Commit 2063392a authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Kevin Wolf
Browse files

cow: use qemu block API 



Use bdrv_pwrite to access the backing device instead of pread, and
convert the driver to implementing the bdrv_open method which gives
it an already opened BlockDriverState for the underlying device.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 893a9cb4

block/cow.c

+13 −26
Original line number Diff line number Diff line
@@ -42,7 +42,6 @@ struct cow_header_v2 { 
};



typedef struct BDRVCowState {

    int fd;

    int64_t cow_sectors_offset;

} BDRVCowState;
@@ -58,23 +57,16 @@ static int cow_probe(const uint8_t *buf, int buf_size, const char *filename) 
        return 0;

}



static int cow_open(BlockDriverState *bs, const char *filename, int flags)

static int cow_open(BlockDriverState *bs, int flags)

{

    BDRVCowState *s = bs->opaque;

    int fd;

    struct cow_header_v2 cow_header;

    int bitmap_size;

    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;

    }

    s->fd = fd;

    /* see if it is a cow image */

    if (pread(fd, &cow_header, sizeof(cow_header), 0) != sizeof(cow_header)) {

    if (bdrv_pread(bs->file, 0, &cow_header, sizeof(cow_header)) !=

            sizeof(cow_header)) {

        goto fail;

    }
@@ -94,7 +86,6 @@ static int cow_open(BlockDriverState *bs, const char *filename, int flags) 
    s->cow_sectors_offset = (bitmap_size + 511) & ~511;

    return 0;

 fail:

    close(fd);

    return -1;

}
@@ -104,18 +95,17 @@ static int cow_open(BlockDriverState *bs, const char *filename, int flags) 
 */

static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)

{

    BDRVCowState *s = bs->opaque;

    uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;

    uint8_t bitmap;



    if (pread(s->fd, &bitmap, sizeof(bitmap), offset) !=

    if (bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap)) !=

	    sizeof(bitmap)) {

       return -errno;

    }



    bitmap |= (1 << (bitnum % 8));



    if (pwrite(s->fd, &bitmap, sizeof(bitmap), offset) !=

    if (bdrv_pwrite(bs->file, offset, &bitmap, sizeof(bitmap)) !=

	    sizeof(bitmap)) {

       return -errno;

    }
@@ -124,11 +114,10 @@ static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum) 


static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum)

{

    BDRVCowState *s = bs->opaque;

    uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;

    uint8_t bitmap;



    if (pread(s->fd, &bitmap, sizeof(bitmap), offset) !=

    if (bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap)) !=

	    sizeof(bitmap)) {

       return -errno;

    }
@@ -186,8 +175,9 @@ static int cow_read(BlockDriverState *bs, int64_t sector_num, 


    while (nb_sectors > 0) {

        if (cow_is_allocated(bs, sector_num, nb_sectors, &n)) {

            ret = pread(s->fd, buf, n * 512,

                        s->cow_sectors_offset + sector_num * 512);

            ret = bdrv_pread(bs->file,

                        s->cow_sectors_offset + sector_num * 512,

                        buf, n * 512);

            if (ret != n * 512)

                return -1;

        } else {
@@ -213,8 +203,8 @@ static int cow_write(BlockDriverState *bs, int64_t sector_num, 
    BDRVCowState *s = bs->opaque;

    int ret;



    ret = pwrite(s->fd, buf, nb_sectors * 512,

                 s->cow_sectors_offset + sector_num * 512);

    ret = bdrv_pwrite(bs->file, s->cow_sectors_offset + sector_num * 512,

                      buf, nb_sectors * 512);

    if (ret != nb_sectors * 512)

        return -1;
@@ -223,8 +213,6 @@ static int cow_write(BlockDriverState *bs, int64_t sector_num, 


static void cow_close(BlockDriverState *bs)

{

    BDRVCowState *s = bs->opaque;

    close(s->fd);

}



static int cow_create(const char *filename, QEMUOptionParameter *options)
@@ -294,8 +282,7 @@ exit: 


static void cow_flush(BlockDriverState *bs)

{

    BDRVCowState *s = bs->opaque;

    qemu_fdatasync(s->fd);

    bdrv_flush(bs->file);

}



static QEMUOptionParameter cow_create_options[] = {
@@ -316,7 +303,7 @@ static BlockDriver bdrv_cow = { 
    .format_name	= "cow",

    .instance_size	= sizeof(BDRVCowState),

    .bdrv_probe		= cow_probe,

    .bdrv_file_open	= cow_open,

    .bdrv_open		= cow_open,

    .bdrv_read		= cow_read,

    .bdrv_write		= cow_write,

    .bdrv_close		= cow_close,