[Qemu-devel] [PATCH v2 2/3] block.c: adding bdrv_delete_file

[Daniel Henrique Barboza]

Using the new 'bdrv_co_delete_file' interface, bdrv_delete_file
can be used in a way similar of the existing bdrv_create_file to
invoke a driver, given by a format @fmt, to clean up a created
file.

The logic is also similar to what is already done in bdrv_create_file:
a qemu_coroutine is created if needed, a specialized function
bdrv_delete_co_entry is used to call the bdrv_co_delete_file
co-routine of the driver, if the driver implements it.

Suggested-by: Daniel P. Berrangé <address@hidden>
Signed-off-by: Daniel Henrique Barboza <address@hidden>
---

@Daniel: I put the 'Suggested-by' tag here aware that what is being
done in this patch wasn't explicitly suggested by you in that review.
However, since it's a consequence of your suggestion, here it is.

If you mind the tag here, let me know and we can remove it.


 block.c               | 72 +++++++++++++++++++++++++++++++++++++++++++
 include/block/block.h |  3 ++
 2 files changed, 75 insertions(+)

diff --git a/block.c b/block.c
index 2b632baba2..5c7781e471 100644
--- a/block.c
+++ b/block.c
@@ -592,6 +592,78 @@ done:
     return ret;
 }
 
+static void coroutine_fn bdrv_delete_co_entry(void *opaque)
+{
+    Error *local_err = NULL;
+    int ret;
+
+    CreateCo *cco = opaque;
+    assert(cco->drv);
+
+    ret = cco->drv->bdrv_co_delete_file(cco->filename, &local_err);
+    error_propagate(&cco->err, local_err);
+    cco->ret = ret;
+}
+
+int bdrv_delete_file(const char *filename, const char *fmt,
+                     Error **errp)
+{
+
+    BlockDriver *drv = bdrv_find_format(fmt);
+    Coroutine *co;
+    CreateCo cco = {
+        .drv = drv,
+        .filename = g_strdup(filename),
+        .ret = NOT_DONE,
+        .err = NULL,
+    };
+    int ret;
+
+    if (!drv) {
+        error_setg(errp, "Unknown file format '%s'", fmt);
+        ret = -ENOENT;
+        goto out;
+    }
+
+    if (!drv->bdrv_co_delete_file) {
+        error_setg(errp, "Driver '%s' does not support image delete",
+                   drv->format_name);
+        ret = -ENOTSUP;
+        goto out;
+    }
+
+    if (!drv->bdrv_co_delete_file) {
+        error_setg(errp, "Driver '%s' does not support image delete",
+                   drv->format_name);
+        ret = -ENOTSUP;
+        goto out;
+    }
+
+    if (qemu_in_coroutine()) {
+        /* Fast-path if already in coroutine context */
+        bdrv_delete_co_entry(&cco);
+    } else {
+        co = qemu_coroutine_create(bdrv_delete_co_entry, &cco);
+        qemu_coroutine_enter(co);
+        while (cco.ret == NOT_DONE) {
+            aio_poll(qemu_get_aio_context(), true);
+        }
+    }
+
+    ret = cco.ret;
+    if (ret < 0) {
+        if (cco.err) {
+            error_propagate(errp, cco.err);
+        } else {
+            error_setg_errno(errp, -ret, "Could not delete image");
+        }
+    }
+
+out:
+    g_free(cco.filename);
+    return ret;
+}
+
 /**
  * Try to get @bs's logical and physical block size.
  * On success, store them in @bsz struct and return 0.
diff --git a/include/block/block.h b/include/block/block.h
index efb77daf9f..9b66cf00cb 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -366,6 +366,9 @@ void bdrv_unfreeze_backing_chain(BlockDriverState *bs, 
BlockDriverState *base);
 bool bdrv_path_is_regular_file(const char *path);
 int coroutine_fn bdrv_co_delete_file_generic(const char *filename,
                                              Error **errp);
+int bdrv_delete_file(const char *filename, const char *fmt,
+                     Error **errp);
+
 
 typedef struct BdrvCheckResult {
     int corruptions;
-- 
2.20.1