block: Add flags to BlockDriver.bdrv_co_truncate()

This adds a new BdrvRequestFlags parameter to the .bdrv_co_truncate()
driver callbacks, and a supported_truncate_flags field in
BlockDriverState that allows drivers to advertise support for request
flags in the context of truncate.

For now, we always pass 0 and no drivers declare support for any flag.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200424125448.63318-2-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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 =

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;

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;

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;

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 {

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;

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;

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;

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;

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;
 

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;

block/sheepdog.c

@@ -2281,7 +2281,7 @@ 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;
@@ -2597,7 +2597,7 @@ 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;
         }

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;
 

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];

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;
 }