Revert "Make default invocation of block drivers safer (v3)"

This reverts commit 79368c81.

Conflicts:

	block.c

I haven't been able to come up with a solution yet for the corruption caused by
unaligned requests from the IDE disk so revert until a solution can be written.
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 8b33d9ee)

block.c

@@ -523,7 +523,6 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
               BlockDriver *drv)
 {
     int ret;
-    int probed = 0;
 
     if (flags & BDRV_O_SNAPSHOT) {
         BlockDriverState *bs1;
@@ -584,7 +583,6 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
     /* Find the right image format driver */
     if (!drv) {
         ret = find_image_format(filename, &drv);
-        probed = 1;
     }
 
     if (!drv) {
@@ -597,8 +595,6 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
         goto unlink_and_fail;
     }
 
-    bs->probed = probed;
-
     /* If there is a backing file, use it */
     if ((flags & BDRV_O_NO_BACKING) == 0 && bs->backing_file[0] != '\0') {
         char backing_filename[PATH_MAX];

block/raw.c

@@ -9,82 +9,15 @@ static int raw_open(BlockDriverState *bs, int flags)
     return 0;
 }
 
-/* check for the user attempting to write something that looks like a
-   block format header to the beginning of the image and fail out.
-*/
-static int check_for_block_signature(BlockDriverState *bs, const uint8_t *buf)
-{
-    static const uint8_t signatures[][4] = {
-        { 'Q', 'F', 'I', 0xfb }, /* qcow/qcow2 */
-        { 'C', 'O', 'W', 'D' }, /* VMDK3 */
-        { 'V', 'M', 'D', 'K' }, /* VMDK4 */
-        { 'O', 'O', 'O', 'M' }, /* UML COW */
-        {}
-    };
-    int i;
-
-    for (i = 0; signatures[i][0] != 0; i++) {
-        if (memcmp(buf, signatures[i], 4) == 0) {
-            return 1;
-        }
-    }
-
-    return 0;
-}
-
-static int check_write_unsafe(BlockDriverState *bs, int64_t sector_num,
-                              const uint8_t *buf, int nb_sectors)
-{
-    /* assume that if the user specifies the format explicitly, then assume
-       that they will continue to do so and provide no safety net */
-    if (!bs->probed) {
-        return 0;
-    }
-
-    if (sector_num == 0 && nb_sectors > 0) {
-        return check_for_block_signature(bs, buf);
-    }
-
-    return 0;
-}
-
 static int raw_read(BlockDriverState *bs, int64_t sector_num,
                     uint8_t *buf, int nb_sectors)
 {
     return bdrv_read(bs->file, sector_num, buf, nb_sectors);
 }
 
-static int raw_write_scrubbed_bootsect(BlockDriverState *bs,
-                                       const uint8_t *buf)
-{
-    uint8_t bootsect[512];
-
-    /* scrub the dangerous signature */
-    memcpy(bootsect, buf, 512);
-    memset(bootsect, 0, 4);
-
-    return bdrv_write(bs->file, 0, bootsect, 1);
-}
-
 static int raw_write(BlockDriverState *bs, int64_t sector_num,
                      const uint8_t *buf, int nb_sectors)
 {
-    if (check_write_unsafe(bs, sector_num, buf, nb_sectors)) {
-        int ret;
-
-        ret = raw_write_scrubbed_bootsect(bs, buf);
-        if (ret < 0) {
-            return ret;
-        }
-
-        ret = bdrv_write(bs->file, 1, buf + 512, nb_sectors - 1);
-        if (ret < 0) {
-            return ret;
-        }
-
-        return ret + 512;
-    }
-
     return bdrv_write(bs->file, sector_num, buf, nb_sectors);
 }
 
@@ -95,73 +28,10 @@ static BlockDriverAIOCB *raw_aio_readv(BlockDriverState *bs,
     return bdrv_aio_readv(bs->file, sector_num, qiov, nb_sectors, cb, opaque);
 }
 
-typedef struct RawScrubberBounce
-{
-    BlockDriverCompletionFunc *cb;
-    void *opaque;
-    QEMUIOVector qiov;
-} RawScrubberBounce;
-
-static void raw_aio_writev_scrubbed(void *opaque, int ret)
-{
-    RawScrubberBounce *b = opaque;
-
-    if (ret < 0) {
-        b->cb(b->opaque, ret);
-    } else {
-        b->cb(b->opaque, ret + 512);
-    }
-
-    qemu_iovec_destroy(&b->qiov);
-    qemu_free(b);
-}
-
 static BlockDriverAIOCB *raw_aio_writev(BlockDriverState *bs,
     int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
     BlockDriverCompletionFunc *cb, void *opaque)
 {
-    const uint8_t *first_buf;
-    int first_buf_index = 0, i;
-
-    /* This is probably being paranoid, but handle cases of zero size
-       vectors. */
-    for (i = 0; i < qiov->niov; i++) {
-        if (qiov->iov[i].iov_len) {
-            assert(qiov->iov[i].iov_len >= 512);
-            first_buf_index = i;
-            break;
-        }
-    }
-
-    first_buf = qiov->iov[first_buf_index].iov_base;
-
-    if (check_write_unsafe(bs, sector_num, first_buf, nb_sectors)) {
-        RawScrubberBounce *b;
-        int ret;
-
-        /* write the first sector using sync I/O */
-        ret = raw_write_scrubbed_bootsect(bs, first_buf);
-        if (ret < 0) {
-            return NULL;
-        }
-
-        /* adjust request to be everything but first sector */
-
-        b = qemu_malloc(sizeof(*b));
-        b->cb = cb;
-        b->opaque = opaque;
-
-        qemu_iovec_init(&b->qiov, qiov->nalloc);
-        qemu_iovec_concat(&b->qiov, qiov, qiov->size);
-
-        b->qiov.size -= 512;
-        b->qiov.iov[first_buf_index].iov_base += 512;
-        b->qiov.iov[first_buf_index].iov_len -= 512;
-
-        return bdrv_aio_writev(bs->file, sector_num + 1, &b->qiov,
-                               nb_sectors - 1, raw_aio_writev_scrubbed, b);
-    }
-
     return bdrv_aio_writev(bs->file, sector_num, qiov, nb_sectors, cb, opaque);
 }
 

block_int.h

@@ -148,7 +148,6 @@ struct BlockDriverState {
     int encrypted; /* if true, the media is encrypted */
     int valid_key; /* if true, a valid encryption key has been set */
     int sg;        /* if true, the device is a /dev/sg* */
-    int probed;    /* if true, format was probed automatically */
     /* event callback when inserting/removing */
     void (*change_cb)(void *opaque);
     void *change_opaque;