[Qemu-devel] [RFC PATCH v3 6/6] qcow2: Add full image preallocation option

[Hu Tao <hutao@cn.fujitsu.com>]

This adds a preallocation=full mode to qcow2 image creation, which
creates a non-sparse image file.

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
---
 block/qcow2.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 487a595..3c41d4a 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1386,7 +1386,7 @@ static int qcow2_change_backing_file(BlockDriverState *bs,
     return qcow2_update_header(bs);
 }
 
-static int preallocate(BlockDriverState *bs)
+static int preallocate(BlockDriverState *bs, enum prealloc_mode mode)
 {
     uint64_t nb_sectors;
     uint64_t offset;
@@ -1395,9 +1395,19 @@ static int preallocate(BlockDriverState *bs)
     int ret;
     QCowL2Meta *meta;
 
+    assert(mode != PREALLOC_OFF);
+
     nb_sectors = bdrv_getlength(bs) >> 9;
     offset = 0;
 
+    if (mode == PREALLOC_FULL) {
+        ret = bdrv_preallocate(bs->file, 0, bdrv_getlength(bs));
+        if (ret < 0) {
+            return ret;
+        }
+    }
+
+    /* allocate metadata */
     while (nb_sectors) {
         num = MIN(nb_sectors, INT_MAX >> 9);
         ret = qcow2_alloc_cluster_offset(bs, offset, 0, num, &num,
@@ -1577,11 +1587,11 @@ static int qcow2_create2(const char *filename, int64_t total_size,
         }
     }
 
-    /* And if we're supposed to preallocate metadata, do that now */
+    /* And if we're supposed to preallocate data, do that now */
     if (prealloc) {
         BDRVQcowState *s = bs->opaque;
         qemu_co_mutex_lock(&s->lock);
-        ret = preallocate(bs);
+        ret = preallocate(bs, prealloc);
         qemu_co_mutex_unlock(&s->lock);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Could not preallocate metadata");
@@ -1638,6 +1648,8 @@ static int qcow2_create(const char *filename, QEMUOptionParameter *options,
                 prealloc = PREALLOC_OFF;
             } else if (!strcmp(options->value.s, "metadata")) {
                 prealloc = PREALLOC_METADATA;
+            } else if (!strcmp(options->value.s, "full")) {
+                prealloc = PREALLOC_FULL;
             } else {
                 error_setg(errp, "Invalid preallocation mode: '%s'",
                            options->value.s);
@@ -2229,7 +2241,7 @@ static QEMUOptionParameter qcow2_create_options[] = {
     {
         .name = BLOCK_OPT_PREALLOC,
         .type = OPT_STRING,
-        .help = "Preallocation mode (allowed values: off, metadata)"
+        .help = "Preallocation mode (allowed values: off, metadata, full)"
     },
     {
         .name = BLOCK_OPT_LAZY_REFCOUNTS,
-- 
1.7.11.7