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Re: [Qemu-devel] [PATCH v5] block:add-cow file format
From: |
Marcelo Tosatti |
Subject: |
Re: [Qemu-devel] [PATCH v5] block:add-cow file format |
Date: |
Tue, 6 Dec 2011 10:48:43 -0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Nov 15, 2011 at 01:28:51PM +0800, Dong Xu Wang wrote:
> From: Dong Xu Wang <address@hidden>
>
> Provide a new file format: add-cow. The usage can be found in add-cow.txt of
> this patch.
>
> Signed-off-by: Dong Xu Wang <address@hidden>
> ---
> Makefile.objs | 1 +
> block.c | 2 +-
> block.h | 1 +
> block/add-cow.c | 417
> ++++++++++++++++++++++++++++++++++++++++++++++++
> block_int.h | 1 +
> docs/specs/add-cow.txt | 57 +++++++
> 6 files changed, 478 insertions(+), 1 deletions(-)
> create mode 100644 block/add-cow.c
> create mode 100644 docs/specs/add-cow.txt
>
> diff --git a/Makefile.objs b/Makefile.objs
> index d7a6539..ad99243 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -31,6 +31,7 @@ block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
>
> block-nested-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o
> vpc.o vvfat.o
> block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o
> qcow2-cache.o
> +block-nested-y += add-cow.o
> block-nested-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
> block-nested-y += qed-check.o
> block-nested-y += parallels.o nbd.o blkdebug.o sheepdog.o blkverify.o
> diff --git a/block.c b/block.c
> index 86910b0..a2be27b 100644
> --- a/block.c
> +++ b/block.c
> @@ -106,7 +106,7 @@ int is_windows_drive(const char *filename)
> #endif
>
> /* check if the path starts with "<protocol>:" */
> -static int path_has_protocol(const char *path)
> +int path_has_protocol(const char *path)
> {
> #ifdef _WIN32
> if (is_windows_drive(path) ||
> diff --git a/block.h b/block.h
> index 051a25d..836284f 100644
> --- a/block.h
> +++ b/block.h
> @@ -276,6 +276,7 @@ char *bdrv_snapshot_dump(char *buf, int buf_size,
> QEMUSnapshotInfo *sn);
>
> char *get_human_readable_size(char *buf, int buf_size, int64_t size);
> int path_is_absolute(const char *path);
> +int path_has_protocol(const char *path);
> void path_combine(char *dest, int dest_size,
> const char *base_path,
> const char *filename);
> diff --git a/block/add-cow.c b/block/add-cow.c
> new file mode 100644
> index 0000000..54d30a9
> --- /dev/null
> +++ b/block/add-cow.c
> @@ -0,0 +1,417 @@
> +#include "qemu-common.h"
> +#include "block_int.h"
> +#include "module.h"
> +
> +#define ADD_COW_MAGIC (((uint64_t)'A' << 56) | ((uint64_t)'D' << 48) |
> \
> + ((uint64_t)'D' << 40) | ((uint64_t)'_' << 32) | \
> + ((uint64_t)'C' << 24) | ((uint64_t)'O' << 16) | \
> + ((uint64_t)'W' << 8) | 0xFF)
> +#define ADD_COW_VERSION 1
> +#define ADD_COW_FILE_LEN 1024
> +
> +typedef struct AddCowHeader {
> + uint64_t magic;
> + uint32_t version;
> + char backing_file[ADD_COW_FILE_LEN];
> + char image_file[ADD_COW_FILE_LEN];
> + uint64_t size;
> +} QEMU_PACKED AddCowHeader;
> +
> +typedef struct BDRVAddCowState {
> + char image_file[ADD_COW_FILE_LEN];
> + BlockDriverState *image_hd;
> + uint8_t *bitmap;
> + uint64_t bitmap_size;
> + CoMutex lock;
> +} BDRVAddCowState;
> +
> +static int add_cow_probe(const uint8_t *buf, int buf_size, const char
> *filename)
> +{
> + const AddCowHeader *header = (const void *)buf;
> +
> + if (be64_to_cpu(header->magic) == ADD_COW_MAGIC &&
> + be32_to_cpu(header->version) == ADD_COW_VERSION) {
> + return 100;
> + } else {
> + return 0;
> + }
> +}
> +
> +static int add_cow_open(BlockDriverState *bs, int flags)
> +{
> + AddCowHeader header;
> + int64_t size;
> + char image_filename[ADD_COW_FILE_LEN];
> + int image_flags;
> + BlockDriver *image_drv = NULL;
> + int ret;
> + BDRVAddCowState *state = (BDRVAddCowState *)(bs->opaque);
> +
> + ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
> + if (ret != sizeof(header)) {
> + goto fail;
> + }
> +
> + if (be64_to_cpu(header.magic) != ADD_COW_MAGIC ||
> + be32_to_cpu(header.version) != ADD_COW_VERSION) {
> + ret = -EINVAL;
> + goto fail;
> + }
> +
> + size = be64_to_cpu(header.size);
> + bs->total_sectors = size / BDRV_SECTOR_SIZE;
> +
> + QEMU_BUILD_BUG_ON(sizeof(state->image_file) !=
> sizeof(header.image_file));
> + pstrcpy(bs->backing_file, sizeof(bs->backing_file),
> + header.backing_file);
> + pstrcpy(state->image_file, sizeof(state->image_file),
> + header.image_file);
> +
> + state->bitmap_size = ((bs->total_sectors + 7) >> 3);
> + state->bitmap = g_malloc0(state->bitmap_size);
> +
> + ret = bdrv_pread(bs->file, sizeof(header), state->bitmap,
> + state->bitmap_size);
> + if (ret != state->bitmap_size) {
> + goto fail;
> + }
Reading the entire bitmap in memory is not acceptable, it may be huge.
Better mmap it and use msync(MS_SYNC) when writing it back. This way the
host can free memory easily upon pressure.
> + /* If there is a image_file, must be together with backing_file */
> + if (state->image_file[0] != '\0') {
> + state->image_hd = bdrv_new("");
> +
> + if (path_has_protocol(state->image_file)) {
> + pstrcpy(image_filename, sizeof(image_filename),
> + state->image_file);
> + } else {
> + path_combine(image_filename, sizeof(image_filename),
> + bs->filename, state->image_file);
> + }
> +
> + image_drv = bdrv_find_format("raw");
> + image_flags =
> + (flags & (~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING))) |
> BDRV_O_RDWR;
Why are you modifying flags here?
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Dong Xu Wang, 2011/12/04
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format,
Marcelo Tosatti <=
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Kevin Wolf, 2011/12/06
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Marcelo Tosatti, 2011/12/06
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Marcelo Tosatti, 2011/12/06
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Kevin Wolf, 2011/12/06
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Marcelo Tosatti, 2011/12/06
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Kevin Wolf, 2011/12/06
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Marcelo Tosatti, 2011/12/06
- Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Kevin Wolf, 2011/12/06
Re: [Qemu-devel] [PATCH v5] block:add-cow file format, Kevin Wolf, 2011/12/06