[v7,01/10] block: Add flags to BlockDriver.bdrv_co_truncate()

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 4c3587ea19..92335f33c7 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -355,7 +355,7 @@  struct BlockDriver {
      */
     int coroutine_fn (*bdrv_co_truncate)(BlockDriverState *bs, int64_t offset,
                                          bool exact, PreallocMode prealloc,
-                                         Error **errp);
+                                         BdrvRequestFlags flags, Error **errp);
 
     int64_t (*bdrv_getlength)(BlockDriverState *bs);
     bool has_variable_length;
@@ -847,6 +847,14 @@  struct BlockDriverState {
     /* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
      * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED) */
     unsigned int supported_zero_flags;
+    /*
+     * Flags honoured during truncate (so far: BDRV_REQ_ZERO_WRITE).
+     *
+     * If BDRV_REQ_ZERO_WRITE is given, the truncate operation must make sure
+     * that any added space reads as all zeros. If this can't be guaranteed,
+     * the operation must fail.
+     */
+    unsigned int supported_truncate_flags;
 
     /* the following member gives a name to every node on the bs graph. */
     char node_name[32];
diff --git a/block/crypto.c b/block/crypto.c
index d577f89659..3721a8495c 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -299,7 +299,8 @@  static int block_crypto_co_create_generic(BlockDriverState *bs,
 
 static int coroutine_fn
 block_crypto_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
-                         PreallocMode prealloc, Error **errp)
+                         PreallocMode prealloc, BdrvRequestFlags flags,
+                         Error **errp)
 {
     BlockCrypto *crypto = bs->opaque;
     uint64_t payload_offset =
diff --git a/block/file-posix.c b/block/file-posix.c
index 7e19bbff5f..53f475ed61 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2080,7 +2080,7 @@  raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,
 
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
-                                        Error **errp)
+                                        BdrvRequestFlags flags, Error **errp)
 {
     BDRVRawState *s = bs->opaque;
     struct stat st;
diff --git a/block/file-win32.c b/block/file-win32.c
index 15859839a1..a6b0dda5c3 100644
--- a/block/file-win32.c
+++ b/block/file-win32.c
@@ -469,7 +469,7 @@  static void raw_close(BlockDriverState *bs)
 
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
-                                        Error **errp)
+                                        BdrvRequestFlags flags, Error **errp)
 {
     BDRVRawState *s = bs->opaque;
     LONG low, high;
diff --git a/block/gluster.c b/block/gluster.c
index 0aa1f2cda4..d06df900f6 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1228,6 +1228,7 @@  static coroutine_fn int qemu_gluster_co_truncate(BlockDriverState *bs,
                                                  int64_t offset,
                                                  bool exact,
                                                  PreallocMode prealloc,
+                                                 BdrvRequestFlags flags,
                                                  Error **errp)
 {
     BDRVGlusterState *s = bs->opaque;
diff --git a/block/io.c b/block/io.c
index aba67f66b9..04ac5cf023 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3344,6 +3344,7 @@  int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
     BlockDriverState *bs = child->bs;
     BlockDriver *drv = bs->drv;
     BdrvTrackedRequest req;
+    BdrvRequestFlags flags = 0;
     int64_t old_size, new_bytes;
     int ret;
 
@@ -3394,7 +3395,12 @@  int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
     }
 
     if (drv->bdrv_co_truncate) {
-        ret = drv->bdrv_co_truncate(bs, offset, exact, prealloc, errp);
+        if (flags & ~bs->supported_truncate_flags) {
+            error_setg(errp, "Block driver does not support requested flags");
+            ret = -ENOTSUP;
+            goto out;
+        }
+        ret = drv->bdrv_co_truncate(bs, offset, exact, prealloc, flags, errp);
     } else if (bs->file && drv->is_filter) {
         ret = bdrv_co_truncate(bs->file, offset, exact, prealloc, errp);
     } else {
diff --git a/block/iscsi.c b/block/iscsi.c
index 0b4b7210df..914a1de9fb 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -2124,7 +2124,7 @@  static void iscsi_reopen_commit(BDRVReopenState *reopen_state)
 
 static int coroutine_fn iscsi_co_truncate(BlockDriverState *bs, int64_t offset,
                                           bool exact, PreallocMode prealloc,
-                                          Error **errp)
+                                          BdrvRequestFlags flags, Error **errp)
 {
     IscsiLun *iscsilun = bs->opaque;
     int64_t cur_length;
diff --git a/block/nfs.c b/block/nfs.c
index cc2413d5ab..2393fbfe6b 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -755,7 +755,8 @@  static int64_t nfs_get_allocated_file_size(BlockDriverState *bs)
 
 static int coroutine_fn
 nfs_file_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
-                     PreallocMode prealloc, Error **errp)
+                     PreallocMode prealloc, BdrvRequestFlags flags,
+                     Error **errp)
 {
     NFSClient *client = bs->opaque;
     int ret;
diff --git a/block/qcow2.c b/block/qcow2.c
index b524b0c53f..0b406b22fb 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3964,7 +3964,7 @@  fail:
 
 static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
                                           bool exact, PreallocMode prealloc,
-                                          Error **errp)
+                                          BdrvRequestFlags flags, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     uint64_t old_length;
diff --git a/block/qed.c b/block/qed.c
index 1af9b3cb1d..fb6100bd20 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -1467,6 +1467,7 @@  static int coroutine_fn bdrv_qed_co_truncate(BlockDriverState *bs,
                                              int64_t offset,
                                              bool exact,
                                              PreallocMode prealloc,
+                                             BdrvRequestFlags flags,
                                              Error **errp)
 {
     BDRVQEDState *s = bs->opaque;
diff --git a/block/raw-format.c b/block/raw-format.c
index 93b25e1b6b..9331368f43 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -371,7 +371,7 @@  static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
 
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
-                                        Error **errp)
+                                        BdrvRequestFlags flags, Error **errp)
 {
     BDRVRawState *s = bs->opaque;
 
diff --git a/block/rbd.c b/block/rbd.c
index e637639a07..f2d52091c7 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -1108,6 +1108,7 @@  static int coroutine_fn qemu_rbd_co_truncate(BlockDriverState *bs,
                                              int64_t offset,
                                              bool exact,
                                              PreallocMode prealloc,
+                                             BdrvRequestFlags flags,
                                              Error **errp)
 {
     int r;
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 59f7ebb171..ef0a6e743e 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2288,7 +2288,7 @@  static int64_t sd_getlength(BlockDriverState *bs)
 
 static int coroutine_fn sd_co_truncate(BlockDriverState *bs, int64_t offset,
                                        bool exact, PreallocMode prealloc,
-                                       Error **errp)
+                                       BdrvRequestFlags flags, Error **errp)
 {
     BDRVSheepdogState *s = bs->opaque;
     int ret, fd;
@@ -2604,7 +2604,7 @@  static coroutine_fn int sd_co_writev(BlockDriverState *bs, int64_t sector_num,
 
     assert(!flags);
     if (offset > s->inode.vdi_size) {
-        ret = sd_co_truncate(bs, offset, false, PREALLOC_MODE_OFF, NULL);
+        ret = sd_co_truncate(bs, offset, false, PREALLOC_MODE_OFF, 0, NULL);
         if (ret < 0) {
             return ret;
         }
diff --git a/block/ssh.c b/block/ssh.c
index 84e92821c0..9eb33df859 100644
--- a/block/ssh.c
+++ b/block/ssh.c
@@ -1298,7 +1298,7 @@  static int64_t ssh_getlength(BlockDriverState *bs)
 
 static int coroutine_fn ssh_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
-                                        Error **errp)
+                                        BdrvRequestFlags flags, Error **errp)
 {
     BDRVSSHState *s = bs->opaque;
 
diff --git a/tests/test-block-iothread.c b/tests/test-block-iothread.c
index 0c861809f0..2f3b76323d 100644
--- a/tests/test-block-iothread.c
+++ b/tests/test-block-iothread.c
@@ -46,7 +46,8 @@  static int coroutine_fn bdrv_test_co_pdiscard(BlockDriverState *bs,
 
 static int coroutine_fn
 bdrv_test_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
-                      PreallocMode prealloc, Error **errp)
+                      PreallocMode prealloc, BdrvRequestFlags flags,
+                      Error **errp)
 {
     return 0;
 }