Re: [Qemu-devel] [PATCH] Bochs Redolog disk image support

[Fabrice Bellard <fabrice@bellard.org>]

Hi,

Supporting Bochs disk images is interesting. I can commit your patch if 
you suppress the unneeded mmap() usage.

Fabrice.

Alex Beregszaszi wrote:
> Hi,
> 
> Looks like I forgot to attach...
> 
> attached is a patch and file adding read-only support for bochs
> "growing" type of disk images.
> 
> I wrote this for converting my bochs images into cow and I'm not
> currently interested in adding write support.
> 
> Also note that altought the bochs "redolog" disk format has more
> subtypes, the growing one is the widely used one. Also there's a
> different format called "sparse", which is not supported by this driver.
> The "flat" format used by bochs is just raw.
> 
> Also it could be speed up by several factors.
> 
> 
> 
> ------------------------------------------------------------------------
> 
> /*
>  * Block driver for the various disk image formats used by Bochs
>  * Currently only for "growing" type in read-only mode
>  * 
>  * Copyright (c) 2005 Alex Beregszaszi
>  * 
>  * Permission is hereby granted, free of charge, to any person obtaining a copy
>  * of this software and associated documentation files (the "Software"), to deal
>  * in the Software without restriction, including without limitation the rights
>  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
>  * copies of the Software, and to permit persons to whom the Software is
>  * furnished to do so, subject to the following conditions:
>  *
>  * The above copyright notice and this permission notice shall be included in
>  * all copies or substantial portions of the Software.
>  *
>  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
>  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
>  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
>  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
>  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
>  * THE SOFTWARE.
>  */
> #ifndef _WIN32
> #include "vl.h"
> #include "block_int.h"
> #include <sys/mman.h>
> 
> /**************************************************************/
> 
> #define HEADER_MAGIC "Bochs Virtual HD Image"
> #define HEADER_VERSION 0x00010000
> #define HEADER_SIZE 512
> 
> #define REDOLOG_TYPE "Redolog"
> #define GROWING_TYPE "Growing"
> 
> // not allocated: 0xffffffff
> 
> // always little-endian
> struct bochs_header {
>     char magic[32]; // "Bochs Virtual HD Image"
>     char type[16]; // "Redolog"
>     char subtype[16]; // "Undoable" / "Volatile" / "Growing"
>     uint32_t version;
>     uint32_t header; // size of header
>     
>     union {
> 	struct {
> 	    uint32_t catalog; // num of entries
> 	    uint32_t bitmap; // bitmap size
> 	    uint32_t extent; // extent size
> 	    uint64_t disk; // disk size
> 	    char padding[HEADER_SIZE - 64 - 8 - 20];
> 	} redolog;
> 	char padding[HEADER_SIZE - 64 - 8];
>     } extra;
> };
> 
> typedef struct BDRVBochsState {
>     int fd;
>     uint32_t *catalog_bitmap;
>     int catalog_size;
>     int catalog_addr;
>     
>     int bitmap_blocks, extent_blocks, extent_size;
> } BDRVBochsState;
> 
> static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
> {
>     const struct bochs_header *bochs = (const void *)buf;
>     
>     if (buf_size < HEADER_SIZE)
> 	return 0;
> 
>     if (!strcmp(bochs->magic, HEADER_MAGIC) &&
> 	!strcmp(bochs->type, REDOLOG_TYPE) &&
> 	!strcmp(bochs->subtype, GROWING_TYPE) &&
> 	(le32_to_cpu(bochs->version) == HEADER_VERSION))
> 	return 100;
> 
>     return 0;
> }
> 
> static int bochs_open(BlockDriverState *bs, const char *filename)
> {
>     BDRVBochsState *s = bs->opaque;
>     int fd;
>     struct bochs_header bochs;
>     int64_t size;
> 
>     fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
>     if (fd < 0) {
>         fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
>         if (fd < 0)
>             return -1;
>     }
>     
>     bs->read_only = 1; // no write support yet
>     
>     s->fd = fd;
> 
>     if (read(fd, &bochs, sizeof(bochs)) != sizeof(bochs)) {
>         goto fail;
>     }
> 
>     if (strcmp(bochs.magic, HEADER_MAGIC) ||
>         strcmp(bochs.type, REDOLOG_TYPE) ||
>         strcmp(bochs.subtype, GROWING_TYPE) ||
> 	(le32_to_cpu(bochs.version) != HEADER_VERSION)) {
>         goto fail;
>     }
> 
>     size = le64_to_cpu(bochs.extra.redolog.disk);
> 
>     bs->total_sectors = size / 512;
>     
>     s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog) * 4 + le32_to_cpu(bochs.header);
>     s->catalog_addr = mmap(get_mmap_addr(s->catalog_size), 
>                               s->catalog_size, 
>                               PROT_READ,
>                               MAP_SHARED, s->fd, 0);
>     if (s->catalog_addr == MAP_FAILED)
>         goto fail;
>     s->catalog_bitmap = s->catalog_addr + le32_to_cpu(bochs.header);
> 
>     s->bitmap_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.bitmap) - 1) / 512;
>     s->extent_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.extent) - 1) / 512;
>     
>     s->extent_size = le32_to_cpu(bochs.extra.redolog.extent);
> 
>     return 0;
>  fail:
>     close(fd);
>     return -1;
> }
> 
> static inline int seek_to_sector(BlockDriverState *bs, int64_t sector_num)
> {
>     BDRVBochsState *s = bs->opaque;
>     int64_t offset = sector_num * 512;
>     int64_t extent_index, extent_offset, bitmap_offset, block_offset;
>     char bitmap_entry;
> 
>     // seek to sector
>     extent_index = offset / s->extent_size;
>     extent_offset = (offset % s->extent_size) / 512;
>     
>     if (le32_to_cpu(s->catalog_bitmap[extent_index]) == 0xffffffff)
>     {
> //	fprintf(stderr, "page not allocated [%x - %x:%x]\n",
> //	    sector_num, extent_index, extent_offset);
> 	return -1; // not allocated
>     }
> 
>     bitmap_offset = s->catalog_size + (512 * le32_to_cpu(s->catalog_bitmap[extent_index]) *
> 	(s->extent_blocks + s->bitmap_blocks));
>     block_offset = bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
>     
> //    fprintf(stderr, "sect: %x [ext i: %x o: %x] -> %x bitmap: %x block: %x\n",
> //	sector_num, extent_index, extent_offset,
> //	le32_to_cpu(s->catalog_bitmap[extent_index]),
> //	bitmap_offset, block_offset);
>     
>     // read in bitmap for current extent
>     lseek(s->fd, bitmap_offset + (extent_offset / 8), SEEK_SET);
>     
>     read(s->fd, &bitmap_entry, 1);
>     
>     if (!((bitmap_entry >> (extent_offset % 8)) & 1))
>     {
> //	fprintf(stderr, "sector (%x) in bitmap not allocated\n",
> //	    sector_num);
> 	return -1; // not allocated
>     }
> 
>     lseek(s->fd, block_offset, SEEK_SET);
>     
>     return 0;
> }
> 
> static int bochs_read(BlockDriverState *bs, int64_t sector_num, 
>                     uint8_t *buf, int nb_sectors)
> {
>     BDRVBochsState *s = bs->opaque;
>     int ret, n;
> 
>     while (nb_sectors > 0) {
> 	if (!seek_to_sector(bs, sector_num))
> 	{
> 	    ret = read(s->fd, buf, 512);
> 	    if (ret != 512)
> 		return -1;
> 	}
> 	else
>             memset(buf, 0, 512);
>         nb_sectors--;
>         sector_num++;
>         buf += 512;
>     }
>     return 0;
> }
> 
> static void bochs_close(BlockDriverState *bs)
> {
>     BDRVBochsState *s = bs->opaque;
>     munmap(s->catalog_addr, s->catalog_size);
>     close(s->fd);
> }
> 
> BlockDriver bdrv_bochs = {
>     "bochs",
>     sizeof(BDRVBochsState),
>     bochs_probe,
>     bochs_open,
>     bochs_read,
>     NULL,
>     bochs_close,
> };
> #endif
> 
> 
> ------------------------------------------------------------------------
> 
> ? block-bochs.c
> ? block-bochs.diff
> Index: Makefile
> ===================================================================
> RCS file: /cvsroot/qemu/qemu/Makefile,v
> retrieving revision 1.82
> diff -u -r1.82 Makefile
> --- Makefile	10 Feb 2005 21:48:51 -0000	1.82
> +++ Makefile	17 Mar 2005 17:27:00 -0000
> @@ -21,7 +21,7 @@
>  	$(MAKE) -C kqemu
>  endif
>  
> -qemu-img$(EXESUF): qemu-img.c block.c block-cow.c block-qcow.c aes.c block-vmdk.c block-cloop.c block-dmg.c
> +qemu-img$(EXESUF): qemu-img.c block.c block-cow.c block-qcow.c aes.c block-vmdk.c block-cloop.c block-dmg.c block-bochs.c
>  	$(CC) -DQEMU_TOOL $(CFLAGS) $(LDFLAGS) $(DEFINES) -o $@ $^ -lz $(LIBS)
>  
>  dyngen$(EXESUF): dyngen.c
> Index: Makefile.target
> ===================================================================
> RCS file: /cvsroot/qemu/qemu/Makefile.target,v
> retrieving revision 1.62
> diff -u -r1.62 Makefile.target
> --- Makefile.target	13 Mar 2005 16:52:10 -0000	1.62
> +++ Makefile.target	17 Mar 2005 17:27:00 -0000
> @@ -309,7 +309,7 @@
>  
>  # must use static linking to avoid leaving stuff in virtual address space
>  VL_OBJS=vl.o osdep.o block.o readline.o monitor.o pci.o console.o 
> -VL_OBJS+=block-cow.o block-qcow.o aes.o block-vmdk.o block-cloop.o block-dmg.o
> +VL_OBJS+=block-cow.o block-qcow.o aes.o block-vmdk.o block-cloop.o block-dmg.o block-bochs.o
>  
>  SOUND_HW = sb16.o
>  AUDIODRV = audio.o noaudio.o wavaudio.o
> Index: block.c
> ===================================================================
> RCS file: /cvsroot/qemu/qemu/block.c,v
> retrieving revision 1.16
> diff -u -r1.16 block.c
> --- block.c	12 Dec 2004 11:24:44 -0000	1.16
> +++ block.c	17 Mar 2005 17:27:00 -0000
> @@ -608,4 +608,5 @@
>      bdrv_register(&bdrv_vmdk);
>      bdrv_register(&bdrv_cloop);
>      bdrv_register(&bdrv_dmg);
> +    bdrv_register(&bdrv_bochs);
>  }
> Index: vl.h
> ===================================================================
> RCS file: /cvsroot/qemu/qemu/vl.h,v
> retrieving revision 1.69
> diff -u -r1.69 vl.h
> --- vl.h	13 Mar 2005 09:43:36 -0000	1.69
> +++ vl.h	17 Mar 2005 17:27:01 -0000
> @@ -381,6 +381,7 @@
>  extern BlockDriver bdrv_vmdk;
>  extern BlockDriver bdrv_cloop;
>  extern BlockDriver bdrv_dmg;
> +extern BlockDriver bdrv_bochs;
>  
>  void bdrv_init(void);
>  BlockDriver *bdrv_find_format(const char *format_name);
> 
> 
> ------------------------------------------------------------------------
> 
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