From 1bf03e66fd03af46ff0f98dd04b6e28f432ac1e3 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 7 Apr 2017 12:29:05 +0200 Subject: [PATCH] block: Don't check permissions for copy on read The assertion is currently failing. We can't require callers to have write permissions when all they are doing is a read, so comment it out. Add a FIXME comment in the code so that the check is re-enabled when copy on read is refactored into its own filter driver. Reported-by: Richard W.M. Jones Signed-off-by: Kevin Wolf Reviewed-by: Richard W.M. Jones --- block/io.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/block/io.c b/block/io.c index 2709a7007f..7321ddab3d 100644 --- a/block/io.c +++ b/block/io.c @@ -945,7 +945,14 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child, size_t skip_bytes; int ret; - assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE)); + /* FIXME We cannot require callers to have write permissions when all they + * are doing is a read request. If we did things right, write permissions + * would be obtained anyway, but internally by the copy-on-read code. As + * long as it is implemented here rather than in a separat filter driver, + * the copy-on-read code doesn't have its own BdrvChild, however, for which + * it could request permissions. Therefore we have to bypass the permission + * system for the moment. */ + // assert(child->perm & (BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE)); /* Cover entire cluster so no additional backing file I/O is required when * allocating cluster in the image file.