to allocate around an inode as much as possible.
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; On the other hand, this isn't about a single inode/file/directory,
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; and focusing just around the preferred inode would lead to
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; congestion. Thus, after much though, the chosen allocation algorithm
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; is to search forward, then backward.
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push ecx edx esi edi
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cmp dword[esp + 16 + 8], 0
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jnz @F
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; No free blocks.
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xor eax, eax
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not eax
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pop edi esi edx ecx
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ret 20
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@@:
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; Calculate which block group the preferred inode belongs to.
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dec eax
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xor edx, edx
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; EAX = block group.
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div [ebp + EXTFS.superblock + EXT2_SB_STRUC.inodes_per_group]
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push eax
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push eax
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mov edi, .forward
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.test_block_group:
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call dword[esp + 16 + 8 + 4]
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test eax, eax
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jz .fail
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mov esi, eax
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mov eax, ebx
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mov edx, eax
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mov ebx, [ebp + EXTFS.ext2_save_block]
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call ext2_block_read
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test eax, eax
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jnz .fail
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mov ecx, [esp + 16 + 8 + 12]
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call ext2_find_free_bit
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cmp eax, 0xFFFFFFFF
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jne @F
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mov eax, edi
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jmp eax
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@@:
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mov ecx, eax
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mov eax, edx
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mov ebx, [ebp + EXTFS.ext2_save_block]
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call ext2_block_write
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test eax, eax
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jnz .fail
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; ecx: the index of the matched entry.
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; [esp]: block group where we found.
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; [esp + 4]: starting block group.
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; esi: block group descriptor.
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mov eax, [esp] ; Index of block group in which we found.
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mul dword[esp + 16 + 8 + 12]
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add eax, ecx
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mov ebx, eax
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mov eax, [esp + 16 + 8 + 8]
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dec dword[eax]
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mov eax, esi
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add eax, [esp + 16 + 8 + 16]
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dec word[eax]
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pop eax
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call ext2_bg_write_desc
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add esp, 4
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jmp .return
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; Continue forward.
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.forward:
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inc dword[esp]
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mov eax, [esp]
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mul dword[esp + 16 + 8 + 12]
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cmp eax, [esp + 16 + 8 + 20]
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jbe @F
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; We need to go backward.
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mov eax, [esp + 4]
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mov [esp], eax
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mov edi, .backward
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jmp .backward
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@@:
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mov eax, [esp]
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jmp .test_block_group
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; Continue backward.
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.backward:
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cmp dword[esp], 0
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je .fail
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dec dword[esp]
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mov eax, [esp]
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jmp .test_block_group
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.return:
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pop edi esi edx ecx
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ret 20
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.fail:
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add esp, 8
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xor eax, eax
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not eax
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jmp .return |