[RESEND PATCH] Don't reinvent the wheel but use existing llilst API

[Byungchul Park]

Hello Linus,

Even though llist APIs exist, serveral code in kernel reinvent the
implementation again and again. Since I think it's *worth* making it use
existing APIs, I submit patches doing it.

Actually I've submitted them to maintainers and commiters about 10 times
for 4 months, but they seem to be too busy to review or take them. Of
course you might be even busier, but it would be appriciated if you do
that instead. It might not take your time much since they are simple.

Patches worked on scheduler, irq_work, vhost/scsi and raid are already
taken by proper maintainers. For now, only ones for bcache, mm, fput and
namespace remain.

Thank you,
Byungchul