From: Gal Pressman <galpress@amazon.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Michal Kalderon <michal.kalderon@marvell.com>,
<mkalderon@marvell.com>, <aelior@marvell.com>,
<dledford@redhat.com>, <bmt@zurich.ibm.com>, <sleybo@amazon.com>,
<leon@kernel.org>, <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH v11 rdma-next 6/7] RDMA/qedr: Add doorbell overflow recovery support
Date: Fri, 20 Sep 2019 17:00:25 +0300 [thread overview]
Message-ID: <82541758-3e72-d485-6923-cf3336a4297a@amazon.com> (raw)
In-Reply-To: <20190920133817.GB7095@ziepe.ca>
On 20/09/2019 16:38, Jason Gunthorpe wrote:
> On Fri, Sep 20, 2019 at 04:30:52PM +0300, Gal Pressman wrote:
>> On 19/09/2019 21:02, Jason Gunthorpe wrote:
>>> On Thu, Sep 05, 2019 at 01:01:16PM +0300, Michal Kalderon wrote:
>>>
>>>> @@ -347,6 +360,9 @@ void qedr_mmap_free(struct rdma_user_mmap_entry *rdma_entry)
>>>> {
>>>> struct qedr_user_mmap_entry *entry = get_qedr_mmap_entry(rdma_entry);
>>>>
>>>> + if (entry->mmap_flag == QEDR_USER_MMAP_PHYS_PAGE)
>>>> + free_page((unsigned long)phys_to_virt(entry->address));
>>>> +
>>>
>>> While it isn't wrong it do it this way, we don't need this mmap_free()
>>> stuff for normal CPU pages. Those are refcounted and qedr can simply
>>> call free_page() during the teardown of the uobject that is using the
>>> this page. This is what other drivers already do.
>>
>> This is pretty much what EFA does as well. When we allocate pages
>> for the user (CQ for example), we DMA map them and later on mmap
>> them to the user. We expect those pages to remain until the entry is
>> freed, how can we call free_page, who is holding a refcount on those
>> except for the driver?
>
> free_page is kind of a lie, it is more like put_page (see
> __free_pages). I think the difference is that it assumes the page came
> from alloc_page and skips some generic stuff when freeing it.
>
> When the driver does vm_insert_page the vma holds another refcount and
> the refcount does not go to zero until that page drops out of the
> vma (ie at the same time mmap_free above is called).
>
> Then __put_page will do the free_unref_page(), etc.
>
> So for CPU pages it is fine to not use mmap_free so long as
> vm_insert_page is used
Thanks, I did not know this, it simplifies things.
In that case, maybe the mmap_free callback is redundant.
next prev parent reply other threads:[~2019-09-20 14:01 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-05 10:01 [PATCH v11 rdma-next 0/7] RDMA/qedr: Use the doorbell overflow recovery mechanism for RDMA Michal Kalderon
2019-09-05 10:01 ` [PATCH v11 rdma-next 1/7] RDMA/core: Move core content from ib_uverbs to ib_core Michal Kalderon
2019-09-05 10:01 ` [PATCH v11 rdma-next 2/7] RDMA/core: Create mmap database and cookie helper functions Michal Kalderon
2019-09-19 17:14 ` Jason Gunthorpe
2019-09-19 17:48 ` Jason Gunthorpe
2019-09-19 18:07 ` Jason Gunthorpe
2019-09-23 9:36 ` [EXT] " Michal Kalderon
2019-09-23 13:30 ` Jason Gunthorpe
2019-09-24 8:31 ` Michal Kalderon
2019-09-24 12:37 ` Jason Gunthorpe
2019-09-05 10:01 ` [PATCH v11 rdma-next 3/7] RDMA/efa: Use the common mmap_xa helpers Michal Kalderon
2019-09-19 17:37 ` Jason Gunthorpe
2019-09-23 9:15 ` Michal Kalderon
2019-09-23 13:28 ` Jason Gunthorpe
2019-09-05 10:01 ` [PATCH v11 rdma-next 4/7] RDMA/siw: " Michal Kalderon
2019-09-05 10:01 ` [PATCH v11 rdma-next 5/7] RDMA/qedr: Use the common mmap API Michal Kalderon
2019-09-19 17:55 ` Jason Gunthorpe
2019-09-20 13:39 ` Gal Pressman
2019-09-23 9:21 ` Michal Kalderon
2019-09-23 13:29 ` Jason Gunthorpe
2019-09-24 8:25 ` [EXT] " Michal Kalderon
2019-09-24 8:49 ` Pressman, Gal
2019-09-24 9:31 ` Michal Kalderon
2019-10-20 7:19 ` Gal Pressman
2019-10-21 17:33 ` Jason Gunthorpe
2019-10-23 6:40 ` Gal Pressman
2019-10-23 14:41 ` Jason Gunthorpe
2019-10-24 8:06 ` Gal Pressman
2019-09-05 10:01 ` [PATCH v11 rdma-next 6/7] RDMA/qedr: Add doorbell overflow recovery support Michal Kalderon
2019-09-19 18:02 ` Jason Gunthorpe
2019-09-20 13:30 ` Gal Pressman
2019-09-20 13:38 ` Jason Gunthorpe
2019-09-20 14:00 ` Gal Pressman [this message]
2019-09-23 9:37 ` Michal Kalderon
2019-09-25 19:16 ` [EXT] " Michal Kalderon
2019-09-25 19:21 ` Jason Gunthorpe
2019-09-25 19:37 ` Michal Kalderon
2019-09-26 19:10 ` Jason Gunthorpe
2019-09-23 9:30 ` Michal Kalderon
2019-09-23 13:26 ` Jason Gunthorpe
2019-09-05 10:01 ` [PATCH v11 rdma-next 7/7] RDMA/qedr: Add iWARP doorbell " Michal Kalderon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=82541758-3e72-d485-6923-cf3336a4297a@amazon.com \
--to=galpress@amazon.com \
--cc=aelior@marvell.com \
--cc=bmt@zurich.ibm.com \
--cc=dledford@redhat.com \
--cc=jgg@ziepe.ca \
--cc=leon@kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=michal.kalderon@marvell.com \
--cc=mkalderon@marvell.com \
--cc=sleybo@amazon.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).