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[134.134.136.126]) by mx.google.com with ESMTPS id w12si3046417pgr.55.2019.06.07.15.37.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 07 Jun 2019 15:37:03 -0700 (PDT) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 134.134.136.126 as permitted sender) client-ip=134.134.136.126; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 134.134.136.126 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Jun 2019 15:37:02 -0700 X-ExtLoop1: 1 Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by orsmga004.jf.intel.com with ESMTP; 07 Jun 2019 15:37:01 -0700 Date: Fri, 7 Jun 2019 15:38:16 -0700 From: Ira Weiny To: Jason Gunthorpe Cc: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com, linux-rdma@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, Jason Gunthorpe Subject: Re: [PATCH v2 hmm 03/11] mm/hmm: Hold a mmgrab from hmm to mm Message-ID: <20190607223815.GE14559@iweiny-DESK2.sc.intel.com> References: <20190606184438.31646-1-jgg@ziepe.ca> <20190606184438.31646-4-jgg@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190606184438.31646-4-jgg@ziepe.ca> User-Agent: Mutt/1.11.1 (2018-12-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 06, 2019 at 03:44:30PM -0300, Jason Gunthorpe wrote: > From: Jason Gunthorpe > > So long a a struct hmm pointer exists, so should the struct mm it is > linked too. Hold the mmgrab() as soon as a hmm is created, and mmdrop() it > once the hmm refcount goes to zero. > > Since mmdrop() (ie a 0 kref on struct mm) is now impossible with a !NULL > mm->hmm delete the hmm_hmm_destroy(). > > Signed-off-by: Jason Gunthorpe > Reviewed-by: Jérôme Glisse Reviewed-by: Ira Weiny > --- > v2: > - Fix error unwind paths in hmm_get_or_create (Jerome/Jason) > --- > include/linux/hmm.h | 3 --- > kernel/fork.c | 1 - > mm/hmm.c | 22 ++++------------------ > 3 files changed, 4 insertions(+), 22 deletions(-) > > diff --git a/include/linux/hmm.h b/include/linux/hmm.h > index 2d519797cb134a..4ee3acabe5ed22 100644 > --- a/include/linux/hmm.h > +++ b/include/linux/hmm.h > @@ -586,14 +586,11 @@ static inline int hmm_vma_fault(struct hmm_mirror *mirror, > } > > /* Below are for HMM internal use only! Not to be used by device driver! */ > -void hmm_mm_destroy(struct mm_struct *mm); > - > static inline void hmm_mm_init(struct mm_struct *mm) > { > mm->hmm = NULL; > } > #else /* IS_ENABLED(CONFIG_HMM_MIRROR) */ > -static inline void hmm_mm_destroy(struct mm_struct *mm) {} > static inline void hmm_mm_init(struct mm_struct *mm) {} > #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */ > > diff --git a/kernel/fork.c b/kernel/fork.c > index b2b87d450b80b5..588c768ae72451 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -673,7 +673,6 @@ void __mmdrop(struct mm_struct *mm) > WARN_ON_ONCE(mm == current->active_mm); > mm_free_pgd(mm); > destroy_context(mm); > - hmm_mm_destroy(mm); > mmu_notifier_mm_destroy(mm); > check_mm(mm); > put_user_ns(mm->user_ns); > diff --git a/mm/hmm.c b/mm/hmm.c > index 8796447299023c..cc7c26fda3300e 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -29,6 +29,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -82,6 +83,7 @@ static struct hmm *hmm_get_or_create(struct mm_struct *mm) > hmm->notifiers = 0; > hmm->dead = false; > hmm->mm = mm; > + mmgrab(hmm->mm); > > spin_lock(&mm->page_table_lock); > if (!mm->hmm) > @@ -109,6 +111,7 @@ static struct hmm *hmm_get_or_create(struct mm_struct *mm) > mm->hmm = NULL; > spin_unlock(&mm->page_table_lock); > error: > + mmdrop(hmm->mm); > kfree(hmm); > return NULL; > } > @@ -130,6 +133,7 @@ static void hmm_free(struct kref *kref) > mm->hmm = NULL; > spin_unlock(&mm->page_table_lock); > > + mmdrop(hmm->mm); > mmu_notifier_call_srcu(&hmm->rcu, hmm_free_rcu); > } > > @@ -138,24 +142,6 @@ static inline void hmm_put(struct hmm *hmm) > kref_put(&hmm->kref, hmm_free); > } > > -void hmm_mm_destroy(struct mm_struct *mm) > -{ > - struct hmm *hmm; > - > - spin_lock(&mm->page_table_lock); > - hmm = mm_get_hmm(mm); > - mm->hmm = NULL; > - if (hmm) { > - hmm->mm = NULL; > - hmm->dead = true; > - spin_unlock(&mm->page_table_lock); > - hmm_put(hmm); > - return; > - } > - > - spin_unlock(&mm->page_table_lock); > -} > - > static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm) > { > struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier); > -- > 2.21.0 >