On 17.12.18 г. 9:49 ч., Anand Jain wrote:
>
>
> On 12/17/2018 02:55 PM, Nikolay Borisov wrote:
>>
>>
>> On 17.12.18 г. 5:13 ч., Anand Jain wrote:
>>> User space understands the ioctl BTRFS_IOC_DEV_REPLACE command status
>>> using the struct btrfs_ioctl_dev_replace_args::result, and so userspace
>>> initializes this to BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_RESULT, so exclude
>>> this value in checking for the error.
>>>
>>> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
>>> ---
>>> cmds-replace.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/cmds-replace.c b/cmds-replace.c
>>> index b30e6c781e64..42de4de8c031 100644
>>> --- a/cmds-replace.c
>>> +++ b/cmds-replace.c
>>> @@ -296,6 +296,8 @@ static int cmd_replace_start(int argc, char **argv)
>>> }
>>> if (start_args.result !=
>>> + BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_RESULT &&
>>> + start_args.result !=
>>
>> While this change is OK, it really is redundant, since we do
>> IOC_DEV_REPLACE with CMD_STATUS, meaning in kernel space we always call
>> btrfs_dev_replace_status which always overwrites ->result member.
>
>> Also looking at the other 3 cmds available for this IOCTL it's always
>> guaranteed for ->result to be overwritten if it executes btrfs code.
>
>> OTOH if the capable, memdup or an unrecognised ->cmd is detected then
>> an ordinary error code is returned, in which case the ret < 0 check
>> executes and laves via "leave_with_error" label.
>>
>> While your patch is OK code wise it's really a no op
>
> Did you miss the point that BTRFS_FS_EXCL_OP can be set by some other
> thread such as balance?.
> So in this context BTRFS_IOCTL_DEV_REPLACE_CMD_STATUS fails to> report BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS and as the replace thread
Then perhaps btrfs_dev_replace_status should be modified so that
->status is set to an appropriate value. Looking at it
replace_dev_result2string will also have to be extended to recognize
BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS.
> moves further ahead, the BTRFS_IOCTL_DEV_REPLACE_CMD_START will know
> that BTRFS_FS_EXCL_OP is set and the kernel does not reset the
> start_args.result value set by the user land which is
> BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_RESULT.
So what? the ioctl call will return BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS
which is positive (and you add handling for that in the second patch).
>
> Besides checking for BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_RESULT is a
> right thing in general.
What is the real problem you are trying to solve here?
>
>
>>> BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR) {
>>> error("ioctl(DEV_REPLACE_START) on '%s' returns error:
>>> %s",
>>> path,
>>>
