[Qemu-devel] [PATCH v3] LUKS: support preallocation

[Maxim Levitsky <mlevitsk@redhat.com>]

preallocation=off and preallocation=metadata
both allocate luks header only, and preallocation=falloc/full
is passed to underlying file.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1534951

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>

---

Note that QMP support was only compile tested, since I am still learning
on how to use it.

If there is some library/script/etc which makes it more high level,
I would more that glad to hear about it. So far I used the qmp-shell

Also can I use qmp's blockdev-create outside a vm running?

 block/crypto.c       | 29 ++++++++++++++++++++++++++---
 qapi/block-core.json |  5 ++++-
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/block/crypto.c b/block/crypto.c
index 8237424ae6..034a645652 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -74,6 +74,7 @@ static ssize_t block_crypto_read_func(QCryptoBlock *block,
 struct BlockCryptoCreateData {
     BlockBackend *blk;
     uint64_t size;
+    PreallocMode prealloc;
 };
 
 
@@ -112,7 +113,7 @@ static ssize_t block_crypto_init_func(QCryptoBlock *block,
      * available to the guest, so we must take account of that
      * which will be used by the crypto header
      */
-    return blk_truncate(data->blk, data->size + headerlen, PREALLOC_MODE_OFF,
+    return blk_truncate(data->blk, data->size + headerlen, data->prealloc,
                         errp);
 }
 
@@ -251,6 +252,7 @@ static int block_crypto_open_generic(QCryptoBlockFormat format,
 static int block_crypto_co_create_generic(BlockDriverState *bs,
                                           int64_t size,
                                           QCryptoBlockCreateOptions *opts,
+                                          PreallocMode prealloc,
                                           Error **errp)
 {
     int ret;
@@ -266,9 +268,14 @@ static int block_crypto_co_create_generic(BlockDriverState *bs,
         goto cleanup;
     }
 
+    if (prealloc == PREALLOC_MODE_METADATA) {
+        prealloc = PREALLOC_MODE_OFF;
+    }
+
     data = (struct BlockCryptoCreateData) {
         .blk = blk,
         .size = size,
+        .prealloc = prealloc,
     };
 
     crypto = qcrypto_block_create(opts, NULL,
@@ -500,6 +507,7 @@ block_crypto_co_create_luks(BlockdevCreateOptions *create_options, Error **errp)
     BlockdevCreateOptionsLUKS *luks_opts;
     BlockDriverState *bs = NULL;
     QCryptoBlockCreateOptions create_opts;
+    PreallocMode preallocation = PREALLOC_MODE_OFF;
     int ret;
 
     assert(create_options->driver == BLOCKDEV_DRIVER_LUKS);
@@ -515,8 +523,11 @@ block_crypto_co_create_luks(BlockdevCreateOptions *create_options, Error **errp)
         .u.luks = *qapi_BlockdevCreateOptionsLUKS_base(luks_opts),
     };
 
+    if (luks_opts->has_preallocation)
+        preallocation = luks_opts->preallocation;
+
     ret = block_crypto_co_create_generic(bs, luks_opts->size, &create_opts,
-                                         errp);
+                                         preallocation, errp);
     if (ret < 0) {
         goto fail;
     }
@@ -534,12 +545,24 @@ static int coroutine_fn block_crypto_co_create_opts_luks(const char *filename,
     QCryptoBlockCreateOptions *create_opts = NULL;
     BlockDriverState *bs = NULL;
     QDict *cryptoopts;
+    PreallocMode prealloc;
+    char *buf = NULL;
     int64_t size;
     int ret;
+    Error *local_err = NULL;
 
     /* Parse options */
     size = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0);
 
+    buf = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
+    prealloc = qapi_enum_parse(&PreallocMode_lookup, buf,
+                               PREALLOC_MODE_OFF, &local_err);
+    g_free(buf);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return -EINVAL;
+    }
+
     cryptoopts = qemu_opts_to_qdict_filtered(opts, NULL,
                                              &block_crypto_create_opts_luks,
                                              true);
@@ -565,7 +588,7 @@ static int coroutine_fn block_crypto_co_create_opts_luks(const char *filename,
     }
 
     /* Create format layer */
-    ret = block_crypto_co_create_generic(bs, size, create_opts, errp);
+    ret = block_crypto_co_create_generic(bs, size, create_opts, prealloc, errp);
     if (ret < 0) {
         goto fail;
     }
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 0d43d4f37c..ebcfc9f903 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4205,13 +4205,16 @@
 #
 # @file             Node to create the image format on
 # @size             Size of the virtual disk in bytes
+# @preallocation    Preallocation mode for the new image (default: off;
+#                   allowed values: off/falloc/full
 #
 # Since: 2.12
 ##
 { 'struct': 'BlockdevCreateOptionsLUKS',
   'base': 'QCryptoBlockCreateOptionsLUKS',
   'data': { 'file':             'BlockdevRef',
-            'size':             'size' } }
+            'size':             'size',
+            '*preallocation':   'PreallocMode' } }
 
 ##
 # @BlockdevCreateOptionsNfs:
-- 
2.17.2