* [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy on read
@ 2017-04-07 10:32 Kevin Wolf
2017-04-07 10:42 ` Richard W.M. Jones
2017-04-07 13:53 ` Eric Blake
0 siblings, 2 replies; 4+ messages in thread
From: Kevin Wolf @ 2017-04-07 10:32 UTC (permalink / raw)
To: qemu-block; +Cc: kwolf, mreitz, eblake, rjones, qemu-devel
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 <rjones@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy on read
2017-04-07 10:32 [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy on read Kevin Wolf
@ 2017-04-07 10:42 ` Richard W.M. Jones
2017-04-07 13:53 ` Eric Blake
1 sibling, 0 replies; 4+ messages in thread
From: Richard W.M. Jones @ 2017-04-07 10:42 UTC (permalink / raw)
To: Kevin Wolf; +Cc: qemu-block, mreitz, eblake, qemu-devel
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 <rjones@redhat.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Thanks Kevin. As this is essentially the same as the patch I tested
last night,
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
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
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy on read
2017-04-07 10:32 [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy on read Kevin Wolf
2017-04-07 10:42 ` Richard W.M. Jones
@ 2017-04-07 13:53 ` Eric Blake
2017-04-07 14:01 ` Max Reitz
1 sibling, 1 reply; 4+ messages in thread
From: Eric Blake @ 2017-04-07 13:53 UTC (permalink / raw)
To: Kevin Wolf, qemu-block; +Cc: mreitz, rjones, qemu-devel
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On 04/07/2017 05:32 AM, 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 <rjones@redhat.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
> 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,
s/separat/separate/
> + * 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));
Makes checkpatch.pl unhappy - but that's intentional.
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy on read
2017-04-07 13:53 ` Eric Blake
@ 2017-04-07 14:01 ` Max Reitz
0 siblings, 0 replies; 4+ messages in thread
From: Max Reitz @ 2017-04-07 14:01 UTC (permalink / raw)
To: Eric Blake, Kevin Wolf, qemu-block; +Cc: rjones, qemu-devel
[-- Attachment #1: Type: text/plain, Size: 1782 bytes --]
On 07.04.2017 15:53, Eric Blake wrote:
> On 04/07/2017 05:32 AM, 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 <rjones@redhat.com>
>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>> ---
>> 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,
>
> s/separat/separate/
>
>> + * 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));
>
> Makes checkpatch.pl unhappy - but that's intentional.
Is it? I don't know. But not that I mind, so for good measure:
Reviewed-by: Max Reitz <mreitz@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
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^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-04-07 10:32 [Qemu-devel] [PATCH for-2.9] block: Don't check permissions for copy on read Kevin Wolf
2017-04-07 10:42 ` Richard W.M. Jones
2017-04-07 13:53 ` Eric Blake
2017-04-07 14:01 ` Max Reitz
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