于Fri 09 Sep 2011 10:27:26 PM CST,Kevin Wolf写到:
Am 09.09.2011 07:48, schrieb Dong Xu Wang:
As raw file format does not support backing_file and copy on write feature, so
I add COW to it to support backing_file option. I store dirty bitmap in an
add-cow file. When executed, it looks like this:
qemu-img create -f add-cow -o backing_file=ubuntu.img,image_file=test.img
test.add-cow
qemu -drive if=virtio,file=test.add-cow -m 1024
(test.img is a raw format file; test.add-cow stores bitmap)
Signed-off-by: Dong Xu Wang <wdon...@linux.vnet.ibm.com>
You should not make any changes to generic code, except maybe add
something to bdrv_get_info(). In particular you shouldn't need to touch
bdrv_open() or bdrv_create() at all.
The one required change in the approach for this to work is that you
shouldn't view raw+add_cow as a unit, but add_cow should be treated as
something separate that happens to be stacked on a raw file (which is
created separately).
Then you can do almost everything in block/add-cow.c.
---
Makefile.objs | 1 +
block.c | 83 ++++++++++-
block.h | 2 +
block/add-cow.c | 456 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
block_int.h | 6 +
qemu-img.c | 10 ++
6 files changed, 555 insertions(+), 3 deletions(-)
create mode 100644 block/add-cow.c
diff --git a/Makefile.objs b/Makefile.objs
index 26b885b..1402f9f 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 a8c789a..c797cfc 100644
--- a/block.c
+++ b/block.c
@@ -369,7 +369,7 @@ static int find_image_format(const char *filename,
BlockDriver **pdrv)
{
int ret, score, score_max;
BlockDriver *drv1, *drv;
- uint8_t buf[2048];
+ uint8_t buf[4096];
BlockDriverState *bs;
What's the reason for this change?
The size of add_cow_header in my code is larger than 2048.
diff --git a/block/add-cow.c b/block/add-cow.c
new file mode 100644
index 0000000..f4b67e5
--- /dev/null
+++ b/block/add-cow.c
@@ -0,0 +1,456 @@
+#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
+
+struct add_cow_header {
+ uint64_t magic;
+ uint32_t version;
+ char backing_file[1024];
+ char image_file[1024];
+ uint64_t size;
+ uint32_t sectorsize;
+} add_cow_header;
QEMU_PACKED
Sorry, what does QEMU_PACKED mean?
+typedef struct BDRVAddCowState {
+ CoMutex lock;
+ CoMutex bitmap_lock;
+} BDRVAddCowState;
+
+typedef struct AddCowAIOCB {
+ BlockDriverAIOCB common;
+ int64_t sector_num;
+ QEMUIOVector *qiov;
+ int remaining_sectors;
+ int cur_nr_sectors;
+ uint64_t bytes_done;
+ bool is_write;
+ QEMUIOVector hd_qiov;
+ QEMUBH *bh;
+
+} AddCowAIOCB;
You shouldn't be using AIOCBs with a coroutine-based block driver.
Instead you should just use variables on the stack and function parameters.
+static int add_cow_flush(BlockDriverState *bs)
+{
+ return bdrv_flush(bs->file);
+}
What about bs->image_hd?
@@ -208,6 +209,11 @@ struct BlockDriverState {
int in_use; /* users other than guest access, eg. block migration */
QTAILQ_ENTRY(BlockDriverState) list;
void *private;
+
+ char image_file[1024];
+ BlockDriverState *image_hd;
+ uint8_t *bitmap;
+ uint64_t bitmap_size;
};
These belong in BDRVAddCowState.
Kevin
Thanks for your comments Kevin, I will produce a second version soon.
