[Qemu-block] [PATCH v2] block/rbd: increase dynamically the image size

[Stefano Garzarella]

RBD APIs don't allow us to write more than the size set with
rbd_create() or rbd_resize().
In order to support growing images (eg. qcow2), we resize the
image before write operations that exceed the current size.

Signed-off-by: Stefano Garzarella <address@hidden>
---
v2:
  - use bs->total_sectors instead of adding a new field [Kevin]
  - resize the image only during write operation [Kevin]
    for read operation, the bdrv_aligned_preadv() already handles reads
    that exceed the length returned by bdrv_getlength(), so IMHO we can
    avoid to handle it in the rbd driver
---
 block/rbd.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/block/rbd.c b/block/rbd.c
index 0c549c9935..613e8f4982 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -934,13 +934,25 @@ static BlockAIOCB *rbd_start_aio(BlockDriverState *bs,
     }
 
     switch (cmd) {
-    case RBD_AIO_WRITE:
+    case RBD_AIO_WRITE: {
+        /*
+         * RBD APIs don't allow us to write more than actual size, so in order
+         * to support growing images, we resize the image before write
+         * operations that exceed the current size.
+         */
+        if (off + size > bs->total_sectors * BDRV_SECTOR_SIZE) {
+            r = rbd_resize(s->image, off + size);
+            if (r < 0) {
+                goto failed_completion;
+            }
+        }
 #ifdef LIBRBD_SUPPORTS_IOVEC
             r = rbd_aio_writev(s->image, qiov->iov, qiov->niov, off, c);
 #else
             r = rbd_aio_write(s->image, off, size, rcb->buf, c);
 #endif
         break;
+    }
     case RBD_AIO_READ:
 #ifdef LIBRBD_SUPPORTS_IOVEC
             r = rbd_aio_readv(s->image, qiov->iov, qiov->niov, off, c);
-- 
2.20.1