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block-vpc: Write support (Kevin Wolf) 

Add write support for VHD images.

Signed-off-by: Kevin Wolf <kwolf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6458 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
aliguori 2009-01-26 20:27:02 +00:00
parent b71d1c2e11
commit 15d35bc557
1 changed files with 150 additions and 16 deletions
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166
block-vpc.c
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@ -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,
};