Re: [RFC PATCH] locking/percpu-rwsem: use this_cpu_{inc|dec}() for read_count

[Boaz Harrosh]

On 17/09/2020 15:48, Matthew Wilcox wrote:
> On Thu, Sep 17, 2020 at 02:01:33PM +0200, Oleg Nesterov wrote:
<>
> If we change bio_endio to invoke the ->bi_end_io callbacks in softirq
> context instead of hardirq context, we can change the pagecache to take
> BH-safe locks instead of IRQ-safe locks.  I believe the only reason the
> lock needs to be IRQ-safe is for the benefit of paths like:

From my totally subjective experience on the filesystem side (user of 
bio_endio) all HW block drivers I used including Nvme isci, sata... etc. 
end up calling bio_endio in softirq. The big exception to that is the 
vdX drivers under KVM. Which is very Ironic to me.
I wish we could make all drivers be uniform in this regard.

But maybe I'm just speaking crap. Its only from my limited debuging 
expirience.

Thanks
Boaz