Re: [PATCH] scsi: ufs: Fix proper API to send HPB pre-request

On 10/28/21 7:28 AM, James Bottomley wrote:

If the block people are happy with this, then I'm OK with it, but it
doesn't look like you've solved the fanout deadlock problem because
this new mechanism is still going to allocate a new tag.

(+Jens, Christoph and linux-block)

Hi James,

My understanding is that the UFS HPB code makes ufshcd_queuecommand()
return SCSI_MLQUEUE_HOST_BUSY if the pool with pre-allocated requests is
exhausted. This will make the SCSI core reissue a SCSI command until
completion of another command has freed up one of the pre-allocated
requests. This is not the most efficient approach but should not trigger
a deadlock.

Thanks,

Bart.