[PATCH 4.14 057/146] block: dont let passthrough IO go into .make_request_fn()

Greg Kroah-Hartman
2018-01-01T14:42:05Z

From: Ming Lei <ming.lei@redhat.com>

commit 14cb0dc6479dc5ebc63b3a459a5d89a2f1b39fed upstream.

Commit a8821f3f3("block: Improvements to bounce-buffer handling") tries
to make sure that the bio to .make_request_fn won't exceed BIO_MAX_PAGES,
but ignores that passthrough I/O can use blk_queue_bounce() too.
Especially, passthrough IO may not be sector-aligned, and the check
of 'sectors < bio_sectors(*bio_orig)' inside __blk_queue_bounce() may
become true even though the max bvec number doesn't exceed BIO_MAX_PAGES,
then cause the bio splitted, and the original passthrough bio is submited
to generic_make_request().

This patch fixes this issue by checking if the bio is passthrough IO,
and use bio_kmalloc() to allocate the cloned passthrough bio.

Cc: NeilBrown <neilb@suse.com>
Fixes: a8821f3f3("block: Improvements to bounce-buffer handling")
Tested-by: Michele Ballabio <barra_cuda@katamail.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
block/bounce.c | 6 ++++--
include/linux/blkdev.h | 21 +++++++++++++++++++--
2 files changed, 23 insertions(+), 4 deletions(-)

--- a/block/bounce.c
+++ b/block/bounce.c
@@ -200,6 +200,7 @@ static void __blk_queue_bounce(struct re
unsigned i = 0;
bool bounce = false;
int sectors = 0;
+ bool passthrough = bio_is_passthrough(*bio_orig);

bio_for_each_segment(from, *bio_orig, iter) {
if (i++ < BIO_MAX_PAGES)
@@ -210,13 +211,14 @@ static void __blk_queue_bounce(struct re
if (!bounce)
return;

- if (sectors < bio_sectors(*bio_orig)) {
+ if (!passthrough && sectors < bio_sectors(*bio_orig)) {
bio = bio_split(*bio_orig, sectors, GFP_NOIO, bounce_bio_split);
bio_chain(bio, *bio_orig);
generic_make_request(*bio_orig);
*bio_orig = bio;
}
- bio = bio_clone_bioset(*bio_orig, GFP_NOIO, bounce_bio_set);
+ bio = bio_clone_bioset(*bio_orig, GFP_NOIO, passthrough ? NULL :
+ bounce_bio_set);

bio_for_each_segment_all(to, bio, i) {
struct page *page = to->bv_page;
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -241,14 +241,24 @@ struct request {
struct request *next_rq;
};

+static inline bool blk_op_is_scsi(unsigned int op)
+{
+ return op == REQ_OP_SCSI_IN || op == REQ_OP_SCSI_OUT;
+}
+
+static inline bool blk_op_is_private(unsigned int op)
+{
+ return op == REQ_OP_DRV_IN || op == REQ_OP_DRV_OUT;
+}
+
static inline bool blk_rq_is_scsi(struct request *rq)
{
- return req_op(rq) == REQ_OP_SCSI_IN || req_op(rq) == REQ_OP_SCSI_OUT;
+ return blk_op_is_scsi(req_op(rq));
}

static inline bool blk_rq_is_private(struct request *rq)
{
- return req_op(rq) == REQ_OP_DRV_IN || req_op(rq) == REQ_OP_DRV_OUT;
+ return blk_op_is_private(req_op(rq));
}

static inline bool blk_rq_is_passthrough(struct request *rq)
@@ -256,6 +266,13 @@ static inline bool blk_rq_is_passthrough
return blk_rq_is_scsi(rq) || blk_rq_is_private(rq);
}

+static inline bool bio_is_passthrough(struct bio *bio)
+{
+ unsigned op = bio_op(bio);
+
+ return blk_op_is_scsi(op) || blk_op_is_private(op);
+}
+
static inline unsigned short req_get_ioprio(struct request *req)
{
return req->ioprio;