block: Kill bio_segments()/bi_vcnt usage

When we start sharing biovecs, keeping bi_vcnt accurate for splits is
going to be error prone - and unnecessary, if we refactor some code.

So bio_segments() has to go - but most of the existing users just needed
to know if the bio had multiple segments, which is easier - add a
bio_multiple_segments() for them.

(Two of the current uses of bio_segments() are going to go away in a
couple patches, but the current implementation of bio_segments() is
unsafe as soon as we start doing driver conversions for immutable
biovecs - so implement a dumb version for bisectability, it'll go away
in a couple patches)

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Neil Brown <neilb@suse.de>
Cc: Nagalakshmi Nandigama <Nagalakshmi.Nandigama@lsi.com>
Cc: Sreekanth Reddy <Sreekanth.Reddy@lsi.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>

1 files changed, 48 insertions, 33 deletions

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 930cb73c894b..aea9896a6289 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -97,13 +97,46 @@
 #define bio_offset(bio)         bio_iter_offset((bio), (bio)->bi_iter)
 #define bio_iovec(bio)          bio_iter_iovec((bio), (bio)->bi_iter)
 
-#define bio_segments(bio)       ((bio)->bi_vcnt - (bio)->bi_iter.bi_idx)
+#define bio_multiple_segments(bio)                              \
+        ((bio)->bi_iter.bi_size != bio_iovec(bio).bv_len)
 #define bio_sectors(bio)        ((bio)->bi_iter.bi_size >> 9)
 #define bio_end_sector(bio)     ((bio)->bi_iter.bi_sector + bio_sectors((bio)))
 
+/*
+ * Check whether this bio carries any data or not. A NULL bio is allowed.
+ */
+static inline bool bio_has_data(struct bio *bio)
+{
+        if (bio &&
+            bio->bi_iter.bi_size &&
+            !(bio->bi_rw & REQ_DISCARD))
+                return true;
+
+        return false;
+}
+
+static inline bool bio_is_rw(struct bio *bio)
+{
+        if (!bio_has_data(bio))
+                return false;
+
+        if (bio->bi_rw & BIO_NO_ADVANCE_ITER_MASK)
+                return false;
+
+        return true;
+}
+
+static inline bool bio_mergeable(struct bio *bio)
+{
+        if (bio->bi_rw & REQ_NOMERGE_FLAGS)
+                return false;
+
+        return true;
+}
+
 static inline unsigned int bio_cur_bytes(struct bio *bio)
 {
-        if (bio->bi_vcnt)
+        if (bio_has_data(bio))
                 return bio_iovec(bio).bv_len;
         else /* dataless requests such as discard */
                 return bio->bi_iter.bi_size;
@@ -111,7 +144,7 @@ static inline unsigned int bio_cur_bytes(struct bio *bio)
 
 static inline void *bio_data(struct bio *bio)
 {
-        if (bio->bi_vcnt)
+        if (bio_has_data(bio))
                 return page_address(bio_page(bio)) + bio_offset(bio);
 
         return NULL;
@@ -221,6 +254,18 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 
 #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)
 
+static inline unsigned bio_segments(struct bio *bio)
+{
+        unsigned segs = 0;
+        struct bio_vec bv;
+        struct bvec_iter iter;
+
+        bio_for_each_segment(bv, bio, iter)
+                segs++;
+
+        return segs;
+}
+
 /*
  * get a reference to a bio, so it won't disappear. the intended use is
  * something like:
@@ -435,36 +480,6 @@ static inline char *__bio_kmap_irq(struct bio *bio, unsigned short idx,
 #define bio_kunmap_irq(buf,flags)       __bio_kunmap_irq(buf, flags)
 
 /*
- * Check whether this bio carries any data or not. A NULL bio is allowed.
- */
-static inline bool bio_has_data(struct bio *bio)
-{
-        if (bio && bio->bi_vcnt)
-                return true;
-
-        return false;
-}
-
-static inline bool bio_is_rw(struct bio *bio)
-{
-        if (!bio_has_data(bio))
-                return false;
-
-        if (bio->bi_rw & REQ_WRITE_SAME)
-                return false;
-
-        return true;
-}
-
-static inline bool bio_mergeable(struct bio *bio)
-{
-        if (bio->bi_rw & REQ_NOMERGE_FLAGS)
-                return false;
-
-        return true;
-}
-
-/*
  * BIO list management for use by remapping drivers (e.g. DM or MD) and loop.
  *
  * A bio_list anchors a singly-linked list of bios chained through the bi_next