From: John Hubbard <jhubbard@nvidia.com>
To: Jan Kara <jack@suse.cz>
Cc: "Michal Hocko" <mhocko@suse.com>,
kvm@vger.kernel.org, linux-doc@vger.kernel.org,
"David Airlie" <airlied@linux.ie>,
"Dave Chinner" <david@fromorbit.com>,
dri-devel@lists.freedesktop.org,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, "Paul Mackerras" <paulus@samba.org>,
linux-kselftest@vger.kernel.org,
"Ira Weiny" <ira.weiny@intel.com>,
"Jonathan Corbet" <corbet@lwn.net>,
linux-rdma@vger.kernel.org,
"Christoph Hellwig" <hch@infradead.org>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Björn Töpel" <bjorn.topel@intel.com>,
linux-media@vger.kernel.org, "Shuah Khan" <shuah@kernel.org>,
linux-block@vger.kernel.org, "Jérôme Glisse" <jglisse@redhat.com>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Dan Williams" <dan.j.williams@intel.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
bpf@vger.kernel.org,
"Magnus Karlsson" <magnus.karlsson@intel.com>,
"Jens Axboe" <axboe@kernel.dk>,
netdev@vger.kernel.org,
"Alex Williamson" <alex.williamson@redhat.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
linux-fsdevel@vger.kernel.org,
"Andrew Morton" <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org,
"David S . Miller" <davem@davemloft.net>,
"Mike Kravetz" <mike.kravetz@oracle.com>
Subject: Re: [PATCH v6 17/24] mm/gup: track FOLL_PIN pages
Date: Tue, 19 Nov 2019 23:17:16 -0800 [thread overview]
Message-ID: <92d0385a-90be-e900-e5ec-1eeafd24ff81@nvidia.com> (raw)
In-Reply-To: <20191119113746.GD25605@quack2.suse.cz>
On 11/19/19 3:37 AM, Jan Kara wrote:
> On Tue 19-11-19 00:16:36, John Hubbard wrote:
>> @@ -2025,6 +2149,20 @@ static int __record_subpages(struct page *page, unsigned long addr,
>> return nr;
>> }
>>
>> +static bool __pin_compound_head(struct page *head, int refs, unsigned int flags)
>> +{
>
> I don't quite like the proliferation of names starting with __. I don't
> think there's a good reason for that, particularly in this case. Also 'pin'
> here is somewhat misleading as we already use term "pin" for the particular
> way of pinning the page. We could have grab_compound_head() or maybe
> nail_compound_head() :), but you're native speaker so you may come up with
> better word.
Yes, it is ugly naming, I'll change these as follows:
__pin_compound_head() --> grab_compound_head()
__record_subpages() --> record_subpages()
I loved the "nail_compound_head()" suggestion, it just seems very vivid, but
in the end, I figured I'd better keep it relatively drab and colorless. :)
>
>> + if (flags & FOLL_PIN) {
>> + if (unlikely(!try_pin_compound_head(head, refs)))
>> + return false;
>> + } else {
>> + head = try_get_compound_head(head, refs);
>> + if (!head)
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> static void put_compound_head(struct page *page, int refs)
>> {
>> /* Do a get_page() first, in case refs == page->_refcount */
>
> put_compound_head() needs similar treatment as undo_dev_pagemap(), doesn't
> it?
>
Yes, will fix that up.
>> @@ -968,7 +973,18 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
>> if (!*pgmap)
>> return ERR_PTR(-EFAULT);
>> page = pfn_to_page(pfn);
>> - get_page(page);
>> +
>> + if (flags & FOLL_GET)
>> + get_page(page);
>> + else if (flags & FOLL_PIN) {
>> + /*
>> + * try_pin_page() is not actually expected to fail here because
>> + * we hold the pmd lock so no one can unmap the pmd and free the
>> + * page that it points to.
>> + */
>> + if (unlikely(!try_pin_page(page)))
>> + page = ERR_PTR(-EFAULT);
>> + }
>
> This pattern is rather common. So maybe I'd add a helper grab_page(page,
> flags) doing
>
> if (flags & FOLL_GET)
> get_page(page);
> else if (flags & FOLL_PIN)
> return try_pin_page(page);
> return true;
>
OK.
> Otherwise the patch looks good to me now.
>
> Honza
Great! I thought I'd have a v7 out today, but fate decided to have me repair
my test machine instead. So, soon. ha. :)
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2019-11-20 7:19 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-19 8:16 [PATCH v6 00/24] mm/gup: track dma-pinned pages: FOLL_PIN John Hubbard
2019-11-19 8:16 ` [PATCH v6 01/24] mm/gup: pass flags arg to __gup_device_* functions John Hubbard
2019-11-19 8:16 ` [PATCH v6 02/24] mm/gup: factor out duplicate code from four routines John Hubbard
2019-11-19 10:19 ` Jan Kara
2019-11-19 8:16 ` [PATCH v6 03/24] mm/gup: move try_get_compound_head() to top, fix minor issues John Hubbard
2019-11-19 8:16 ` [PATCH v6 04/24] mm: Cleanup __put_devmap_managed_page() vs ->page_free() John Hubbard
2019-11-19 8:16 ` [PATCH v6 05/24] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages John Hubbard
2019-11-19 8:16 ` [PATCH v6 06/24] goldish_pipe: rename local pin_user_pages() routine John Hubbard
2019-11-19 8:16 ` [PATCH v6 07/24] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-11-19 8:16 ` [PATCH v6 08/24] media/v4l2-core: set pages dirty upon releasing DMA buffers John Hubbard
2019-11-19 8:16 ` [PATCH v6 09/24] vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM John Hubbard
2019-11-19 8:16 ` [PATCH v6 10/24] mm/gup: introduce pin_user_pages*() and FOLL_PIN John Hubbard
2019-11-19 8:16 ` [PATCH v6 11/24] goldish_pipe: convert to pin_user_pages() and put_user_page() John Hubbard
2019-11-19 8:16 ` [PATCH v6 12/24] IB/{core, hw, umem}: set FOLL_PIN via pin_user_pages*(), fix up ODP John Hubbard
2019-11-19 8:16 ` [PATCH v6 13/24] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() John Hubbard
2019-11-19 8:16 ` [PATCH v6 14/24] drm/via: set FOLL_PIN via pin_user_pages_fast() John Hubbard
2019-11-19 8:16 ` [PATCH v6 15/24] fs/io_uring: set FOLL_PIN via pin_user_pages() John Hubbard
2019-11-19 16:10 ` Jens Axboe
2019-11-20 7:03 ` John Hubbard
2019-11-19 8:16 ` [PATCH v6 16/24] net/xdp: " John Hubbard
2019-11-19 8:16 ` [PATCH v6 17/24] mm/gup: track FOLL_PIN pages John Hubbard
2019-11-19 11:37 ` Jan Kara
2019-11-20 7:17 ` John Hubbard [this message]
2019-11-19 8:16 ` [PATCH v6 18/24] media/v4l2-core: pin_user_pages (FOLL_PIN) and put_user_page() conversion John Hubbard
2019-11-19 8:16 ` [PATCH v6 19/24] vfio, mm: " John Hubbard
2019-11-19 8:16 ` [PATCH v6 20/24] powerpc: book3s64: convert to pin_user_pages() and put_user_page() John Hubbard
2019-11-19 8:16 ` [PATCH v6 21/24] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" John Hubbard
2019-11-19 8:16 ` [PATCH v6 22/24] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2019-11-19 8:16 ` [PATCH v6 23/24] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
2019-11-19 8:16 ` [PATCH v6 24/24] mm, tree-wide: rename put_user_page*() to unpin_user_page*() John Hubbard
2019-11-19 11:39 ` Jan Kara
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=92d0385a-90be-e900-e5ec-1eeafd24ff81@nvidia.com \
--to=jhubbard@nvidia.com \
--cc=airlied@linux.ie \
--cc=akpm@linux-foundation.org \
--cc=alex.williamson@redhat.com \
--cc=axboe@kernel.dk \
--cc=bjorn.topel@intel.com \
--cc=bpf@vger.kernel.org \
--cc=corbet@lwn.net \
--cc=dan.j.williams@intel.com \
--cc=daniel@ffwll.ch \
--cc=davem@davemloft.net \
--cc=david@fromorbit.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=hch@infradead.org \
--cc=ira.weiny@intel.com \
--cc=jack@suse.cz \
--cc=jgg@ziepe.ca \
--cc=jglisse@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-rdma@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=magnus.karlsson@intel.com \
--cc=mchehab@kernel.org \
--cc=mhocko@suse.com \
--cc=mike.kravetz@oracle.com \
--cc=netdev@vger.kernel.org \
--cc=paulus@samba.org \
--cc=shuah@kernel.org \
--cc=vbabka@suse.cz \
--cc=viro@zeniv.linux.org.uk \
/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).