diff options
| author | Daniel P. Berrange <berrange@redhat.com> | 2016-03-21 14:11:42 +0000 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2016-03-30 11:59:32 +0200 |
| commit | abb06c5ac1c86e747bbe08bf7b5b69723ad69832 (patch) | |
| tree | 227d67569c4069dbb356410cbf77e0544224bda8 /block | |
| parent | 543021569978c908fccff235bf90fc803e6fed1d (diff) | |
block: add flag to indicate that no I/O will be performed
When opening an image it is useful to know whether the caller
intends to perform I/O on the image or not. In the case of
encrypted images this will allow the block driver to avoid
having to prompt for decryption keys when we merely want to
query header metadata about the image. eg qemu-img info
This flag is enforced at the top level only, since even if
we don't want todo I/O on the 'qcow2' file payload, the
underlying 'file' driver will still need todo I/O to read
the qcow2 header, for example.
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/io.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/block/io.c b/block/io.c index c2611e53c8..4520cab852 100644 --- a/block/io.c +++ b/block/io.c @@ -844,6 +844,7 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs, assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0); assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0); assert(!qiov || bytes == qiov->size); + assert((bs->open_flags & BDRV_O_NO_IO) == 0); /* Handle Copy on Read and associated serialisation */ if (flags & BDRV_REQ_COPY_ON_READ) { @@ -1130,6 +1131,7 @@ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs, assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0); assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0); assert(!qiov || bytes == qiov->size); + assert((bs->open_flags & BDRV_O_NO_IO) == 0); waited = wait_serialising_requests(req); assert(!waited || !req->serialising); |