Implement the preallocation modes falloc and full for growing qcow2
images.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/qcow2.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 80fb815b15..b6b08d70da 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2604,7 +2604,9 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
     int64_t new_l1_size;
     int ret;
 
-    if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA) {
+    if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA &&
+        prealloc != PREALLOC_MODE_FALLOC && prealloc != PREALLOC_MODE_FULL)
+    {
         error_setg(errp, "Unsupported preallocation mode '%s'",
                    PreallocMode_lookup[prealloc]);
         return -ENOTSUP;
@@ -2649,6 +2651,38 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
         }
         break;
 
+    case PREALLOC_MODE_FALLOC:
+    case PREALLOC_MODE_FULL:
+    {
+        uint64_t additional_size = qcow2_calc_size_usage(bs, old_length, offset,
+                                                         s->cluster_bits,
+                                                         s->refcount_order);
+        int64_t old_file_length = bdrv_getlength(bs->file->bs);
+        if (old_file_length < 0) {
+            error_setg(errp, "Failed to inquire file length");
+            return old_file_length;
+        }
+
+        old_file_length = ROUND_UP(old_file_length, s->cluster_size);
+
+        ret = bdrv_truncate(bs->file, old_file_length + additional_size,
+                            prealloc, errp);
+        if (ret < 0) {
+            error_prepend(errp, "Failed to resize underlying file");
+            return ret;
+        }
+
+        /* Ensure that preallocation is done in the preallocated area */
+        s->free_cluster_index = old_file_length / s->cluster_size;
+        ret = preallocate(bs, old_length, offset);
+        if (ret < 0) {
+            error_setg_errno(errp, -ret, "Preallocation failed, image may now "
+                             "occupy more space than necessary");
+            return ret;
+        }
+        break;
+    }
+
     default:
         g_assert_not_reached();
     }
-- 
2.12.0

On Mon, Mar 13, 2017 at 10:41:15PM +0100, Max Reitz wrote:
> Implement the preallocation modes falloc and full for growing qcow2
> images.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2.c | 36 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 80fb815b15..b6b08d70da 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2604,7 +2604,9 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
>      int64_t new_l1_size;
>      int ret;
>  
> -    if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA) {
> +    if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA &&
> +        prealloc != PREALLOC_MODE_FALLOC && prealloc != PREALLOC_MODE_FULL)

Now all cases are covered so this if statement can be dropped.  If you
are worried about new preallocation modes being added in the future then
the error_setg() can be moved into the switch statement's default case.

On 20.03.2017 12:29, Stefan Hajnoczi wrote:
> On Mon, Mar 13, 2017 at 10:41:15PM +0100, Max Reitz wrote:
>> Implement the preallocation modes falloc and full for growing qcow2
>> images.
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>  block/qcow2.c | 36 +++++++++++++++++++++++++++++++++++-
>>  1 file changed, 35 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/qcow2.c b/block/qcow2.c
>> index 80fb815b15..b6b08d70da 100644
>> --- a/block/qcow2.c
>> +++ b/block/qcow2.c
>> @@ -2604,7 +2604,9 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
>>      int64_t new_l1_size;
>>      int ret;
>>  
>> -    if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA) {
>> +    if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA &&
>> +        prealloc != PREALLOC_MODE_FALLOC && prealloc != PREALLOC_MODE_FULL)
> 
> Now all cases are covered so this if statement can be dropped.  If you
> are worried about new preallocation modes being added in the future then
> the error_setg() can be moved into the switch statement's default case.

No, because the switch comes after we have already grown the L1 table.
That wouldn't be so nice.

Max

On Mon, Mar 20, 2017 at 04:15:59PM +0100, Max Reitz wrote:
> On 20.03.2017 12:29, Stefan Hajnoczi wrote:
> > On Mon, Mar 13, 2017 at 10:41:15PM +0100, Max Reitz wrote:
> >> Implement the preallocation modes falloc and full for growing qcow2
> >> images.
> >>
> >> Signed-off-by: Max Reitz <mreitz@redhat.com>
> >> ---
> >>  block/qcow2.c | 36 +++++++++++++++++++++++++++++++++++-
> >>  1 file changed, 35 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/block/qcow2.c b/block/qcow2.c
> >> index 80fb815b15..b6b08d70da 100644
> >> --- a/block/qcow2.c
> >> +++ b/block/qcow2.c
> >> @@ -2604,7 +2604,9 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
> >>      int64_t new_l1_size;
> >>      int ret;
> >>  
> >> -    if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA) {
> >> +    if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA &&
> >> +        prealloc != PREALLOC_MODE_FALLOC && prealloc != PREALLOC_MODE_FULL)
> > 
> > Now all cases are covered so this if statement can be dropped.  If you
> > are worried about new preallocation modes being added in the future then
> > the error_setg() can be moved into the switch statement's default case.
> 
> No, because the switch comes after we have already grown the L1 table.
> That wouldn't be so nice.

Oops :)

Stefan