On 2020-05-11 16:18, Bart Van Assche wrote:
> Anyway, can you give the patch below a try?
The patch in my previous email handles MQ mode but not bio mode. The
attached patch should handle both.
Thanks,
Bart.
>From f3fcdf9000226dc1354557eae53d4541d4059d03 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche@xxxxxxx>
Date: Mon, 11 May 2020 15:21:02 -0700
Subject: [PATCH] null_blk: Zero-initialize read buffers
---
drivers/block/null_blk_main.c | 45 +++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 06f5761fccb6..39dd82683e10 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -1250,8 +1250,53 @@ static inline blk_status_t null_handle_memory_backed(struct nullb_cmd *cmd,
return errno_to_blk_status(err);
}
+static void nullb_zero_bvec(const struct bio_vec *bvec)
+{
+ struct page *page = bvec->bv_page;
+ u32 offset = bvec->bv_offset;
+ u32 left = bvec->bv_len;
+
+ while (left) {
+ u32 len = min_t(u32, left, PAGE_SIZE - offset);
+ void *kaddr;
+
+ kaddr = kmap_atomic(page);
+ memset(kaddr + offset, 0, len);
+ kunmap_atomic(kaddr);
+ page++;
+ left -= len;
+ offset = 0;
+ }
+}
+
+static void nullb_zero_bio_data_buffer(struct bio *bio)
+{
+ struct bvec_iter iter;
+ struct bio_vec bvec;
+
+ bio_for_each_bvec(bvec, bio, iter)
+ nullb_zero_bvec(&bvec);
+}
+
+static void nullb_zero_rq_data_buffer(const struct request *rq)
+{
+ struct req_iterator iter;
+ struct bio_vec bvec;
+
+ rq_for_each_bvec(bvec, rq, iter)
+ nullb_zero_bvec(&bvec);
+}
+
+/* Complete a request. Only called if dev->memory_backed == 0. */
static inline void nullb_complete_cmd(struct nullb_cmd *cmd)
{
+ struct nullb_device *dev = cmd->nq->dev;
+
+ if (dev->queue_mode == NULL_Q_BIO && bio_op(cmd->bio) == REQ_OP_READ)
+ nullb_zero_bio_data_buffer(cmd->bio);
+ else if (req_op(cmd->rq) == REQ_OP_READ)
+ nullb_zero_rq_data_buffer(cmd->rq);
+
/* Complete IO by inline, softirq or timer */
switch (cmd->nq->dev->irqmode) {
case NULL_IRQ_SOFTIRQ:
