block: don't use for-inside-for in bio_for_each_segment_all

Commit 6dc4f100c175 ("block: allow bio_for_each_segment_all() to
iterate over multi-page bvec") changes bio_for_each_segment_all()
to use for-inside-for.

This way breaks all bio_for_each_segment_all() call with error out
branch via 'break', since now 'break' can only break from the inner
loop.

Fixes this issue by implementing bio_for_each_segment_all() via
single 'for' loop, and now the logic is very similar with normal
bvec iterator.

Cc: Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc: linux-btrfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: Omar Sandoval <osandov@fb.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reported-and-Tested-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
Fixes: 6dc4f100c175 ("block: allow bio_for_each_segment_all() to iterate over multi-page bvec")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 22 insertions, 12 deletions

diff --git a/include/linux/bio.h b/include/linux/bio.h
index bb6090aa165d..e584673c1881 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -120,19 +120,23 @@ static inline bool bio_full(struct bio *bio)
         return bio->bi_vcnt >= bio->bi_max_vecs;
 }
 
-#define mp_bvec_for_each_segment(bv, bvl, i, iter_all)                  \
-        for (bv = bvec_init_iter_all(&iter_all);                        \
-                (iter_all.done < (bvl)->bv_len) &&                      \
-                (mp_bvec_next_segment((bvl), &iter_all), 1);            \
-                iter_all.done += bv->bv_len, i += 1)
+static inline bool bio_next_segment(const struct bio *bio,
+                                    struct bvec_iter_all *iter)
+{
+        if (iter->idx >= bio->bi_vcnt)
+                return false;
+
+        bvec_advance(&bio->bi_io_vec[iter->idx], iter);
+        return true;
+}
 
 /*
  * drivers should _never_ use the all version - the bio may have been split
  * before it got to the driver and the driver won't own all of it
  */
-#define bio_for_each_segment_all(bvl, bio, i, iter_all)         \
-        for (i = 0, iter_all.idx = 0; iter_all.idx < (bio)->bi_vcnt; iter_all.idx++)    \
-                mp_bvec_for_each_segment(bvl, &((bio)->bi_io_vec[iter_all.idx]), i, iter_all)
+#define bio_for_each_segment_all(bvl, bio, i, iter)                     \
+        for (i = 0, bvl = bvec_init_iter_all(&iter);                    \
+             bio_next_segment((bio), &iter); i++)
 
 static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
                                     unsigned bytes)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index f6275c4da13a..3bc91879e1e2 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -145,18 +145,18 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
 
 static inline struct bio_vec *bvec_init_iter_all(struct bvec_iter_all *iter_all)
 {
-        iter_all->bv.bv_page = NULL;
         iter_all->done = 0;
+        iter_all->idx = 0;
 
         return &iter_all->bv;
 }
 
-static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
-                                        struct bvec_iter_all *iter_all)
+static inline void bvec_advance(const struct bio_vec *bvec,
+                                struct bvec_iter_all *iter_all)
 {
         struct bio_vec *bv = &iter_all->bv;
 
-        if (bv->bv_page) {
+        if (iter_all->done) {
                 bv->bv_page = nth_page(bv->bv_page, 1);
                 bv->bv_offset = 0;
         } else {
@@ -165,6 +165,12 @@ static inline void mp_bvec_next_segment(const struct bio_vec *bvec,
         }
         bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
                            bvec->bv_len - iter_all->done);
+        iter_all->done += bv->bv_len;
+
+        if (iter_all->done == bvec->bv_len) {
+                iter_all->idx++;
+                iter_all->done = 0;
+        }
 }
 
 /*