This flag signifies that a write request will not change the visible
disk content. With this flag set, it is sufficient to have the
BLK_PERM_WRITE_UNCHANGED permission instead of BLK_PERM_WRITE.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id:
20180421132929.21610-4-mreitz@redhat.com
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
assert(!waited || !req->serialising);
assert(req->overlap_offset <= offset);
assert(offset + bytes <= req->overlap_offset + req->overlap_bytes);
- assert(child->perm & BLK_PERM_WRITE);
+ if (flags & BDRV_REQ_WRITE_UNCHANGED) {
+ assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE));
+ } else {
+ assert(child->perm & BLK_PERM_WRITE);
+ }
assert(end_sector <= bs->total_sectors || child->perm & BLK_PERM_RESIZE);
ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req);
BDRV_REQ_FUA = 0x10,
BDRV_REQ_WRITE_COMPRESSED = 0x20,
+ /* Signifies that this write request will not change the visible disk
+ * content. */
+ BDRV_REQ_WRITE_UNCHANGED = 0x40,
+
/* Mask of valid flags */
- BDRV_REQ_MASK = 0x3f,
+ BDRV_REQ_MASK = 0x7f,
} BdrvRequestFlags;
typedef struct BlockSizes {