[PATCH 3/3] block: Fix blk_end_request_all() for WRITE SAME requests

Bart Van Assche
2018-06-26T00:10:09Z

Most REQ_OP_WRITE_SAME requests have a data buffer size that differs
from the number of bytes affected on the storage medium. Since
blk_update_request() expects that its third argument is the number of
bytes that have been completed from the data out buffer, pass that
number fo blk_update_request(). This patch avoids that removing a
path controlled by the dm-mpath driver while mkfs is running triggers
the following kernel bug:

-----------[ cut here ]------------
kernel BUG at block/blk-core.c:3347!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 20 PID: 24369 Comm: mkfs.ext4 Not tainted 4.18.0-rc1-dbg+ #2
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.0.0-prebuilt.qemu-pro
ject.org 04/01/2014
RIP: 0010:blk_end_request_all+0x68/0x70
Call Trace:
<IRQ>
dm_softirq_done+0x326/0x3d0 [dm_mod]
blk_done_softirq+0x19b/0x1e0
__do_softirq+0x128/0x60d
irq_exit+0x100/0x110
smp_call_function_single_interrupt+0x90/0x330
call_function_single_interrupt+0xf/0x20
</IRQ>

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
---
block/blk-core.c | 31 ++++++++++++++++++++++++-------
block/blk-mq.c | 2 +-
block/blk.h | 2 ++
3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 81936b9d6d26..6f9483d4b988 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2686,6 +2686,21 @@ blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *
}
EXPORT_SYMBOL_GPL(blk_insert_cloned_request);

+/**
+ * blk_rq_bio_bytes - sum of all bytes in all bios associated with a request
+ * @rq: request pointer.
+ */
+unsigned int blk_rq_bio_bytes(const struct request *rq)
+{
+ unsigned int bytes = 0;
+ struct bio *bio;
+
+ for (bio = rq->bio; bio; bio = bio->bi_next)
+ bytes += bio->bi_iter.bi_size;
+
+ return bytes;
+}
+
/**
* blk_rq_err_bytes - determine number of bytes till the next failure boundary
* @rq: request to examine
@@ -3080,8 +3095,8 @@ EXPORT_SYMBOL_GPL(blk_steal_bios);
* (e.g. request-based dm) so that they can handle partial completion.
* Actual device drivers should use blk_end_request instead.
*
- * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
- * %false return from this function.
+ * Passing the result of blk_rq_bio_bytes() as @nr_bytes guarantees that
+ * this function will return %false.
*
* Return:
* %false - this request doesn't have any more data
@@ -3152,7 +3167,7 @@ bool blk_update_request(struct request *req, blk_status_t error,
* If total number of sectors is less than the first segment
* size, something has gone terribly wrong.
*/
- if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
+ if (blk_rq_bio_bytes(req) < blk_rq_cur_bytes(req)) {
blk_dump_rq_flags(req, "request botched");
req->__data_len = blk_rq_cur_bytes(req);
}
@@ -3341,9 +3356,10 @@ void blk_end_request_all(struct request *rq, blk_status_t error)
unsigned int bidi_bytes = 0;

if (unlikely(blk_bidi_rq(rq)))
- bidi_bytes = blk_rq_bytes(rq->next_rq);
+ bidi_bytes = blk_rq_bio_bytes(rq->next_rq);

- pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
+ pending = blk_end_bidi_request(rq, error, blk_rq_bio_bytes(rq),
+ bidi_bytes);
BUG_ON(pending);
}
EXPORT_SYMBOL(blk_end_request_all);
@@ -3388,9 +3404,10 @@ void __blk_end_request_all(struct request *rq, blk_status_t error)
WARN_ON_ONCE(rq->q->mq_ops);

if (unlikely(blk_bidi_rq(rq)))
- bidi_bytes = blk_rq_bytes(rq->next_rq);
+ bidi_bytes = blk_rq_bio_bytes(rq->next_rq);

- pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
+ pending = __blk_end_bidi_request(rq, error, blk_rq_bio_bytes(rq),
+ bidi_bytes);
BUG_ON(pending);
}
EXPORT_SYMBOL(__blk_end_request_all);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8c00fcd300b9..852a87895b90 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -543,7 +543,7 @@ EXPORT_SYMBOL(__blk_mq_end_request);

void blk_mq_end_request(struct request *rq, blk_status_t error)
{
- if (blk_update_request(rq, error, blk_rq_bytes(rq)))
+ if (blk_update_request(rq, error, blk_rq_bio_bytes(rq)))
BUG();
__blk_mq_end_request(rq, error);
}
diff --git a/block/blk.h b/block/blk.h
index a8f0f7986cfd..37a31d992c83 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -149,6 +149,8 @@ static inline void blk_queue_enter_live(struct request_queue *q)
percpu_ref_get(&q->q_usage_counter);
}

+unsigned int blk_rq_bio_bytes(const struct request *rq);
+
#ifdef CONFIG_BLK_DEV_INTEGRITY
void blk_flush_integrity(void);
bool __bio_integrity_endio(struct bio *);
--
2.17.1