linux-kernel - Re: [PATCH AUTOSEL 5.0 61/98] libceph: fix breakage caused by multipage bvecs

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Message-ID: <20190502125145.GC11584@sasha-vm>
Date:   Thu, 2 May 2019 08:51:45 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Ilya Dryomov <idryomov@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        Ceph Development <ceph-devel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH AUTOSEL 5.0 61/98] libceph: fix breakage caused by
 multipage bvecs

On Tue, Apr 23, 2019 at 10:28:56AM +0200, Ilya Dryomov wrote:
>On Mon, Apr 22, 2019 at 9:44 PM Sasha Levin <sashal@...nel.org> wrote:
>>
>> 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 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);
>
>Same here, shouldn't be needed.

Dropped, thanks!

--
Thanks,
Sasha