From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53858) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cxx8c-0008Rh-RE for qemu-devel@nongnu.org; Tue, 11 Apr 2017 10:51:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cxx8c-0007jr-2g for qemu-devel@nongnu.org; Tue, 11 Apr 2017 10:51:22 -0400 From: Max Reitz Date: Tue, 11 Apr 2017 16:50:50 +0200 Message-Id: <20170411145050.31290-1-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH for-2.9?] block/io: Comment out permission assertions List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Max Reitz , Kevin Wolf , Laurent Vivier , Stefan Hajnoczi , Fam Zheng In case of block migration, there may be writes to BlockBackends that do not have the write permission taken. Before this issue is fixed (which is not going to happen in 2.9), we therefore cannot assert that this is the case. Suggested-by: Kevin Wolf Signed-off-by: Max Reitz --- block.c | 6 +++++- block/io.c | 12 ++++++++++-- 2 files changed, 15 insertions(+), 3 deletions(-) diff --git a/block.c b/block.c index 086a12df97..1fbbb8d606 100644 --- a/block.c +++ b/block.c @@ -3274,7 +3274,11 @@ int bdrv_truncate(BdrvChild *child, int64_t offset) BlockDriver *drv = bs->drv; int ret; - assert(child->perm & BLK_PERM_RESIZE); + /* FIXME: Some format block drivers use this function instead of implicitly + * growing their file by writing beyond its end. + * See bdrv_aligned_pwritev() for an explanation why we currently + * cannot assert this permission in that case. */ + // assert(child->perm & BLK_PERM_RESIZE); if (!drv) return -ENOMEDIUM; diff --git a/block/io.c b/block/io.c index bae6947032..8706bfa578 100644 --- a/block/io.c +++ b/block/io.c @@ -1345,8 +1345,16 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child, assert(!waited || !req->serialising); assert(req->overlap_offset <= offset); assert(offset + bytes <= req->overlap_offset + req->overlap_bytes); - assert(child->perm & BLK_PERM_WRITE); - assert(end_sector <= bs->total_sectors || child->perm & BLK_PERM_RESIZE); + /* FIXME: Block migration uses the BlockBackend of the guest device at a + * point when it has not yet taken write permissions. This will be + * fixed by a future patch, but for now we have to bypass this + * assertion for block migration to work. */ + // assert(child->perm & BLK_PERM_WRITE); + /* FIXME: Because of the above, we also cannot guarantee that all format + * BDS take the BLK_PERM_RESIZE permission on their file BDS, since + * they are not obligated to do so if they do not have any parent + * that has taken the permission to write to them. */ + // assert(end_sector <= bs->total_sectors || child->perm & BLK_PERM_RESIZE); ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req); -- 2.12.2