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AJvYcCVCa0n27xw6xZzRTd9EoOLHuQQ8K//01ErKeF1CQwyr0o+NAlqb+LzIp1pt79IxsSAkBAFZ/l7cfwcv2PU2aY4=@vger.kernel.org X-Gm-Message-State: AOJu0YxW4zgnCTf0N+UvL4L6kZB/dL20GrsIpv1UOXdBn8ZQO+RogsnT LhRm1jpM6man1nhLsOy4FF6KY93ZW+Zf7sFApEMHeD652YJ26hnR32RNXHilceCvNqhuL6/dr7Z 1XuM/tQ== X-Google-Smtp-Source: AGHT+IGoGwd/Y8vsxaXkZq3lcq5gV0uAcPoWJqxGcCejiu9rQZwPdtbf9qfiVIzoSAsbfmD8Xw6SbN6aqVM= X-Received: from plnz4.prod.google.com ([2002:a17:902:8344:b0:231:e2fb:ebf]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ccd0:b0:234:e655:a62e with SMTP id d9443c01a7336-235e101356bmr63542455ad.9.1749078748733; Wed, 04 Jun 2025 16:12:28 -0700 (PDT) Date: Wed, 4 Jun 2025 16:11:51 -0700 In-Reply-To: <20250604231151.799834-1-surenb@google.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250604231151.799834-1-surenb@google.com> X-Mailer: git-send-email 2.49.0.1266.g31b7d2e469-goog Message-ID: <20250604231151.799834-8-surenb@google.com> Subject: [PATCH v4 7/7] mm/maps: execute PROCMAP_QUERY ioctl under per-vma locks From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, vbabka@suse.cz, peterx@redhat.com, jannh@google.com, hannes@cmpxchg.org, mhocko@kernel.org, paulmck@kernel.org, shuah@kernel.org, adobriyan@gmail.com, brauner@kernel.org, josef@toxicpanda.com, yebin10@huawei.com, linux@weissschuh.net, willy@infradead.org, osalvador@suse.de, andrii@kernel.org, ryan.roberts@arm.com, christophe.leroy@csgroup.eu, tjmercier@google.com, kaleshsingh@google.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, surenb@google.com Utilize per-vma locks to stabilize vma after lookup without taking mmap_lock during PROCMAP_QUERY ioctl execution. While we might take mmap_lock for reading during contention, we do that momentarily only to lock the vma. This change is designed to reduce mmap_lock contention and prevent PROCMAP_QUERY ioctl calls from blocking address space updates. Signed-off-by: Suren Baghdasaryan --- fs/proc/task_mmu.c | 56 ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 44 insertions(+), 12 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 36d883c4f394..93ba35a84975 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -550,28 +550,60 @@ static int pid_maps_open(struct inode *inode, struct file *file) PROCMAP_QUERY_VMA_FLAGS \ ) -static int query_vma_setup(struct mm_struct *mm) +#ifdef CONFIG_PER_VMA_LOCK + +static int query_vma_setup(struct proc_maps_private *priv) { - return mmap_read_lock_killable(mm); + rcu_read_lock(); + priv->locked_vma = NULL; + priv->mmap_locked = false; + + return 0; } -static void query_vma_teardown(struct mm_struct *mm, struct vm_area_struct *vma) +static void query_vma_teardown(struct proc_maps_private *priv) { - mmap_read_unlock(mm); + unlock_vma(priv); + rcu_read_unlock(); +} + +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_private *priv, + unsigned long addr) +{ + vma_iter_init(&priv->iter, priv->mm, addr); + return get_next_vma(priv, addr); +} + +#else /* CONFIG_PER_VMA_LOCK */ + +static int query_vma_setup(struct proc_maps_private *priv) +{ + return mmap_read_lock_killable(priv->mm); +} + +static void query_vma_teardown(struct proc_maps_private *priv) +{ + mmap_read_unlock(priv->mm); } -static struct vm_area_struct *query_vma_find_by_addr(struct mm_struct *mm, unsigned long addr) +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_private *priv, + unsigned long addr) { - return find_vma(mm, addr); + return find_vma(priv->mm, addr); } -static struct vm_area_struct *query_matching_vma(struct mm_struct *mm, +#endif /* CONFIG_PER_VMA_LOCK */ + +static struct vm_area_struct *query_matching_vma(struct proc_maps_private *priv, unsigned long addr, u32 flags) { struct vm_area_struct *vma; next_vma: - vma = query_vma_find_by_addr(mm, addr); + vma = query_vma_find_by_addr(priv, addr); + if (IS_ERR(vma)) + return vma; + if (!vma) goto no_vma; @@ -647,13 +679,13 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) if (!mm || !mmget_not_zero(mm)) return -ESRCH; - err = query_vma_setup(mm); + err = query_vma_setup(priv); if (err) { mmput(mm); return err; } - vma = query_matching_vma(mm, karg.query_addr, karg.query_flags); + vma = query_matching_vma(priv, karg.query_addr, karg.query_flags); if (IS_ERR(vma)) { err = PTR_ERR(vma); vma = NULL; @@ -738,7 +770,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) } /* unlock vma or mmap_lock, and put mm_struct before copying data to user */ - query_vma_teardown(mm, vma); + query_vma_teardown(priv); mmput(mm); if (karg.vma_name_size && copy_to_user(u64_to_user_ptr(karg.vma_name_addr), @@ -758,7 +790,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) return 0; out: - query_vma_teardown(mm, vma); + query_vma_teardown(priv); mmput(mm); kfree(name_buf); return err;