[PATCH 05/10] block: bounce: don't access bio->bi_io_vec in copy_to_high_bio_irq

Ming Lei
2017-12-08T13:15:23Z

Firstly this patch introduce BVEC_ITER_ALL_INIT for iterating one bio
from start to end.

As we need to support multipage bvecs, so don't access bio->bi_io_vec
in copy_to_high_bio_irq(), and just use the standard iterator to do that.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
block/bounce.c | 16 +++++++++++-----
include/linux/bvec.h | 9 +++++++++
2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/block/bounce.c b/block/bounce.c
index 0274c31d6c05..c35a3d7f0528 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -113,24 +113,30 @@ int init_emergency_isa_pool(void)
static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
{
unsigned char *vfrom;
- struct bio_vec tovec, *fromvec = from->bi_io_vec;
+ struct bio_vec tovec, fromvec;
struct bvec_iter iter;
+ /*
+ * The bio of @from is created by bounce, so we can iterate
+ * its bvec from start to end, but the @from->bi_iter can't be
+ * trusted because it might be changed by splitting.
+ */
+ struct bvec_iter from_iter = BVEC_ITER_ALL_INIT;

bio_for_each_segment(tovec, to, iter) {
- if (tovec.bv_page != fromvec->bv_page) {
+ fromvec = bio_iter_iovec(from, from_iter);
+ if (tovec.bv_page != fromvec.bv_page) {
/*
* fromvec->bv_offset and fromvec->bv_len might have
* been modified by the block layer, so use the original
* copy, bounce_copy_vec already uses tovec->bv_len
*/
- vfrom = page_address(fromvec->bv_page) +
+ vfrom = page_address(fromvec.bv_page) +
tovec.bv_offset;

bounce_copy_vec(&tovec, vfrom);
flush_dcache_page(tovec.bv_page);
}
-
- fromvec++;
+ bio_advance_iter(from, &from_iter, tovec.bv_len);
}
}

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index ec8a4d7af6bd..fe7a22dd133b 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -125,4 +125,13 @@ static inline bool bvec_iter_rewind(const struct bio_vec *bv,
((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))

+/* for iterating one bio from start to end */
+#define BVEC_ITER_ALL_INIT (struct bvec_iter) \
+{ \
+ .bi_sector = 0, \
+ .bi_size = UINT_MAX, \
+ .bi_idx = 0, \
+ .bi_bvec_done = 0, \
+}
+
#endif /* __LINUX_BVEC_ITER_H */
--
2.9.5