diff options
Diffstat (limited to 'block-vpc.c')
| -rw-r--r-- | block-vpc.c | 166 |
1 files changed, 150 insertions, 16 deletions
diff --git a/block-vpc.c b/block-vpc.c index 6d9831540f..24ed6c76d2 100644 --- a/block-vpc.c +++ b/block-vpc.c @@ -2,6 +2,7 @@ * Block driver for Conectix/Microsoft Virtual PC images * * Copyright (c) 2005 Alex Beregszaszi + * Copyright (c) 2009 Kevin Wolf <kwolf@suse.de> * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal @@ -107,10 +108,16 @@ struct vhd_dyndisk_header { typedef struct BDRVVPCState { BlockDriverState *hd; + uint8_t footer_buf[HEADER_SIZE]; + uint64_t free_data_block_offset; int max_table_entries; uint32_t *pagetable; + uint64_t bat_offset; + uint64_t last_bitmap_offset; uint32_t block_size; + uint32_t bitmap_size; + #ifdef CACHE uint8_t *pageentry_u8; uint32_t *pageentry_u32; @@ -135,16 +142,14 @@ static int vpc_open(BlockDriverState *bs, const char *filename, int flags) struct vhd_dyndisk_header* dyndisk_header; uint8_t buf[HEADER_SIZE]; - bs->read_only = 1; // no write support yet - ret = bdrv_file_open(&s->hd, filename, flags); if (ret < 0) return ret; - if (bdrv_pread(s->hd, 0, buf, HEADER_SIZE) != HEADER_SIZE) + if (bdrv_pread(s->hd, 0, s->footer_buf, HEADER_SIZE) != HEADER_SIZE) goto fail; - footer = (struct vhd_footer*) buf; + footer = (struct vhd_footer*) s->footer_buf; if (strncmp(footer->creator, "conectix", 8)) goto fail; @@ -158,26 +163,41 @@ static int vpc_open(BlockDriverState *bs, const char *filename, int flags) != HEADER_SIZE) goto fail; - footer = NULL; dyndisk_header = (struct vhd_dyndisk_header*) buf; if (strncmp(dyndisk_header->magic, "cxsparse", 8)) goto fail; + s->block_size = be32_to_cpu(dyndisk_header->block_size); + s->bitmap_size = ((s->block_size / (8 * 512)) + 511) & ~511; + s->max_table_entries = be32_to_cpu(dyndisk_header->max_table_entries); s->pagetable = qemu_malloc(s->max_table_entries * 4); if (!s->pagetable) goto fail; - if (bdrv_pread(s->hd, be64_to_cpu(dyndisk_header->table_offset), - s->pagetable, s->max_table_entries * 4) != s->max_table_entries * 4) + s->bat_offset = be64_to_cpu(dyndisk_header->table_offset); + if (bdrv_pread(s->hd, s->bat_offset, s->pagetable, + s->max_table_entries * 4) != s->max_table_entries * 4) goto fail; - for (i = 0; i < s->max_table_entries; i++) - be32_to_cpus(&s->pagetable[i]); + s->free_data_block_offset = + (s->bat_offset + (s->max_table_entries * 4) + 511) & ~511; + + for (i = 0; i < s->max_table_entries; i++) { + be32_to_cpus(&s->pagetable[i]); + if (s->pagetable[i] != 0xFFFFFFFF) { + int64_t next = (512 * (int64_t) s->pagetable[i]) + + s->bitmap_size + s->block_size; + + if (next> s->free_data_block_offset) + s->free_data_block_offset = next; + } + } + + s->last_bitmap_offset = (int64_t) -1; - s->block_size = be32_to_cpu(dyndisk_header->block_size); #ifdef CACHE s->pageentry_u8 = qemu_malloc(512); if (!s->pageentry_u8) @@ -196,8 +216,12 @@ static int vpc_open(BlockDriverState *bs, const char *filename, int flags) /* * Returns the absolute byte offset of the given sector in the image file. * If the sector is not allocated, -1 is returned instead. + * + * The parameter write must be 1 if the offset will be used for a write + * operation (the block bitmaps is updated then), 0 otherwise. */ -static inline int64_t get_sector_offset(BlockDriverState *bs, int64_t sector_num) +static inline int64_t get_sector_offset(BlockDriverState *bs, + int64_t sector_num, int write) { BDRVVPCState *s = bs->opaque; uint64_t offset = sector_num * 512; @@ -207,11 +231,24 @@ static inline int64_t get_sector_offset(BlockDriverState *bs, int64_t sector_num pagetable_index = offset / s->block_size; pageentry_index = (offset % s->block_size) / 512; - if (pagetable_index > s->max_table_entries || s->pagetable[pagetable_index] == 0xffffffff) - return -1; // not allocated + if (pagetable_index >= s->max_table_entries || s->pagetable[pagetable_index] == 0xffffffff) + return -1; // not allocated bitmap_offset = 512 * s->pagetable[pagetable_index]; - block_offset = bitmap_offset + 512 + (512 * pageentry_index); + block_offset = bitmap_offset + s->bitmap_size + (512 * pageentry_index); + + // We must ensure that we don't write to any sectors which are marked as + // unused in the bitmap. We get away with setting all bits in the block + // bitmap each time we write to a new block. This might cause Virtual PC to + // miss sparse read optimization, but it's not a problem in terms of + // correctness. + if (write && (s->last_bitmap_offset != bitmap_offset)) { + uint8_t bitmap[s->bitmap_size]; + + s->last_bitmap_offset = bitmap_offset; + memset(bitmap, 0xff, s->bitmap_size); + bdrv_pwrite(s->hd, bitmap_offset, bitmap, s->bitmap_size); + } // printf("sector: %" PRIx64 ", index: %x, offset: %x, bioff: %" PRIx64 ", bloff: %" PRIx64 "\n", // sector_num, pagetable_index, pageentry_index, @@ -248,6 +285,75 @@ static inline int64_t get_sector_offset(BlockDriverState *bs, int64_t sector_num return block_offset; } +/* + * Writes the footer to the end of the image file. This is needed when the + * file grows as it overwrites the old footer + * + * Returns 0 on success and < 0 on error + */ +static int rewrite_footer(BlockDriverState* bs) +{ + int ret; + BDRVVPCState *s = bs->opaque; + int64_t offset = s->free_data_block_offset; + + ret = bdrv_pwrite(s->hd, offset, s->footer_buf, HEADER_SIZE); + if (ret < 0) + return ret; + + return 0; +} + +/* + * Allocates a new block. This involves writing a new footer and updating + * the Block Allocation Table to use the space at the old end of the image + * file (overwriting the old footer) + * + * Returns the sectors' offset in the image file on success and < 0 on error + */ +static int64_t alloc_block(BlockDriverState* bs, int64_t sector_num) +{ + BDRVVPCState *s = bs->opaque; + int64_t bat_offset; + uint32_t index, bat_value; + int ret; + uint8_t bitmap[s->bitmap_size]; + + // Check if sector_num is valid + if ((sector_num < 0) || (sector_num > bs->total_sectors)) + return -1; + + // Write entry into in-memory BAT + index = (sector_num * 512) / s->block_size; + if (s->pagetable[index] != 0xFFFFFFFF) + return -1; + + s->pagetable[index] = s->free_data_block_offset / 512; + + // Initialize the block's bitmap + memset(bitmap, 0xff, s->bitmap_size); + bdrv_pwrite(s->hd, s->free_data_block_offset, bitmap, s->bitmap_size); + + // Write new footer (the old one will be overwritten) + s->free_data_block_offset += s->block_size + s->bitmap_size; + ret = rewrite_footer(bs); + if (ret < 0) + goto fail; + + // Write BAT entry to disk + bat_offset = s->bat_offset + (4 * index); + bat_value = be32_to_cpu(s->pagetable[index]); + ret = bdrv_pwrite(s->hd, bat_offset, &bat_value, 4); + if (ret < 0) + goto fail; + + return get_sector_offset(bs, sector_num, 0); + +fail: + s->free_data_block_offset -= (s->block_size + s->bitmap_size); + return -1; +} + static int vpc_read(BlockDriverState *bs, int64_t sector_num, uint8_t *buf, int nb_sectors) { @@ -256,7 +362,7 @@ static int vpc_read(BlockDriverState *bs, int64_t sector_num, int64_t offset; while (nb_sectors > 0) { - offset = get_sector_offset(bs, sector_num); + offset = get_sector_offset(bs, sector_num, 0); if (offset == -1) { memset(buf, 0, 512); @@ -273,6 +379,34 @@ static int vpc_read(BlockDriverState *bs, int64_t sector_num, return 0; } +static int vpc_write(BlockDriverState *bs, int64_t sector_num, + const uint8_t *buf, int nb_sectors) +{ + BDRVVPCState *s = bs->opaque; + int64_t offset; + int ret; + + while (nb_sectors > 0) { + offset = get_sector_offset(bs, sector_num, 1); + + if (offset == -1) { + offset = alloc_block(bs, sector_num); + if (offset < 0) + return -1; + } + + ret = bdrv_pwrite(s->hd, offset, buf, 512); + if (ret != 512) + return -1; + + nb_sectors--; + sector_num++; + buf += 512; + } + + return 0; +} + static void vpc_close(BlockDriverState *bs) { BDRVVPCState *s = bs->opaque; @@ -289,6 +423,6 @@ BlockDriver bdrv_vpc = { vpc_probe, vpc_open, vpc_read, - NULL, + vpc_write, vpc_close, }; |