block: Parse 'detect-zeroes' in bdrv_open_common()

Amongst others, this means that you can now use the 'detect-zeroes'
option for non-top-level nodes in blockdev-add, like the QAPI schema
promises.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/block.c b/block.c
index 493ecf3137..1f1045738d 100644
--- a/block.c
+++ b/block.c
@@ -42,6 +42,7 @@
 #include "qapi-event.h"
 #include "qemu/cutils.h"
 #include "qemu/id.h"
+#include "qapi/util.h"
 
 #ifdef CONFIG_BSD
 #include <sys/ioctl.h>
@@ -954,6 +955,11 @@ static QemuOptsList bdrv_runtime_opts = {
             .type = QEMU_OPT_BOOL,
             .help = "Node is opened in read-only mode",
         },
+        {
+            .name = "detect-zeroes",
+            .type = QEMU_OPT_STRING,
+            .help = "try to optimize zero writes (off, on, unmap)",
+        },
         { /* end of list */ }
     },
 };
@@ -970,6 +976,7 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
     const char *filename;
     const char *driver_name = NULL;
     const char *node_name = NULL;
+    const char *detect_zeroes;
     QemuOpts *opts;
     BlockDriver *drv;
     Error *local_err = NULL;
@@ -1038,6 +1045,32 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
         }
     }
 
+    detect_zeroes = qemu_opt_get(opts, "detect-zeroes");
+    if (detect_zeroes) {
+        BlockdevDetectZeroesOptions value =
+            qapi_enum_parse(BlockdevDetectZeroesOptions_lookup,
+                            detect_zeroes,
+                            BLOCKDEV_DETECT_ZEROES_OPTIONS__MAX,
+                            BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF,
+                            &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            ret = -EINVAL;
+            goto fail_opts;
+        }
+
+        if (value == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
+            !(bs->open_flags & BDRV_O_UNMAP))
+        {
+            error_setg(errp, "setting detect-zeroes to unmap is not allowed "
+                             "without setting discard operation to unmap");
+            ret = -EINVAL;
+            goto fail_opts;
+        }
+
+        bs->detect_zeroes = value;
+    }
+
     if (filename != NULL) {
         pstrcpy(bs->filename, sizeof(bs->filename), filename);
     } else {