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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 16 Apr 2019 14:46:24 +0100 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3GDkMSN40894698 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 16 Apr 2019 13:46:22 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 983514C040; Tue, 16 Apr 2019 13:46:22 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 326344C044; Tue, 16 Apr 2019 13:46:21 +0000 (GMT) Received: from nimbus.lab.toulouse-stg.fr.ibm.com (unknown [9.101.4.33]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 16 Apr 2019 13:46:21 +0000 (GMT) From: Laurent Dufour To: akpm@linux-foundation.org, mhocko@kernel.org, peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , aneesh.kumar@linux.ibm.com, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , sergey.senozhatsky.work@gmail.com, Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, Daniel Jordan , David Rientjes , Jerome Glisse , Ganesh Mahendran , Minchan Kim , Punit Agrawal , vinayak menon , Yang Shi , zhong jiang , Haiyan Song , Balbir Singh , sj38.park@gmail.com, Michel Lespinasse , Mike Rapoport Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, npiggin@gmail.com, paulmck@linux.vnet.ibm.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: [PATCH v12 20/31] mm: introduce vma reference counter Date: Tue, 16 Apr 2019 15:45:11 +0200 X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190416134522.17540-1-ldufour@linux.ibm.com> References: <20190416134522.17540-1-ldufour@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19041613-4275-0000-0000-000003287655 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19041613-4276-0000-0000-00003837A75C Message-Id: <20190416134522.17540-21-ldufour@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-16_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904160093 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: The final goal is to be able to use a VMA structure without holding the mmap_sem and to be sure that the structure will not be freed in our back. The lockless use of the VMA will be done through RCU protection and thus a dedicated freeing service is required to manage it asynchronously. As reported in a 2010's thread [1], this may impact file handling when a file is still referenced while the mapping is no more there. As the final goal is to handle anonymous VMA in a speculative way and not file backed mapping, we could close and free the file pointer in a synchronous way, as soon as we are guaranteed to not use it without holding the mmap_sem. For sanity reason, in a minimal effort, the vm_file file pointer is unset once the file pointer is put. [1] https://lore.kernel.org/linux-mm/20100104182429.833180340@chello.nl/ Signed-off-by: Laurent Dufour --- include/linux/mm.h | 4 ++++ include/linux/mm_types.h | 3 +++ mm/internal.h | 27 +++++++++++++++++++++++++++ mm/mmap.c | 13 +++++++++---- 4 files changed, 43 insertions(+), 4 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f14b2c9ddfd4..f761a9c65c74 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -529,6 +529,9 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm) vma->vm_mm = mm; vma->vm_ops = &dummy_vm_ops; INIT_LIST_HEAD(&vma->anon_vma_chain); +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + atomic_set(&vma->vm_ref_count, 1); +#endif } static inline void vma_set_anonymous(struct vm_area_struct *vma) @@ -1418,6 +1421,7 @@ static inline void INIT_VMA(struct vm_area_struct *vma) INIT_LIST_HEAD(&vma->anon_vma_chain); #ifdef CONFIG_SPECULATIVE_PAGE_FAULT seqcount_init(&vma->vm_sequence); + atomic_set(&vma->vm_ref_count, 1); #endif } diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 24b3f8ce9e42..6a6159e11a3f 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -285,6 +285,9 @@ struct vm_area_struct { /* linked list of VM areas per task, sorted by address */ struct vm_area_struct *vm_next, *vm_prev; +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + atomic_t vm_ref_count; +#endif struct rb_node vm_rb; /* diff --git a/mm/internal.h b/mm/internal.h index 9eeaf2b95166..302382bed406 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -40,6 +40,33 @@ void page_writeback_init(void); vm_fault_t do_swap_page(struct vm_fault *vmf); + +extern void __free_vma(struct vm_area_struct *vma); + +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT +static inline void get_vma(struct vm_area_struct *vma) +{ + atomic_inc(&vma->vm_ref_count); +} + +static inline void put_vma(struct vm_area_struct *vma) +{ + if (atomic_dec_and_test(&vma->vm_ref_count)) + __free_vma(vma); +} + +#else + +static inline void get_vma(struct vm_area_struct *vma) +{ +} + +static inline void put_vma(struct vm_area_struct *vma) +{ + __free_vma(vma); +} +#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */ + void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma, unsigned long floor, unsigned long ceiling); diff --git a/mm/mmap.c b/mm/mmap.c index f7f6027a7dff..c106440dcae7 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -188,6 +188,12 @@ static inline void mm_write_sequnlock(struct mm_struct *mm) } #endif /* CONFIG_SPECULATIVE_PAGE_FAULT */ +void __free_vma(struct vm_area_struct *vma) +{ + mpol_put(vma_policy(vma)); + vm_area_free(vma); +} + /* * Close a vm structure and free it, returning the next. */ @@ -200,8 +206,8 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) vma->vm_ops->close(vma); if (vma->vm_file) fput(vma->vm_file); - mpol_put(vma_policy(vma)); - vm_area_free(vma); + vma->vm_file = NULL; + put_vma(vma); return next; } @@ -990,8 +996,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, if (next->anon_vma) anon_vma_merge(vma, next); mm->map_count--; - mpol_put(vma_policy(next)); - vm_area_free(next); + put_vma(next); /* * In mprotect's case 6 (see comments on vma_merge), * we must remove another next too. It would clutter -- 2.21.0