md/raid5: use bio_inc_remaining() instead of repurposing bi_phys_segments as a counter

md/raid5 needs to keep track of how many stripe_heads are processing a
bio so that it can delay calling bio_endio() until all stripe_heads
have completed.  It currently uses 16 bits of ->bi_phys_segments for
this purpose.

16 bits is only enough for 256M requests, and it is possible for a
single bio to be larger than this, which causes problems.  Also, the
bio struct contains a larger counter, __bi_remaining, which has a
purpose very similar to the purpose of our counter.  So stop using
->bi_phys_segments, and instead use __bi_remaining.

This means we don't need to initialize the counter, as our caller
initializes it to '1'.  It also means we can call bio_endio() directly
as it tests this counter internally.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 1 insertions, 16 deletions

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index fd5c21cde77f..7d74fb3f2ec6 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -488,8 +488,7 @@ static inline struct bio *r5_next_bio(struct bio *bio, sector_t sector)
 }
 
 /*
- * We maintain a biased count of active stripes in the bottom 16 bits of
- * bi_phys_segments, and a count of processed stripes in the upper 16 bits
+ * We maintain a count of processed stripes in the upper 16 bits
  */
 static inline int raid5_bi_processed_stripes(struct bio *bio)
 {
@@ -498,20 +497,6 @@ static inline int raid5_bi_processed_stripes(struct bio *bio)
 	return (atomic_read(segments) >> 16) & 0xffff;
 }
 
-static inline int raid5_dec_bi_active_stripes(struct bio *bio)
-{
-	atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
-
-	return atomic_sub_return(1, segments) & 0xffff;
-}
-
-static inline void raid5_inc_bi_active_stripes(struct bio *bio)
-{
-	atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
-
-	atomic_inc(segments);
-}
-
 static inline void raid5_set_bi_processed_stripes(struct bio *bio,
 	unsigned int cnt)
 {