block/get_block_status: avoid redundant callouts on raw devices

if a raw device like an iscsi target or host device is used
the current implementation makes a second call out to get
the block status of bs->file.

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -3147,6 +3147,12 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
         return ret;
     }
 
+    if (ret & BDRV_BLOCK_RAW) {
+        assert(ret & BDRV_BLOCK_OFFSET_VALID);
+        return bdrv_get_block_status(bs->file, ret >> BDRV_SECTOR_BITS,
+                                     *pnum, pnum);
+    }
+
     if (!(ret & BDRV_BLOCK_DATA)) {
         if (bdrv_has_zero_init(bs)) {
             ret |= BDRV_BLOCK_ZERO;

block/raw_bsd.c

@@ -62,7 +62,9 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
                                             int64_t sector_num,
                                             int nb_sectors, int *pnum)
 {
-    return bdrv_get_block_status(bs->file, sector_num, nb_sectors, pnum);
+    *pnum = nb_sectors;
+    return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | BDRV_BLOCK_DATA |
+           (sector_num << BDRV_SECTOR_BITS);
 }
 
 static int coroutine_fn raw_co_write_zeroes(BlockDriverState *bs,

include/block/block.h

@@ -84,6 +84,9 @@ typedef struct BlockDevOps {
 /* BDRV_BLOCK_DATA: data is read from bs->file or another file
  * BDRV_BLOCK_ZERO: sectors read as zero
  * BDRV_BLOCK_OFFSET_VALID: sector stored in bs->file as raw data
+ * BDRV_BLOCK_RAW: used internally to indicate that the request
+ *                 was answered by the raw driver and that one
+ *                 should look in bs->file directly.
  *
  * If BDRV_BLOCK_OFFSET_VALID is set, bits 9-62 represent the offset in
  * bs->file where sector data can be read from as raw data.
@@ -105,6 +108,7 @@ typedef struct BlockDevOps {
 #define BDRV_BLOCK_DATA         1
 #define BDRV_BLOCK_ZERO         2
 #define BDRV_BLOCK_OFFSET_VALID 4
+#define BDRV_BLOCK_RAW          8
 #define BDRV_BLOCK_OFFSET_MASK  BDRV_SECTOR_MASK
 
 typedef enum {