[PATCH for-next v10 5/7] block: factor out bio_map_get helper

[Jens Axboe]

On 9/28/22 11:49 AM, Jens Axboe wrote:
>> Not really new in this code but a question to Jens:  The existing
>> bio_map_user_iov has no real upper bounds on the number of bios
>> allocated, how does that fit with the very limited pool size of
>> fs_bio_set?
> 
> Good question - I think we'd need to ensure that once we get
> past the initial alloc that we clear any gfp flags that'd make
> the mempool_alloc() wait for completions.

Either that, or just have the passthrough code use non-waiting flags to
begin with. Not guaranteeing forward progress is a bit iffy though...
But in practice it'd be no different than getting a failure due to OOM
because the application submitted a big request and we needed to alloc
and map multiple bios.

-- 
Jens Axboe