[PATCH] fix

[Minchan Kim]

Not-yet-Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
 drivers/block/zram/zram_drv.c | 40 ++++++++++++++--------------------------
 1 file changed, 14 insertions(+), 26 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index bcb03bacdded..516c3bd97a28 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -147,8 +147,7 @@ static inline bool valid_io_request(struct zram *zram,
 
 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 {
-	if (*offset + bvec->bv_len >= PAGE_SIZE)
-		(*index)++;
+	*index  += (*offset + bvec->bv_len) / PAGE_SIZE;
 	*offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 }
 
@@ -886,7 +885,7 @@ static void __zram_make_request(struct zram *zram, struct bio *bio)
 {
 	int offset;
 	u32 index;
-	struct bio_vec bvec;
+	struct bio_vec bvec, bv;
 	struct bvec_iter iter;
 
 	index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT;
@@ -900,34 +899,23 @@ static void __zram_make_request(struct zram *zram, struct bio *bio)
 	}
 
 	bio_for_each_segment(bvec, bio, iter) {
-		int max_transfer_size = PAGE_SIZE - offset;
+		int remained_size = bvec.bv_len;
+		int transfer_size;
 
-		if (bvec.bv_len > max_transfer_size) {
-			/*
-			 * zram_bvec_rw() can only make operation on a single
-			 * zram page. Split the bio vector.
-			 */
-			struct bio_vec bv;
-
-			bv.bv_page = bvec.bv_page;
-			bv.bv_len = max_transfer_size;
-			bv.bv_offset = bvec.bv_offset;
+		bv.bv_page = bvec.bv_page;
+		bv.bv_offset = bvec.bv_offset;
+		do {
+			transfer_size = min_t(int, PAGE_SIZE, remained_size);
+			bv.bv_len = transfer_size;
 
 			if (zram_bvec_rw(zram, &bv, index, offset,
-					 op_is_write(bio_op(bio))) < 0)
-				goto out;
-
-			bv.bv_len = bvec.bv_len - max_transfer_size;
-			bv.bv_offset += max_transfer_size;
-			if (zram_bvec_rw(zram, &bv, index + 1, 0,
-					 op_is_write(bio_op(bio))) < 0)
-				goto out;
-		} else
-			if (zram_bvec_rw(zram, &bvec, index, offset,
-					 op_is_write(bio_op(bio))) < 0)
+					op_is_write(bio_op(bio))) < 0)
 				goto out;
 
-		update_position(&index, &offset, &bvec);
+			bv.bv_offset += transfer_size;
+			update_position(&index, &offset, &bv);
+			remained_size -= transfer_size;
+		} while (remained_size);
 	}
 
 	bio_endio(bio);
-- 
2.7.4


> 
> > 
> > Anyway, to me, it's really subtle at this moment so I doubt it should
> > be stable material. :(
> 
> I'm not quite sure, it's at least 4.11 material. See above.

Absolutely agree that it should be 4.11 material but I don't want to
backport it to the stable because it would make regression due to
split bio works.

Anyway, if my patch I attached works for you, I will resend this
with modified descriptions includes more detail.

Thanks for the help!!