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block/qcow2: Metadata preallocation for truncate 

We can support PREALLOC_MODE_METADATA by invoking preallocate() in
qcow2_truncate().

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170613202107.10125-12-mreitz@redhat.com
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2017-06-13 22:21:02 +02:00
parent 652fecd005
commit 95b98f343b
1 changed files with 31 additions and 2 deletions
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33
block/qcow2.c
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@ -3077,10 +3077,11 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
PreallocMode prealloc, Error **errp)
{
BDRVQcow2State *s = bs->opaque;
uint64_t old_length;
int64_t new_l1_size;
int ret;
if (prealloc != PREALLOC_MODE_OFF) {
if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA) {
error_setg(errp, "Unsupported preallocation mode '%s'",
PreallocMode_lookup[prealloc]);
return -ENOTSUP;
@ -3104,8 +3105,10 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
return -ENOTSUP;
}
old_length = bs->total_sectors * 512;
/* shrinking is currently not supported */
if (offset < bs->total_sectors * 512) {
if (offset < old_length) {
error_setg(errp, "qcow2 doesn't support shrinking images yet");
return -ENOTSUP;
}
@ -3117,6 +3120,32 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
return ret;
}
switch (prealloc) {
case PREALLOC_MODE_OFF:
break;
case PREALLOC_MODE_METADATA:
ret = preallocate(bs, old_length, offset);
if (ret < 0) {
error_setg_errno(errp, -ret, "Preallocation failed");
return ret;
}
break;
default:
g_assert_not_reached();
}
if (prealloc != PREALLOC_MODE_OFF) {
/* Flush metadata before actually changing the image size */
ret = bdrv_flush(bs);
if (ret < 0) {
error_setg_errno(errp, -ret,
"Failed to flush the preallocated area to disk");
return ret;
}
}
/* write updated header.size */
offset = cpu_to_be64(offset);
ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, size),