qcow2: Basic definitions for external data files

This adds basic constants, struct fields and helper function for
external data file support to the implementation.

QCOW2_INCOMPAT_MASK and QCOW2_AUTOCLEAR_MASK are not updated yet so that
opening images with an external data file still fails (we don't handle
them correctly yet).
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qcow2.c

@@ -73,6 +73,7 @@ typedef struct {
 #define  QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857
 #define  QCOW2_EXT_MAGIC_CRYPTO_HEADER 0x0537be77
 #define  QCOW2_EXT_MAGIC_BITMAPS 0x23852875
+#define  QCOW2_EXT_MAGIC_DATA_FILE 0x44415441
 
 static int coroutine_fn
 qcow2_co_preadv_compressed(BlockDriverState *bs,
@@ -1452,6 +1453,9 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
         goto fail;
     }
 
+    /* TODO Open external data file */
+    s->data_file = bs->file;
+
     /* qcow2_read_extension may have set up the crypto context
      * if the crypt method needs a header region, some methods
      * don't need header extensions, so must check here
@@ -2440,6 +2444,11 @@ int qcow2_update_header(BlockDriverState *bs)
                 .bit  = QCOW2_INCOMPAT_CORRUPT_BITNR,
                 .name = "corrupt bit",
             },
+            {
+                .type = QCOW2_FEAT_TYPE_INCOMPATIBLE,
+                .bit  = QCOW2_INCOMPAT_DATA_FILE_BITNR,
+                .name = "external data file",
+            },
             {
                 .type = QCOW2_FEAT_TYPE_COMPATIBLE,
                 .bit  = QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR,

block/qcow2.h

@@ -197,13 +197,15 @@ enum {
 
 /* Incompatible feature bits */
 enum {
-    QCOW2_INCOMPAT_DIRTY_BITNR   = 0,
-    QCOW2_INCOMPAT_CORRUPT_BITNR = 1,
-    QCOW2_INCOMPAT_DIRTY         = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
-    QCOW2_INCOMPAT_CORRUPT       = 1 << QCOW2_INCOMPAT_CORRUPT_BITNR,
-
-    QCOW2_INCOMPAT_MASK          = QCOW2_INCOMPAT_DIRTY
-                                 | QCOW2_INCOMPAT_CORRUPT,
+    QCOW2_INCOMPAT_DIRTY_BITNR      = 0,
+    QCOW2_INCOMPAT_CORRUPT_BITNR    = 1,
+    QCOW2_INCOMPAT_DATA_FILE_BITNR  = 2,
+    QCOW2_INCOMPAT_DIRTY            = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
+    QCOW2_INCOMPAT_CORRUPT          = 1 << QCOW2_INCOMPAT_CORRUPT_BITNR,
+    QCOW2_INCOMPAT_DATA_FILE        = 1 << QCOW2_INCOMPAT_DATA_FILE_BITNR,
+
+    QCOW2_INCOMPAT_MASK             = QCOW2_INCOMPAT_DIRTY
+                                    | QCOW2_INCOMPAT_CORRUPT,
 };
 
 /* Compatible feature bits */
@@ -216,10 +218,12 @@ enum {
 
 /* Autoclear feature bits */
 enum {
-    QCOW2_AUTOCLEAR_BITMAPS_BITNR = 0,
-    QCOW2_AUTOCLEAR_BITMAPS       = 1 << QCOW2_AUTOCLEAR_BITMAPS_BITNR,
+    QCOW2_AUTOCLEAR_BITMAPS_BITNR       = 0,
+    QCOW2_AUTOCLEAR_DATA_FILE_RAW_BITNR = 1,
+    QCOW2_AUTOCLEAR_BITMAPS             = 1 << QCOW2_AUTOCLEAR_BITMAPS_BITNR,
+    QCOW2_AUTOCLEAR_DATA_FILE_RAW       = 1 << QCOW2_AUTOCLEAR_DATA_FILE_RAW_BITNR,
 
-    QCOW2_AUTOCLEAR_MASK          = QCOW2_AUTOCLEAR_BITMAPS,
+    QCOW2_AUTOCLEAR_MASK                = QCOW2_AUTOCLEAR_BITMAPS,
 };
 
 enum qcow2_discard_type {
@@ -340,6 +344,8 @@ typedef struct BDRVQcow2State {
 
     CoQueue compress_wait_queue;
     int nb_compress_threads;
+
+    BdrvChild *data_file;
 } BDRVQcow2State;
 
 typedef struct Qcow2COWRegion {
@@ -457,6 +463,12 @@ typedef enum QCow2MetadataOverlap {
 
 #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
 
+static inline bool has_data_file(BlockDriverState *bs)
+{
+    BDRVQcow2State *s = bs->opaque;
+    return (s->data_file != bs->file);
+}
+
 static inline int64_t start_of_cluster(BDRVQcow2State *s, int64_t offset)
 {
     return offset & ~(s->cluster_size - 1);

tests/qemu-iotests/031.out

@@ -117,7 +117,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 Header extension:
@@ -150,7 +150,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 Header extension:
@@ -164,7 +164,7 @@ No errors were found on the image.
 
 magic                     0x514649fb
 version                   3
-backing_file_offset       0x148
+backing_file_offset       0x178
 backing_file_size         0x17
 cluster_bits              16
 size                      67108864
@@ -188,7 +188,7 @@ data                      'host_device'
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 Header extension:

tests/qemu-iotests/036.out

@@ -58,7 +58,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 
@@ -86,7 +86,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 *** done

tests/qemu-iotests/061.out

@@ -26,7 +26,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 magic                     0x514649fb
@@ -84,7 +84,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 magic                     0x514649fb
@@ -144,7 +144,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 ERROR cluster 5 refcount=0 reference=1
@@ -199,7 +199,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 magic                     0x514649fb
@@ -268,7 +268,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 read 65536/65536 bytes at offset 44040192
@@ -306,7 +306,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 ERROR cluster 5 refcount=0 reference=1
@@ -335,7 +335,7 @@ header_length             104
 
 Header extension:
 magic                     0x6803f857
-length                    144
+length                    192
 data                      <binary>
 
 read 131072/131072 bytes at offset 0