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>

1 files changed, 9 insertions, 1 deletions

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];