block: introduce bdrv_open_file_child() helper

Almost all drivers call bdrv_open_child() similarly. Let's create a
helper for this.

The only not updated drivers that call bdrv_open_child() to set
bs->file are raw-format and snapshot-access:
    raw-format sometimes want to have filtered child but
        don't set drv->is_filter to true.
    snapshot-access wants only DATA | PRIMARY

Possibly we should implement drv->is_filter_func() handler, to consider
raw-format as filter when it works as filter.. But it's another story.

Note also, that we decrease assignments to bs->file in code: it helps
us restrict modifying this field in further commit.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220726201134.924743-3-vsementsov@yandex-team.ru>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/block/crypto.c b/block/crypto.c
index 7a57774b76..396e529bb2 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -261,15 +261,14 @@ static int block_crypto_open_generic(QCryptoBlockFormat format,
 {
     BlockCrypto *crypto = bs->opaque;
     QemuOpts *opts = NULL;
-    int ret = -EINVAL;
+    int ret;
     QCryptoBlockOpenOptions *open_opts = NULL;
     unsigned int cflags = 0;
     QDict *cryptoopts = NULL;
 
-    bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
-                               BDRV_CHILD_IMAGE, false, errp);
-    if (!bs->file) {
-        return -EINVAL;
+    ret = bdrv_open_file_child(NULL, options, "file", bs, errp);
+    if (ret < 0) {
+        return ret;
     }
 
     bs->supported_write_flags = BDRV_REQ_FUA &
@@ -277,6 +276,7 @@ static int block_crypto_open_generic(QCryptoBlockFormat format,
 
     opts = qemu_opts_create(opts_spec, NULL, 0, &error_abort);
     if (!qemu_opts_absorb_qdict(opts, options, errp)) {
+        ret = -EINVAL;
         goto cleanup;
     }
 
@@ -285,6 +285,7 @@ static int block_crypto_open_generic(QCryptoBlockFormat format,
 
     open_opts = block_crypto_open_opts_init(cryptoopts, errp);
     if (!open_opts) {
+        ret = -EINVAL;
         goto cleanup;
     }