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
Signed-off-by: Daniel P. Berrange
---
block.c | 5 +++--
block/io.c| 2 ++
include/block/block.h | 1 +
qemu-img.c| 44 ++--
4 files changed, 28 insertions(+), 24 deletions(-)
diff --git a/block.c b/block.c
index 59a18a3..4d1a9d3 100644
--- a/block.c
+++ b/block.c
@@ -706,7 +706,8 @@ static void bdrv_inherited_options(int *child_flags, QDict
*child_options,
flags |= BDRV_O_UNMAP;
/* Clear flags that only apply to the top layer */
-flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING | BDRV_O_COPY_ON_READ);
+flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING | BDRV_O_COPY_ON_READ |
+ BDRV_O_NO_IO);
*child_flags = flags;
}
@@ -726,7 +727,7 @@ static void bdrv_inherited_fmt_options(int *child_flags,
QDict *child_options,
child_file.inherit_options(child_flags, child_options,
parent_flags, parent_options);
-*child_flags &= ~BDRV_O_PROTOCOL;
+*child_flags &= ~(BDRV_O_PROTOCOL | BDRV_O_NO_IO);
}
const BdrvChildRole child_format = {
diff --git a/block/io.c b/block/io.c
index a69bfc4..010e25a 100644
--- a/block/io.c
+++ b/block/io.c
@@ -862,6 +862,7 @@ 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) {
@@ -1148,6 +1149,7 @@ 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);
diff --git a/include/block/block.h b/include/block/block.h
index eaa6426..bb8e97d 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -93,6 +93,7 @@ typedef struct HDGeometry {
#define BDRV_O_PROTOCOL0x8000 /* if no block driver is explicitly given:
select an appropriate protocol driver,
ignoring the format layer */
+#define BDRV_O_NO_IO 0x1 /* don't initialize for I/O */
#define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH)
diff --git a/qemu-img.c b/qemu-img.c
index 3103150..a03e501 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -224,13 +224,13 @@ static int print_block_option_help(const char *filename,
const char *fmt)
static int img_open_password(BlockBackend *blk, const char *filename,
- bool require_io, bool quiet)
+ int flags, bool quiet)
{
BlockDriverState *bs;
char password[256];
bs = blk_bs(blk);
-if (bdrv_is_encrypted(bs) && require_io) {
+if (bdrv_is_encrypted(bs) && !(flags & BDRV_O_NO_IO)) {
qprintf(quiet, "Disk image '%s' is encrypted.\n", filename);
if (qemu_read_password(password, sizeof(password)) < 0) {
error_report("No password given");
@@ -248,7 +248,7 @@ static int img_open_password(BlockBackend *blk, const char
*filename,
static BlockBackend *img_open_opts(const char *id,
const char *optstr,
QemuOpts *opts, int flags,
- bool require_io, bool quiet)
+ bool quiet)
{
QDict *options;
Error *local_err = NULL;
@@ -260,7 +260,7 @@ static BlockBackend *img_open_opts(const char *id,
return NULL;
}
-if (img_open_password(blk, optstr, require_io, quiet) < 0) {
+if (img_open_password(blk, optstr, flags, quiet) < 0) {
blk_unref(blk);
return NULL;
}
@@ -269,7 +269,7 @@ static BlockBackend *img_open_opts(const char *id,
static BlockBackend *img_open_file(const char *id, const char *filename,
const char *fmt, int flags,
- bool require_io, bool quiet)
+ bool quiet)
{
BlockBackend *blk;
Error *local_err = NULL;
@@ -286,7 +286,7 @@ static BlockBackend *img_open_file(const char *id, c
