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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 16 Apr 2019 14:46:26 +0100 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3GDkPQA33620156 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 16 Apr 2019 13:46:25 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 19B424C040; Tue, 16 Apr 2019 13:46:25 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A7D134C046; Tue, 16 Apr 2019 13:46:23 +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 13:46:23 +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 Subject: [PATCH v12 21/31] mm: Introduce find_vma_rcu() Date: Tue, 16 Apr 2019 15:45:12 +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: 19041613-4275-0000-0000-000003287656 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19041613-4276-0000-0000-00003837A75D Message-Id: <20190416134522.17540-22-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=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=966 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904160093 X-Mailman-Approved-At: Wed, 17 Apr 2019 06:55:22 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, npiggin@gmail.com, linux-mm@kvack.org, paulmck@linux.vnet.ibm.com, Tim Chen , haren@linux.vnet.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" This allows to search for a VMA structure without holding the mmap_sem. The search is repeated while the mm seqlock is changing and until we found a valid VMA. While under the RCU protection, a reference is taken on the VMA, so the caller must call put_vma() once it not more need the VMA structure. At the time a VMA is inserted in the MM RB tree, in vma_rb_insert(), a reference is taken to the VMA by calling get_vma(). When removing a VMA from the MM RB tree, the VMA is not release immediately but at the end of the RCU grace period through vm_rcu_put(). This ensures that the VMA remains allocated until the end the RCU grace period. Since the vm_file pointer, if valid, is released in put_vma(), there is no guarantee that the file pointer will be valid on the returned VMA. Signed-off-by: Laurent Dufour --- include/linux/mm_types.h | 1 + mm/internal.h | 5 ++- mm/mmap.c | 76 ++++++++++++++++++++++++++++++++++++++-- 3 files changed, 78 insertions(+), 4 deletions(-) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 6a6159e11a3f..9af6694cb95d 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -287,6 +287,7 @@ struct vm_area_struct { #ifdef CONFIG_SPECULATIVE_PAGE_FAULT atomic_t vm_ref_count; + struct rcu_head vm_rcu; #endif struct rb_node vm_rb; diff --git a/mm/internal.h b/mm/internal.h index 302382bed406..1e368e4afe3c 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -55,7 +55,10 @@ static inline void put_vma(struct vm_area_struct *vma) __free_vma(vma); } -#else +extern struct vm_area_struct *find_vma_rcu(struct mm_struct *mm, + unsigned long addr); + +#else /* CONFIG_SPECULATIVE_PAGE_FAULT */ static inline void get_vma(struct vm_area_struct *vma) { diff --git a/mm/mmap.c b/mm/mmap.c index c106440dcae7..34bf261dc2c8 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -179,6 +179,18 @@ static inline void mm_write_sequnlock(struct mm_struct *mm) { write_sequnlock(&mm->mm_seq); } + +static void __vm_rcu_put(struct rcu_head *head) +{ + struct vm_area_struct *vma = container_of(head, struct vm_area_struct, + vm_rcu); + put_vma(vma); +} +static void vm_rcu_put(struct vm_area_struct *vma) +{ + VM_BUG_ON_VMA(!RB_EMPTY_NODE(&vma->vm_rb), vma); + call_rcu(&vma->vm_rcu, __vm_rcu_put); +} #else static inline void mm_write_seqlock(struct mm_struct *mm) { @@ -190,6 +202,8 @@ static inline void mm_write_sequnlock(struct mm_struct *mm) void __free_vma(struct vm_area_struct *vma) { + if (IS_ENABLED(CONFIG_SPECULATIVE_PAGE_FAULT)) + VM_BUG_ON_VMA(!RB_EMPTY_NODE(&vma->vm_rb), vma); mpol_put(vma_policy(vma)); vm_area_free(vma); } @@ -197,11 +211,24 @@ void __free_vma(struct vm_area_struct *vma) /* * Close a vm structure and free it, returning the next. */ -static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) +static struct vm_area_struct *__remove_vma(struct vm_area_struct *vma) { struct vm_area_struct *next = vma->vm_next; might_sleep(); + if (IS_ENABLED(CONFIG_SPECULATIVE_PAGE_FAULT) && + !RB_EMPTY_NODE(&vma->vm_rb)) { + /* + * If the VMA is still linked in the RB tree, we must release + * that reference by calling put_vma(). + * This should only happen when called from exit_mmap(). + * We forcely clear the node to satisfy the chec in + * __free_vma(). This is safe since the RB tree is not walked + * anymore. + */ + RB_CLEAR_NODE(&vma->vm_rb); + put_vma(vma); + } if (vma->vm_ops && vma->vm_ops->close) vma->vm_ops->close(vma); if (vma->vm_file) @@ -211,6 +238,13 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) return next; } +static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) +{ + if (IS_ENABLED(CONFIG_SPECULATIVE_PAGE_FAULT)) + VM_BUG_ON_VMA(!RB_EMPTY_NODE(&vma->vm_rb), vma); + return __remove_vma(vma); +} + static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags, struct list_head *uf); SYSCALL_DEFINE1(brk, unsigned long, brk) @@ -475,7 +509,7 @@ static inline void vma_rb_insert(struct vm_area_struct *vma, /* All rb_subtree_gap values must be consistent prior to insertion */ validate_mm_rb(root, NULL); - + get_vma(vma); rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks); } @@ -491,6 +525,14 @@ static void __vma_rb_erase(struct vm_area_struct *vma, struct mm_struct *mm) mm_write_seqlock(mm); rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks); mm_write_sequnlock(mm); /* wmb */ +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + /* + * Ensure the removal is complete before clearing the node. + * Matched by vma_has_changed()/handle_speculative_fault(). + */ + RB_CLEAR_NODE(&vma->vm_rb); + vm_rcu_put(vma); +#endif } static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma, @@ -2331,6 +2373,34 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) EXPORT_SYMBOL(find_vma); +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT +/* + * Like find_vma() but under the protection of RCU and the mm sequence counter. + * The vma returned has to be relaesed by the caller through the call to + * put_vma() + */ +struct vm_area_struct *find_vma_rcu(struct mm_struct *mm, unsigned long addr) +{ + struct vm_area_struct *vma = NULL; + unsigned int seq; + + do { + if (vma) + put_vma(vma); + + seq = read_seqbegin(&mm->mm_seq); + + rcu_read_lock(); + vma = find_vma(mm, addr); + if (vma) + get_vma(vma); + rcu_read_unlock(); + } while (read_seqretry(&mm->mm_seq, seq)); + + return vma; +} +#endif + /* * Same as find_vma, but also return a pointer to the previous VMA in *pprev. */ @@ -3231,7 +3301,7 @@ void exit_mmap(struct mm_struct *mm) while (vma) { if (vma->vm_flags & VM_ACCOUNT) nr_accounted += vma_pages(vma); - vma = remove_vma(vma); + vma = __remove_vma(vma); } vm_unacct_memory(nr_accounted); } -- 2.21.0