[PATCH 5/8] FOLD: don't use in_task() to decide for offloading

[Christoph Hellwig <hch@lst.de>]

As described in commit c99fab6e80b76, some block drivers might call
into ->bi_end_io from non-preemptible context.  Copy and past the
logic from that commit, although having a core helper for it would
be nicer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/bio.h | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 45c311e5ff71..72664807c757 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -375,6 +375,16 @@ static inline struct bio *bio_alloc(struct block_device *bdev,
 
 void submit_bio(struct bio *bio);
 
+/* Offload from atomic contexts to minimize scheduling overhead */
+static inline bool bio_in_atomic(void)
+{
+	if (IS_ENABLED(CONFIG_PREEMPTION) && rcu_preempt_depth())
+		return true;
+	if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
+		return true;
+	return !preemptible();
+}
+
 void __bio_complete_in_task(struct bio *bio);
 
 /**
@@ -386,10 +396,11 @@ void __bio_complete_in_task(struct bio *bio);
  */
 static inline bool bio_complete_in_task(struct bio *bio)
 {
-	if (in_task())
-		return false;
-	__bio_complete_in_task(bio);
-	return true;
+	if (bio_in_atomic()) {
+		__bio_complete_in_task(bio);
+		return true;
+	}
+	return false;
 }
 
 extern void bio_endio(struct bio *);
-- 
2.47.3