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Re: [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy on read |
Date: |
Fri, 7 Apr 2017 11:42:16 +0100 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
On Fri, Apr 07, 2017 at 12:32:45PM +0200, Kevin Wolf wrote:
> 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 <address@hidden>
> Signed-off-by: Kevin Wolf <address@hidden>
Thanks Kevin. As this is essentially the same as the patch I tested
last night,
Reviewed-by: Richard W.M. Jones <address@hidden>
Rich.
> block/io.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/block/io.c b/block/io.c
> index 2709a70..7321dda 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.
> --
> 1.8.3.1
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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