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Subject[PATCH AUTOSEL 5.0 61/98] libceph: fix breakage caused by multipage bvecs
Date
From: Ilya Dryomov <idryomov@gmail.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@gmail.com>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.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 7e71b0df1fbc..3083988ce729 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -840,6 +840,7 @@ 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));
@@ -851,7 +852,8 @@ 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) {
@@ -899,6 +901,7 @@ 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));
@@ -910,7 +913,8 @@ 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
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