Re: [PATCH] block: don't do revalidate zones on invalid devices

[Johannes Thumshirn <Johannes.Thumshirn@wdc.com>]

On 01/08/2020 00:33, Jens Axboe wrote:
> On 7/31/20 1:43 AM, Johannes Thumshirn wrote:
>> On 30/07/2020 14:33, Damien Le Moal wrote:
>>> On 2020/07/30 20:25, Johannes Thumshirn wrote:
>>>> When we loose a device for whatever reason while (re)scanning zones, we
>>>> trip over a NULL pointer in blk_revalidate_zone_cb, like in the following
>>>> log:
>>>>
>>>> sd 0:0:0:0: [sda] 3418095616 4096-byte logical blocks: (14.0 TB/12.7 TiB)
>>>> sd 0:0:0:0: [sda] 52156 zones of 65536 logical blocks
>>>> sd 0:0:0:0: [sda] Write Protect is off
>>>> sd 0:0:0:0: [sda] Mode Sense: 37 00 00 08
>>>> sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
>>>> sd 0:0:0:0: [sda] REPORT ZONES start lba 1065287680 failed
>>>> sd 0:0:0:0: [sda] REPORT ZONES: Result: hostbyte=0x00 driverbyte=0x08
>>>> sd 0:0:0:0: [sda] Sense Key : 0xb [current]
>>>> sd 0:0:0:0: [sda] ASC=0x0 ASCQ=0x6
>>>> sda: failed to revalidate zones
>>>> sd 0:0:0:0: [sda] 0 4096-byte logical blocks: (0 B/0 B)
>>>> sda: detected capacity change from 14000519643136 to 0
>>>> ==================================================================
>>>> BUG: KASAN: null-ptr-deref in blk_revalidate_zone_cb+0x1b7/0x550
>>>> Write of size 8 at addr 0000000000000010 by task kworker/u4:1/58
>>>>
>>>> CPU: 1 PID: 58 Comm: kworker/u4:1 Not tainted 5.8.0-rc1 #692
>>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
>>>> Workqueue: events_unbound async_run_entry_fn
>>>> Call Trace:
>>>>  dump_stack+0x7d/0xb0
>>>>  ? blk_revalidate_zone_cb+0x1b7/0x550
>>>>  kasan_report.cold+0x5/0x37
>>>>  ? blk_revalidate_zone_cb+0x1b7/0x550
>>>>  check_memory_region+0x145/0x1a0
>>>>  blk_revalidate_zone_cb+0x1b7/0x550
>>>>  sd_zbc_parse_report+0x1f1/0x370
>>>>  ? blk_req_zone_write_trylock+0x200/0x200
>>>>  ? sectors_to_logical+0x60/0x60
>>>>  ? blk_req_zone_write_trylock+0x200/0x200
>>>>  ? blk_req_zone_write_trylock+0x200/0x200
>>>>  sd_zbc_report_zones+0x3c4/0x5e0
>>>>  ? sd_dif_config_host+0x500/0x500
>>>>  blk_revalidate_disk_zones+0x231/0x44d
>>>>  ? _raw_write_lock_irqsave+0xb0/0xb0
>>>>  ? blk_queue_free_zone_bitmaps+0xd0/0xd0
>>>>  sd_zbc_read_zones+0x8cf/0x11a0
>>>>  sd_revalidate_disk+0x305c/0x64e0
>>>>  ? __device_add_disk+0x776/0xf20
>>>>  ? read_capacity_16.part.0+0x1080/0x1080
>>>>  ? blk_alloc_devt+0x250/0x250
>>>>  ? create_object.isra.0+0x595/0xa20
>>>>  ? kasan_unpoison_shadow+0x33/0x40
>>>>  sd_probe+0x8dc/0xcd2
>>>>  really_probe+0x20e/0xaf0
>>>>  __driver_attach_async_helper+0x249/0x2d0
>>>>  async_run_entry_fn+0xbe/0x560
>>>>  process_one_work+0x764/0x1290
>>>>  ? _raw_read_unlock_irqrestore+0x30/0x30
>>>>  worker_thread+0x598/0x12f0
>>>>  ? __kthread_parkme+0xc6/0x1b0
>>>>  ? schedule+0xed/0x2c0
>>>>  ? process_one_work+0x1290/0x1290
>>>>  kthread+0x36b/0x440
>>>>  ? kthread_create_worker_on_cpu+0xa0/0xa0
>>>>  ret_from_fork+0x22/0x30
>>>> ==================================================================
>>>>
>>>> When the device is already gone we end up with the following scenario:
>>>> The device's capacity is 0 and thus the number of zones will be 0 as well. When
>>>> allocating the bitmap for the conventional zones, we then trip over a NULL
>>>> pointer.
>>>>
>>>> So if we encounter a zoned block device with a 0 capacity, don't dare to
>>>> revalidate the zones sizes.
>>>>
>>>> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
>>>> ---
>>>>
>>>> Note: This is a hot-fix for 5.8, we're working on something to make a
>>>> recoverable error recoverable.
>>>>
>>>>
>>>>  block/blk-zoned.c | 3 +++
>>>>  1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
>>>> index 23831fa8701d..480dfff69a00 100644
>>>> --- a/block/blk-zoned.c
>>>> +++ b/block/blk-zoned.c
>>>> @@ -497,6 +497,9 @@ int blk_revalidate_disk_zones(struct gendisk *disk,
>>>>  	if (WARN_ON_ONCE(!queue_is_mq(q)))
>>>>  		return -EIO;
>>>>  
>>>> +	if (!get_capacity(disk))
>>>> +		return -EIO;
>>>> +
>>>>  	/*
>>>>  	 * Ensure that all memory allocations in this context are done as if
>>>>  	 * GFP_NOIO was specified.
>>>>
>>>
>>> I reworked sd_zbc_read_zones() and sd_zbc_revalidate_zones() to allow recovering
>>> from simple temporary errors and avoid this problem. Will send the patch
>>> tomorrow or so after some more testing.
>>>
>>> But even with that patch applied, I think this patch makes the generic block
>>> code more solid. So:
>>>
>>> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
>>>
>>>
>>
>> Jens any chance we can still get this into 5.8?
> 
> I'm not going to push this out now, if 5.8 is being cut on Sunday. If we
> happen to get an -rc8, then it's not impossible.
> 
> But this isn't a regression in this merge window as far as I can tell,
> so really shouldn't be critical to get in. Marking it for stable etc and
> queueing for 5.9 may be the saner approach, imho.
> 

You're right. When I wrote this I was still under the impression it's a 
regression I did introduce with the zone append series.

Anyway, thanks for pulling in.