block: Add blk_new_with_bs() helper

There are several callers that need to create a new block backend from
an existing BDS; make the task slightly easier with a common helper
routine.

Suggested-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200424190903.522087-2-eblake@redhat.com>
[mreitz: Set @ret only in error paths, see
 https://lists.nongnu.org/archive/html/qemu-block/2020-04/msg01216.html]
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200428192648.749066-2-eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

14 files changed, 75 insertions, 59 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 17ed6d8c5b..f4944861fa 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -356,6 +356,29 @@ BlockBackend *blk_new(AioContext *ctx, uint64_t perm, uint64_t shared_perm)
 }
 
 /*
+ * Create a new BlockBackend connected to an existing BlockDriverState.
+ *
+ * @perm is a bitmasks of BLK_PERM_* constants which describes the
+ * permissions to request for @bs that is attached to this
+ * BlockBackend.  @shared_perm is a bitmask which describes which
+ * permissions may be granted to other users of the attached node.
+ * Both sets of permissions can be changed later using blk_set_perm().
+ *
+ * Return the new BlockBackend on success, null on failure.
+ */
+BlockBackend *blk_new_with_bs(BlockDriverState *bs, uint64_t perm,
+                              uint64_t shared_perm, Error **errp)
+{
+    BlockBackend *blk = blk_new(bdrv_get_aio_context(bs), perm, shared_perm);
+
+    if (blk_insert_bs(blk, bs, errp) < 0) {
+        blk_unref(blk);
+        return NULL;
+    }
+    return blk;
+}
+
+/*
  * Creates a new BlockBackend, opens a new BlockDriverState, and connects both.
  * The new BlockBackend is in the main AioContext.
  *
diff --git a/block/crypto.c b/block/crypto.c
index e02f343590..ca44dae4f7 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -261,11 +261,10 @@ static int block_crypto_co_create_generic(BlockDriverState *bs,
     QCryptoBlock *crypto = NULL;
     struct BlockCryptoCreateData data;
 
-    blk = blk_new(bdrv_get_aio_context(bs),
-                  BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
-
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
+    blk = blk_new_with_bs(bs, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL,
+                          errp);
+    if (!blk) {
+        ret = -EPERM;
         goto cleanup;
     }
 
diff --git a/block/parallels.c b/block/parallels.c
index 2be92cf417..8db64a55e3 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -559,10 +559,10 @@ static int coroutine_fn parallels_co_create(BlockdevCreateOptions* opts,
         return -EIO;
     }
 
-    blk = blk_new(bdrv_get_aio_context(bs),
-                  BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
+    blk = blk_new_with_bs(bs, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL,
+                          errp);
+    if (!blk) {
+        ret = -EPERM;
         goto out;
     }
     blk_set_allow_write_beyond_eof(blk, true);
diff --git a/block/qcow.c b/block/qcow.c
index 6b5f2269f0..b0475b73a5 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -849,10 +849,10 @@ static int coroutine_fn qcow_co_create(BlockdevCreateOptions *opts,
         return -EIO;
     }
 
-    qcow_blk = blk_new(bdrv_get_aio_context(bs),
-                       BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
-    ret = blk_insert_bs(qcow_blk, bs, errp);
-    if (ret < 0) {
+    qcow_blk = blk_new_with_bs(bs, BLK_PERM_WRITE | BLK_PERM_RESIZE,
+                               BLK_PERM_ALL, errp);
+    if (!qcow_blk) {
+        ret = -EPERM;
         goto exit;
     }
     blk_set_allow_write_beyond_eof(qcow_blk, true);
diff --git a/block/qcow2.c b/block/qcow2.c
index 2ba0b17c39..0edc7f4643 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3405,10 +3405,10 @@ qcow2_co_create(BlockdevCreateOptions *create_options, Error **errp)
     }
 
     /* Create BlockBackend to write to the image */
-    blk = blk_new(bdrv_get_aio_context(bs),
-                  BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
+    blk = blk_new_with_bs(bs, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL,
+                          errp);
+    if (!blk) {
+        ret = -EPERM;
         goto out;
     }
     blk_set_allow_write_beyond_eof(blk, true);
@@ -5412,12 +5412,10 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
     }
 
     if (new_size) {
-        BlockBackend *blk = blk_new(bdrv_get_aio_context(bs),
-                                    BLK_PERM_RESIZE, BLK_PERM_ALL);
-        ret = blk_insert_bs(blk, bs, errp);
-        if (ret < 0) {
-            blk_unref(blk);
-            return ret;
+        BlockBackend *blk = blk_new_with_bs(bs, BLK_PERM_RESIZE, BLK_PERM_ALL,
+                                            errp);
+        if (!blk) {
+            return -EPERM;
         }
 
         /*
diff --git a/block/qed.c b/block/qed.c
index b0fdb8f565..fb609cfba1 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -651,10 +651,10 @@ static int coroutine_fn bdrv_qed_co_create(BlockdevCreateOptions *opts,
         return -EIO;
     }
 
-    blk = blk_new(bdrv_get_aio_context(bs),
-                  BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
+    blk = blk_new_with_bs(bs, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL,
+                          errp);
+    if (!blk) {
+        ret = -EPERM;
         goto out;
     }
     blk_set_allow_write_beyond_eof(blk, true);
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 76729f40a4..2eb61938ff 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -1803,12 +1803,12 @@ static int sd_prealloc(BlockDriverState *bs, int64_t old_size, int64_t new_size,
     void *buf = NULL;
     int ret;
 
-    blk = blk_new(bdrv_get_aio_context(bs),
-                  BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | BLK_PERM_RESIZE,
-                  BLK_PERM_ALL);
+    blk = blk_new_with_bs(bs,
+                          BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | BLK_PERM_RESIZE,
+                          BLK_PERM_ALL, errp);
 
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
+    if (!blk) {
+        ret = -EPERM;
         goto out_with_err_set;
     }
 
diff --git a/block/vdi.c b/block/vdi.c
index 0c7835ae70..2d28046615 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -804,10 +804,10 @@ static int coroutine_fn vdi_co_do_create(BlockdevCreateOptions *create_options,
         goto exit;
     }
 
-    blk = blk_new(bdrv_get_aio_context(bs_file),
-                  BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
-    ret = blk_insert_bs(blk, bs_file, errp);
-    if (ret < 0) {
+    blk = blk_new_with_bs(bs_file, BLK_PERM_WRITE | BLK_PERM_RESIZE,
+                          BLK_PERM_ALL, errp);
+    if (!blk) {
+        ret = -EPERM;
         goto exit;
     }
 
diff --git a/block/vhdx.c b/block/vhdx.c
index 45be0a4321..9d3951f4ee 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1984,10 +1984,10 @@ static int coroutine_fn vhdx_co_create(BlockdevCreateOptions *opts,
         return -EIO;
     }
 
-    blk = blk_new(bdrv_get_aio_context(bs),
-                  BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
+    blk = blk_new_with_bs(bs, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL,
+                          errp);
+    if (!blk) {
+        ret = -EPERM;
         goto delete_and_exit;
     }
     blk_set_allow_write_beyond_eof(blk, true);
diff --git a/block/vmdk.c b/block/vmdk.c
index 8ec18f35a5..b02fdd14b2 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -2717,11 +2717,10 @@ static BlockBackend *vmdk_co_create_cb(int64_t size, int idx,
     if (!bs) {
         return NULL;
     }
-    blk = blk_new(bdrv_get_aio_context(bs),
-                  BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | BLK_PERM_RESIZE,
-                  BLK_PERM_ALL);
-    if (blk_insert_bs(blk, bs, errp)) {
-        bdrv_unref(bs);
+    blk = blk_new_with_bs(bs,
+                          BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | BLK_PERM_RESIZE,
+                          BLK_PERM_ALL, errp);
+    if (!blk) {
         return NULL;
     }
     blk_set_allow_write_beyond_eof(blk, true);
diff --git a/block/vpc.c b/block/vpc.c
index 2d1eade146..5e31dd1e47 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -1012,10 +1012,10 @@ static int coroutine_fn vpc_co_create(BlockdevCreateOptions *opts,
         return -EIO;
     }
 
-    blk = blk_new(bdrv_get_aio_context(bs),
-                  BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
+    blk = blk_new_with_bs(bs, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL,
+                          errp);
+    if (!blk) {
+        ret = -EPERM;
         goto out;
     }
     blk_set_allow_write_beyond_eof(blk, true);
diff --git a/blockdev.c b/blockdev.c
index dc1a0c7c2f..b3c840ec03 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2711,7 +2711,6 @@ void qmp_block_resize(bool has_device, const char *device,
     BlockBackend *blk = NULL;
     BlockDriverState *bs;
     AioContext *aio_context;
-    int ret;
 
     bs = bdrv_lookup_bs(has_device ? device : NULL,
                         has_node_name ? node_name : NULL,
@@ -2734,14 +2733,13 @@ void qmp_block_resize(bool has_device, const char *device,
         goto out;
     }
 
-    blk = blk_new(bdrv_get_aio_context(bs), BLK_PERM_RESIZE, BLK_PERM_ALL);
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
+    blk = blk_new_with_bs(bs, BLK_PERM_RESIZE, BLK_PERM_ALL, errp);
+    if (!blk) {
         goto out;
     }
 
     bdrv_drained_begin(bs);
-    ret = blk_truncate(blk, size, false, PREALLOC_MODE_OFF, 0, errp);
+    blk_truncate(blk, size, false, PREALLOC_MODE_OFF, 0, errp);
     bdrv_drained_end(bs);
 
 out:
diff --git a/blockjob.c b/blockjob.c
index fc850312c1..2affa1844d 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -397,16 +397,13 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
 {
     BlockBackend *blk;
     BlockJob *job;
-    int ret;
 
     if (job_id == NULL && !(flags & JOB_INTERNAL)) {
         job_id = bdrv_get_device_name(bs);
     }
 
-    blk = blk_new(bdrv_get_aio_context(bs), perm, shared_perm);
-    ret = blk_insert_bs(blk, bs, errp);
-    if (ret < 0) {
-        blk_unref(blk);
+    blk = blk_new_with_bs(bs, perm, shared_perm, errp);
+    if (!blk) {
         return NULL;
     }
 
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 34de7faa81..0917663d89 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -77,6 +77,8 @@ typedef struct BlockBackendPublic {
 } BlockBackendPublic;
 
 BlockBackend *blk_new(AioContext *ctx, uint64_t perm, uint64_t shared_perm);
+BlockBackend *blk_new_with_bs(BlockDriverState *bs, uint64_t perm,
+                              uint64_t shared_perm, Error **errp);
 BlockBackend *blk_new_open(const char *filename, const char *reference,
                            QDict *options, int flags, Error **errp);
 int blk_get_refcnt(BlockBackend *blk);