Re: [PATCH 8/8] scsi: ufs: Check for completion from the timeout handler

["Peter Wang (王信友)" <peter.wang@mediatek.com>]

On Mon, 2024-06-17 at 14:07 -0700, Bart Van Assche wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  If ufshcd_abort() returns SUCCESS for an already completed command
> then
> that command is completed twice. This results in a crash. Prevent
> this by
> checking whether a command has completed without completion interrupt
> from
> the timeout handler. This CL fixes the following kernel crash:
> 
> Unable to handle kernel NULL pointer dereference at virtual address
> 0000000000000000
> Call trace:
>  dma_direct_map_sg+0x70/0x274
>  scsi_dma_map+0x84/0x124
>  ufshcd_queuecommand+0x3fc/0x880
>  scsi_queue_rq+0x7d0/0x111c
>  blk_mq_dispatch_rq_list+0x440/0xebc
>  blk_mq_do_dispatch_sched+0x5a4/0x6b8
>  __blk_mq_sched_dispatch_requests+0x150/0x220
>  __blk_mq_run_hw_queue+0xf0/0x218
>  __blk_mq_delay_run_hw_queue+0x8c/0x18c
>  blk_mq_run_hw_queue+0x1a4/0x360
>  blk_mq_sched_insert_requests+0x130/0x334
>  blk_mq_flush_plug_list+0x138/0x234
>  blk_flush_plug_list+0x118/0x164
>  blk_finish_plug()
>  read_pages+0x38c/0x408
>  page_cache_ra_unbounded+0x230/0x2f8
>  do_sync_mmap_readahead+0x1a4/0x208
>  filemap_fault+0x27c/0x8f4
>  f2fs_filemap_fault+0x28/0xfc
>  __do_fault+0xc4/0x208
>  handle_pte_fault+0x290/0xe04
>  do_handle_mm_fault+0x52c/0x858
>  do_page_fault+0x5dc/0x798
>  do_translation_fault+0x40/0x54
>  do_mem_abort+0x60/0x134
>  el0_da+0x40/0xb8
>  el0t_64_sync_handler+0xc4/0xe4
>  el0t_64_sync+0x1b4/0x1b8
> 

Hi Bart,

This backtrace is ufshcd_queuecommand KE.
If ufshcd_abort() complete an already completed command, 
it should be KE with ufshcd_abort backtrace?

More, if a command is completed by irq.
The rq may be release and ufshcd_mcq_req_to_hwq(hba, rq) will get KE
Here is our backtrace of this case.

platform +platform:112b0000.ufshci ufshcd-mtk 112b0000.ufshci:
ufshcd_try_to_abort_task: cmd at tag 41 not pending in the device.
platform +platform:112b0000.ufshci ufshcd-mtk 112b0000.ufshci:
ufshcd_try_to_abort_task: cmd at tag=41 is cleared.
platform +platform:112b0000.ufshci ufshcd-mtk 112b0000.ufshci: Aborting
tag 41 / CDB 0x28 succeeded
  Unable to handle kernel NULL pointer dereference at virtual address
0000000000000194
  pc : [0xffffffddd7a79bf8] blk_mq_unique_tag+0x8/0x14
  lr : [0xffffffddd6155b84] ufshcd_mcq_req_to_hwq+0x1c/0x40
[ufs_mediatek_mod_ise]
   do_mem_abort+0x58/0x118
   el1_abort+0x3c/0x5c
   el1h_64_sync_handler+0x54/0x90
   el1h_64_sync+0x68/0x6c
   blk_mq_unique_tag+0x8/0x14
   ufshcd_err_handler+0xae4/0xfa8 [ufs_mediatek_mod_ise]
   process_one_work+0x208/0x4fc
   worker_thread+0x228/0x438
   kthread+0x104/0x1d4
   ret_from_fork+0x10/0x20

Thanks.
Peter



> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>  drivers/ufs/core/ufshcd.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index e3835e61e4b1..47cc0802c4f4 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -8922,7 +8922,28 @@ static void ufshcd_async_scan(void *data,
> async_cookie_t cookie)
>  
>  static enum scsi_timeout_action ufshcd_eh_timed_out(struct scsi_cmnd
> *scmd)
>  {
> -struct ufs_hba *hba = shost_priv(scmd->device->host);
> +struct scsi_device *sdev = scmd->device;
> +struct ufs_hba *hba = shost_priv(sdev->host);
> +struct scsi_cmnd *cmd2 = scmd;
> +const u32 unique_tag = blk_mq_unique_tag(scsi_cmd_to_rq(scmd));
> +
> +WARN_ON_ONCE(!scmd);
> +
> +if (is_mcq_enabled(hba)) {
> +struct request *rq = scsi_cmd_to_rq(scmd);
> +struct ufs_hw_queue *hwq = ufshcd_mcq_req_to_hwq(hba, rq);
> +
> +ufshcd_mcq_poll_cqe_lock(hba, hwq, &cmd2);
> +} else {
> +__ufshcd_poll(hba->host, UFSHCD_POLL_FROM_INTERRUPT_CONTEXT,
> +      &cmd2);
> +}
> +if (cmd2 == NULL) {
> +sdev_printk(KERN_INFO, sdev,
> +    "%s: cmd with tag %#x has already been completed\n",
> +    __func__, unique_tag);
> +return SCSI_EH_DONE;
> +}
>  
>  if (!hba->system_suspending) {
>  /* Activate the error handler in the SCSI core. */