linux-kernel - [PATCH AUTOSEL 4.19 48/68] libceph: fix breakage caused by multipage bvecs

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Date:   Mon, 22 Apr 2019 15:44:56 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ilya Dryomov <idryomov@...il.com>, Sasha Levin <sashal@...nel.org>,
        ceph-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 48/68] libceph: fix breakage caused by multipage bvecs

From: Ilya Dryomov <idryomov@...il.com>

[ Upstream commit 187df76325af5d9e12ae9daec1510307797e54f0 ]

A bvec can now consist of multiple physically contiguous pages.
This means that bvec_iter_advance() can move to a different page while
staying in the same bvec (i.e. ->bi_bvec_done != 0).

The messenger works in terms of segments which can now be defined as
the smaller of a bvec and a page.  The "more bytes to process in this
segment" condition holds only if bvec_iter_advance() leaves us in the
same bvec _and_ in the same page.  On next bvec (possibly in the same
page) and on next page (possibly in the same bvec) we may need to set
->last_piece.

Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Sasha Levin (Microsoft) <sashal@...nel.org>
---
 net/ceph/messenger.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index f7d7f32ac673..ef5216206bdf 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -870,6 +870,7 @@ static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
 					size_t bytes)
 {
 	struct ceph_bio_iter *it = &cursor->bio_iter;
+	struct page *page = bio_iter_page(it->bio, it->iter);
 
 	BUG_ON(bytes > cursor->resid);
 	BUG_ON(bytes > bio_iter_len(it->bio, it->iter));
@@ -881,7 +882,8 @@ static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
 		return false;   /* no more data */
 	}
 
-	if (!bytes || (it->iter.bi_size && it->iter.bi_bvec_done))
+	if (!bytes || (it->iter.bi_size && it->iter.bi_bvec_done &&
+		       page == bio_iter_page(it->bio, it->iter)))
 		return false;	/* more bytes to process in this segment */
 
 	if (!it->iter.bi_size) {
@@ -929,6 +931,7 @@ static bool ceph_msg_data_bvecs_advance(struct ceph_msg_data_cursor *cursor,
 					size_t bytes)
 {
 	struct bio_vec *bvecs = cursor->data->bvec_pos.bvecs;
+	struct page *page = bvec_iter_page(bvecs, cursor->bvec_iter);
 
 	BUG_ON(bytes > cursor->resid);
 	BUG_ON(bytes > bvec_iter_len(bvecs, cursor->bvec_iter));
@@ -940,7 +943,8 @@ static bool ceph_msg_data_bvecs_advance(struct ceph_msg_data_cursor *cursor,
 		return false;   /* no more data */
 	}
 
-	if (!bytes || cursor->bvec_iter.bi_bvec_done)
+	if (!bytes || (cursor->bvec_iter.bi_bvec_done &&
+		       page == bvec_iter_page(bvecs, cursor->bvec_iter)))
 		return false;	/* more bytes to process in this segment */
 
 	BUG_ON(cursor->last_piece);
-- 
2.19.1