[Qemu-devel] [RFC PATCH 07/10] qcow2: Handle full/falloc preallocation in qcow2_create2()

Kevin Wolf posted 10 patches 8 years ago
[Qemu-devel] [RFC PATCH 07/10] qcow2: Handle full/falloc preallocation in qcow2_create2()
Posted by Kevin Wolf 8 years ago
Once qcow2_create2() can be called directly on an already existing node,
we must provide the 'full' and 'falloc' preallocation modes outside of
creating the image on the protocol layer. Fortunately, we have
preallocated truncate now which can provide this functionality.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2.c | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 686b765c06..868e0e8a62 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2832,6 +2832,25 @@ static int qcow2_create2(BlockdevCreateOptions *create_options, Error **errp)
     }
     blk_set_allow_write_beyond_eof(blk, true);
 
+    /* Clear the protocol layer and preallocate it if necessary */
+    ret = blk_truncate(blk, 0, PREALLOC_MODE_OFF, errp);
+    if (ret < 0) {
+        goto out;
+    }
+
+    if (qcow2_opts->preallocation == PREALLOC_MODE_FULL ||
+        qcow2_opts->preallocation == PREALLOC_MODE_FALLOC)
+    {
+        int64_t prealloc_size =
+            qcow2_calc_prealloc_size(qcow2_opts->size, cluster_size,
+                                     refcount_order);
+
+        ret = blk_truncate(blk, prealloc_size, qcow2_opts->preallocation, errp);
+        if (ret < 0) {
+            goto out;
+        }
+    }
+
     /* Write the header */
     QEMU_BUILD_BUG_ON((1 << MIN_CLUSTER_BITS) < sizeof(*header));
     header = g_malloc0(cluster_size);
@@ -3068,15 +3087,6 @@ static int qcow2_create(const char *filename, QemuOpts *opts, Error **errp)
 
 
     /* Create and open the file (protocol layer */
-    if (prealloc == PREALLOC_MODE_FULL || prealloc == PREALLOC_MODE_FALLOC) {
-        int refcount_order = ctz32(refcount_bits);
-        int64_t prealloc_size =
-            qcow2_calc_prealloc_size(size, cluster_size, refcount_order);
-        qemu_opt_set_number(opts, BLOCK_OPT_SIZE, prealloc_size, &error_abort);
-        qemu_opt_set(opts, BLOCK_OPT_PREALLOC, PreallocMode_str(prealloc),
-                     &error_abort);
-    }
-
     ret = bdrv_create_file(filename, opts, errp);
     if (ret < 0) {
         goto finish;
-- 
2.13.6


Re: [Qemu-devel] [RFC PATCH 07/10] qcow2: Handle full/falloc preallocation in qcow2_create2()
Posted by Eric Blake 8 years ago
On 01/11/2018 01:52 PM, Kevin Wolf wrote:
> Once qcow2_create2() can be called directly on an already existing node,
> we must provide the 'full' and 'falloc' preallocation modes outside of
> creating the image on the protocol layer. Fortunately, we have
> preallocated truncate now which can provide this functionality.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qcow2.c | 28 +++++++++++++++++++---------
>  1 file changed, 19 insertions(+), 9 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org