Commit 122bb9e3 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Kevin Wolf
Browse files

cow: use pread/pwrite 



Use pread/pwrite instead of lseek + read/write in preparation of using the
qemu block API.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 68dba0bf

block/cow.c

+5 −5
Original line number Diff line number Diff line
@@ -78,7 +78,7 @@ static int cow_open(BlockDriverState *bs, const char *filename, int flags) 
    }

    s->fd = fd;

    /* see if it is a cow image */

    if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {

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

        goto fail;

    }
@@ -159,8 +159,8 @@ static int cow_read(BlockDriverState *bs, int64_t sector_num, 


    while (nb_sectors > 0) {

        if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {

            lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);

            ret = read(s->fd, buf, n * 512);

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

                        s->cow_sectors_offset + sector_num * 512);

            if (ret != n * 512)

                return -1;

        } else {
@@ -186,8 +186,8 @@ static int cow_write(BlockDriverState *bs, int64_t sector_num, 
    BDRVCowState *s = bs->opaque;

    int ret, i;



    lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);

    ret = write(s->fd, buf, nb_sectors * 512);

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

                 s->cow_sectors_offset + sector_num * 512);

    if (ret != nb_sectors * 512)

        return -1;

    for (i = 0; i < nb_sectors; i++)