block: extend bio caching to task context

bio_put_percpu_cache() puts all non-iopoll bios into the irq-safe list,
which entails disabling irqs. The overhead of that is not that bad when
interrupts are already off but getting worse otherwise. We can optimise
it when we're in the task context by using ->free_list directly just as
the IOPOLL path does.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/4774e1a0f905f96c63174b0f3e4f79f0d9b63246.1707314970.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/bio.c

@@ -770,8 +770,9 @@ static inline void bio_put_percpu_cache(struct bio *bio)
 
 	bio_uninit(bio);
 
-	if ((bio->bi_opf & REQ_POLLED) && !WARN_ON_ONCE(in_interrupt())) {
+	if (in_task()) {
 		bio->bi_next = cache->free_list;
+		/* Not necessary but helps not to iopoll already freed bios */
 		bio->bi_bdev = NULL;
 		cache->free_list = bio;
 		cache->nr++;