Re: [PATCH 1/2] block: introduce BLK_STS_OFFLINE

[Jens Axboe <axboe@kernel.dk>]

On 2/3/22 12:24 AM, Hannes Reinecke wrote:
> On 2/3/22 07:52, Song Liu wrote:
>> CC linux-block (it was a typo in the original email)
>>
>> On Wed, Feb 2, 2022 at 10:40 PM Song Liu <song@kernel.org> wrote:
>>>
>>> Currently, drivers reports BLK_STS_IOERR for devices that are not full
>>> online or being removed. This behavior could cause confusion for users,
>>> as they are not really I/O errors from the device.
>>>
>>> Solve this issue with a new state BLK_STS_OFFLINE, which reports "device
>>> offline error" in dmesg instead of "I/O error".
>>>
>>> Signed-off-by: Song Liu <song@kernel.org>
>>> ---
>>>   block/blk-core.c          | 1 +
>>>   include/linux/blk_types.h | 7 +++++++
>>>   2 files changed, 8 insertions(+)
>>>
>>> diff --git a/block/blk-core.c b/block/blk-core.c
>>> index 61f6a0dc4511..24035dd2eef1 100644
>>> --- a/block/blk-core.c
>>> +++ b/block/blk-core.c
>>> @@ -164,6 +164,7 @@ static const struct {
>>>          [BLK_STS_RESOURCE]      = { -ENOMEM,    "kernel resource" },
>>>          [BLK_STS_DEV_RESOURCE]  = { -EBUSY,     "device resource" },
>>>          [BLK_STS_AGAIN]         = { -EAGAIN,    "nonblocking retry" },
>>> +       [BLK_STS_OFFLINE]       = { -EIO,       "device offline" },
>>>
>>>          /* device mapper special case, should not leak out: */
>>>          [BLK_STS_DM_REQUEUE]    = { -EREMCHG, "dm internal retry" },
>>> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
>>> index fe065c394fff..5561e58d158a 100644
>>> --- a/include/linux/blk_types.h
>>> +++ b/include/linux/blk_types.h
>>> @@ -153,6 +153,13 @@ typedef u8 __bitwise blk_status_t;
>>>    */
>>>   #define BLK_STS_ZONE_ACTIVE_RESOURCE   ((__force blk_status_t)16)
>>>
>>> +/*
>>> + * BLK_STS_OFFLINE is returned from the driver when the target device is offline
>>> + * or is being taken offline. This could help differentiate the case where a
>>> + * device is intentionally being shut down from a real I/O error.
>>> + */
>>> +#define BLK_STS_OFFLINE                ((__force blk_status_t)17)
>>> +
>>>   /**
>>>    * blk_path_error - returns true if error may be path related
>>>    * @error: status the request was completed with
>>> --
>>> 2.30.2
>>>
> Please do not overload EIO here.
> EIO already is a catch-all error if we don't know any better, but for 
> the 'device offline' case we do (or rather should).
> Please map it onto 'ENODEV' or 'ENXIO'.

It's deliberately EIO as not to force a change in behavior. I don't mind
using something else, but that should be a separate change then.

-- 
Jens Axboe