From: Matthew Wilcox <willy@infradead.org>
To: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Michel Lespinasse <walken@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>,
Liam Howlett <Liam.Howlett@oracle.com>,
Jerome Glisse <jglisse@redhat.com>,
Davidlohr Bueso <dave@stgolabs.net>,
David Rientjes <rientjes@google.com>,
Hugh Dickins <hughd@google.com>, Ying Han <yinghan@google.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap_lock
Date: Tue, 19 May 2020 08:32:51 -0700 [thread overview]
Message-ID: <20200519153251.GY16070@bombadil.infradead.org> (raw)
In-Reply-To: <7c540ac9-ba44-7187-5dc2-60b4c761e91c@linux.ibm.com>
On Tue, May 19, 2020 at 03:20:40PM +0200, Laurent Dufour wrote:
> Le 19/05/2020 à 15:10, Michel Lespinasse a écrit :
> > On Mon, May 18, 2020 at 03:45:22PM +0200, Laurent Dufour wrote:
> > > Le 24/04/2020 à 03:39, Michel Lespinasse a écrit :
> > > > Rename the mmap_sem field to mmap_lock. Any new uses of this lock
> > > > should now go through the new mmap locking api. The mmap_lock is
> > > > still implemented as a rwsem, though this could change in the future.
> > > >
> > > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > > > index dc9ef302f517..701f3995f621 100644
> > > > --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > > > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > > > @@ -661,7 +661,7 @@ static int etnaviv_gem_userptr_get_pages(struct etnaviv_gem_object *etnaviv_obj)
> > > > struct etnaviv_gem_userptr *userptr = &etnaviv_obj->userptr;
> > > > int ret, pinned = 0, npages = etnaviv_obj->base.size >> PAGE_SHIFT;
> > > > - might_lock_read(¤t->mm->mmap_sem);
> > > > + might_lock_read(¤t->mm->mmap_lock);
> > >
> > > Why not a mm_might_lock_read() new API to hide the mmap_lock, and add it to
> > > the previous patch?
> >
> > I'm not sure why this is needed - we may rework the lock to be
> > something else than rwsem, but might_lock_read should still apply to
> > it and make sense ? I'm not sure what the extra API would bring...
>
> I guess at one time the API would become might_lock_read_a_range(), isn't it?
> Furthermore this would hiding the lock's name which the goal of this series.
I think this assertion should be deleted from this driver. It's there
in case get_user_pages_fast() takes the mmap sem. It would make sense to
have this assertion in get_user_pages_fast() in case we take the fast path
which doesn't acquire the mmap_sem. Something like this:
+++ b/mm/gup.c
@@ -2754,6 +2754,7 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
FOLL_FORCE | FOLL_PIN | FOLL_GET)))
return -EINVAL;
+ might_lock_read(¤t->mm->mmap_lock);
start = untagged_addr(start) & PAGE_MASK;
addr = start;
len = (unsigned long) nr_pages << PAGE_SHIFT;
next prev parent reply other threads:[~2020-05-19 15:32 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-22 0:14 [PATCH v5 00/10] Add a new mmap locking API wrapping mmap_sem calls Michel Lespinasse
2020-04-22 0:14 ` [PATCH v5 01/10] mmap locking API: initial implementation as rwsem wrappers Michel Lespinasse
2020-05-18 9:28 ` Vlastimil Babka
2020-05-18 13:18 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 02/10] MMU notifier: use the new mmap locking API Michel Lespinasse
2020-05-18 9:28 ` Vlastimil Babka
2020-05-18 13:19 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 03/10] DMA reservations: " Michel Lespinasse
2020-05-18 9:30 ` Vlastimil Babka
2020-05-18 13:20 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 04/10] mmap locking API: use coccinelle to convert mmap_sem rwsem call sites Michel Lespinasse
2020-05-18 9:36 ` Vlastimil Babka
2020-05-18 13:21 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 05/10] mmap locking API: convert mmap_sem call sites missed by coccinelle Michel Lespinasse
2020-05-18 9:44 ` Vlastimil Babka
2020-05-18 13:23 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 06/10] mmap locking API: convert nested write lock sites Michel Lespinasse
2020-05-18 10:32 ` Vlastimil Babka
2020-05-19 12:54 ` Michel Lespinasse
2020-05-18 13:24 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 07/10] mmap locking API: add mmap_read_trylock_non_owner() Michel Lespinasse
2020-05-18 10:42 ` Vlastimil Babka
2020-04-22 0:14 ` [PATCH v5 08/10] mmap locking API: add MMAP_LOCK_INITIALIZER Michel Lespinasse
2020-05-18 10:45 ` Vlastimil Babka
2020-05-19 12:56 ` Michel Lespinasse
2020-05-18 13:33 ` Laurent Dufour
2020-04-22 0:14 ` [PATCH v5 09/10] mmap locking API: add mmap_assert_locked Michel Lespinasse
2020-04-22 2:10 ` Michel Lespinasse
2020-04-22 2:18 ` Matthew Wilcox
2020-04-24 1:44 ` Michel Lespinasse
2020-04-22 0:14 ` [PATCH v5 10/10] mmap locking API: rename mmap_sem to mmap_lock Michel Lespinasse
2020-04-22 1:58 ` Matthew Wilcox
2020-04-22 22:54 ` Michel Lespinasse
2020-04-23 1:59 ` Matthew Wilcox
2020-04-24 1:26 ` Michel Lespinasse
2020-04-24 1:38 ` [PATCH v5.5 09/10] mmap locking API: add mmap_assert_locked() and mmap_assert_write_locked() Michel Lespinasse
2020-05-18 11:01 ` Vlastimil Babka
2020-05-19 13:06 ` Michel Lespinasse
2020-04-24 1:39 ` [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap_lock Michel Lespinasse
2020-05-18 11:07 ` Vlastimil Babka
2020-05-19 13:12 ` Michel Lespinasse
2020-05-18 13:45 ` Laurent Dufour
2020-05-19 13:10 ` Michel Lespinasse
2020-05-19 13:20 ` Laurent Dufour
2020-05-19 15:32 ` Matthew Wilcox [this message]
2020-05-19 18:14 ` John Hubbard
2020-05-20 2:39 ` Michel Lespinasse
2020-05-20 7:32 ` John Hubbard
2020-05-20 8:02 ` Michel Lespinasse
2020-05-20 12:48 ` Jason Gunthorpe
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