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Y . Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Alexander Shishkin , Maxime Coquelin , Alexandre Torgue , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Bodo Stroesser , "Martin K . Petersen" , David Howells , Marc Dionne , Alexander Viro , Christian Brauner , Jan Kara , David Hildenbrand , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-mtd@lists.infradead.org, linux-staging@lists.linux.dev, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-afs@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ryan Roberts Subject: Re: [PATCH v4 05/21] mm: switch the rmap lock held option off in compat layer Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Stat-Signature: zobi7f71in85zf9s9t9o37iskynskxy8 X-Rspamd-Queue-Id: 06CEBA0002 X-Rspam-User: X-HE-Tag: 1774370122-194137 X-HE-Meta: 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 FdQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 24, 2026 at 03:26:28PM +0100, Vlastimil Babka (SUSE) wrote: > On 3/20/26 23:39, Lorenzo Stoakes (Oracle) wrote: > > In the mmap_prepare compatibility layer, we don't need to hold the rmap > > lock, as we are being called from an .mmap handler. > > > > The .mmap_prepare hook, when invoked in the VMA logic, is called prior to > > the VMA being instantiated, but the completion hook is called after the VMA > > is linked into the maple tree, meaning rmap walkers can reach it. > > > > The mmap hook does not link the VMA into the tree, so this cannot happen. > > > > Therefore it's safe to simply disable this in the mmap_prepare > > compatibility layer. > > > > Also update VMA tests code to reflect current compatibility layer state. > > > > Signed-off-by: Lorenzo Stoakes (Oracle) > > Acked-by: Vlastimil Babka (SUSE) > > a typo fix below, Andrew can fix locally? > > > --- > > mm/util.c | 6 ++++- > > tools/testing/vma/include/dup.h | 42 +++++++++++++++++---------------- > > 2 files changed, 27 insertions(+), 21 deletions(-) > > > > diff --git a/mm/util.c b/mm/util.c > > index a2cfa0d77c35..182f0f5cc400 100644 > > --- a/mm/util.c > > +++ b/mm/util.c > > @@ -1204,6 +1204,7 @@ int compat_vma_mmap(struct file *file, struct vm_area_struct *vma) > > > > .action.type = MMAP_NOTHING, /* Default */ > > }; > > + struct mmap_action *action = &desc.action; > > int err; > > > > err = vfs_mmap_prepare(file, &desc); > > @@ -1214,8 +1215,11 @@ int compat_vma_mmap(struct file *file, struct vm_area_struct *vma) > > if (err) > > return err; > > > > + /* being invoked from .mmmap means we don't have to enforce this. */ > > .mmap mmmmm map! ;) Andrew - could you fixup in place? Thanks. > > > + action->hide_from_rmap_until_complete = false; > > + > > set_vma_from_desc(vma, &desc); > > - err = mmap_action_complete(vma, &desc.action); > > + err = mmap_action_complete(vma, action); > > if (err) { > > const size_t len = vma_pages(vma) << PAGE_SHIFT; > >