Am 06.12.2011 13:48, schrieb Marcelo Tosatti: > On Tue, Nov 15, 2011 at 01:28:51PM +0800, Dong Xu Wang wrote: >> From: Dong Xu Wang <wdon...@linux.vnet.ibm.com> >> >> 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 <wdon...@linux.vnet.ibm.com> >> --- >> 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.
You can't use mmap in block drivers. It would only work with raw-posix backends, if at all. Kevin