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[156.34.49.251]) by smtp.gmail.com with ESMTPSA id r47sm18148670qtc.14.2019.05.23.08.34.38 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 23 May 2019 08:34:39 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hTpjp-0004zN-WB; Thu, 23 May 2019 12:34:38 -0300 From: Jason Gunthorpe To: linux-rdma@vger.kernel.org, linux-mm@kvack.org, Jerome Glisse , Ralph Campbell , John Hubbard Cc: Jason Gunthorpe Subject: [RFC PATCH 03/11] mm/hmm: Hold a mmgrab from hmm to mm Date: Thu, 23 May 2019 12:34:28 -0300 Message-Id: <20190523153436.19102-4-jgg@ziepe.ca> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190523153436.19102-1-jgg@ziepe.ca> References: <20190523153436.19102-1-jgg@ziepe.ca> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: 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 --- include/linux/hmm.h | 3 --- kernel/fork.c | 1 - mm/hmm.c | 21 +++------------------ 3 files changed, 3 insertions(+), 22 deletions(-) diff --git a/include/linux/hmm.h b/include/linux/hmm.h index 87d29e085a69f7..2a7346384ead13 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -584,14 +584,11 @@ 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 b4cba953040a0f..51b114ec6c395c 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -672,7 +672,6 @@ 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 fa1b04fcfc2549..e27058e92508b9 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) @@ -130,6 +132,7 @@ 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_fee_rcu); } @@ -138,24 +141,6 @@ 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