md/raid5: remove over-loading of ->bi_phys_segments.
When a read request, which bypassed the cache, fails, we need to retry
it through the cache.
This involves attaching it to a sequence of stripe_heads, and it may not
be possible to get all the stripe_heads we need at once.
We do what we can, and record how far we got in ->bi_phys_segments so
we can pick up again later.
There is only ever one bio which may have a non-zero offset stored in
->bi_phys_segments, the one that is either active in the single thread
which calls retry_aligned_read(), or is in conf->retry_read_aligned
waiting for retry_aligned_read() to be called again.
So we only need to store one offset value. This can be in a local
variable passed between remove_bio_from_retry() and
retry_aligned_read(), or in the r5conf structure next to the
->retry_read_aligned pointer.
Storing it there allows the last usage of ->bi_phys_segments to be
removed from md/raid5.c.
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 7d74fb3..cdc7f92 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -487,35 +487,6 @@ static inline struct bio *r5_next_bio(struct bio *bio, sector_t sector)
return NULL;
}
-/*
- * We maintain a count of processed stripes in the upper 16 bits
- */
-static inline int raid5_bi_processed_stripes(struct bio *bio)
-{
- atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
-
- return (atomic_read(segments) >> 16) & 0xffff;
-}
-
-static inline void raid5_set_bi_processed_stripes(struct bio *bio,
- unsigned int cnt)
-{
- atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
- int old, new;
-
- do {
- old = atomic_read(segments);
- new = (old & 0xffff) | (cnt << 16);
- } while (atomic_cmpxchg(segments, old, new) != old);
-}
-
-static inline void raid5_set_bi_stripes(struct bio *bio, unsigned int cnt)
-{
- atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
-
- atomic_set(segments, cnt);
-}
-
/* NOTE NR_STRIPE_HASH_LOCKS must remain below 64.
* This is because we sometimes take all the spinlocks
* and creating that much locking depth can cause
@@ -613,6 +584,7 @@ struct r5conf {
struct list_head delayed_list; /* stripes that have plugged requests */
struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */
struct bio *retry_read_aligned; /* currently retrying aligned bios */
+ unsigned int retry_read_offset; /* sector offset into retry_read_aligned */
struct bio *retry_read_aligned_list; /* aligned bios retry list */
atomic_t preread_active_stripes; /* stripes with scheduled io */
atomic_t active_aligned_reads;