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From:   Davidlohr Bueso <dave@stgolabs.net>
To:     akpm@linux-foundation.org
Cc:     dledford@redhat.com, jgg@mellanox.com, jack@suse.de,
        ira.weiny@intel.com, linux-rdma@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        dave@stgolabs.net, Davidlohr Bueso <dbueso@suse.de>
Subject: [PATCH 1/6] mm: make mm->pinned_vm an atomic64 counter
Date:   Mon, 21 Jan 2019 09:42:15 -0800
Message-Id: <20190121174220.10583-2-dave@stgolabs.net>
In-Reply-To: <20190121174220.10583-1-dave@stgolabs.net>
References: <20190121174220.10583-1-dave@stgolabs.net>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Taking a sleeping lock to _only_ increment a variable is quite the
overkill, and pretty much all users do this. Furthermore, some drivers
(ie: infiniband and scif) that need pinned semantics can go to quite
some trouble to actually delay via workqueue (un)accounting for pinned
pages when not possible to acquire it.

By making the counter atomic we no longer need to hold the mmap_sem
and can simply some code around it for pinned_vm users. The counter
is 64-bit such that we need not worry about overflows such as rdma
user input controlled from userspace.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 drivers/infiniband/core/umem.c             | 12 ++++++------
 drivers/infiniband/hw/hfi1/user_pages.c    |  6 +++---
 drivers/infiniband/hw/qib/qib_user_pages.c |  4 ++--
 drivers/infiniband/hw/usnic/usnic_uiom.c   |  8 ++++----
 drivers/misc/mic/scif/scif_rma.c           |  6 +++---
 fs/proc/task_mmu.c                         |  2 +-
 include/linux/mm_types.h                   |  2 +-
 kernel/events/core.c                       |  8 ++++----
 kernel/fork.c                              |  2 +-
 mm/debug.c                                 |  3 ++-
 10 files changed, 27 insertions(+), 26 deletions(-)

diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 1efe0a74e06b..678abe1afcba 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -166,13 +166,13 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
 	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 
 	down_write(&mm->mmap_sem);
-	if (check_add_overflow(mm->pinned_vm, npages, &new_pinned) ||
-	    (new_pinned > lock_limit && !capable(CAP_IPC_LOCK))) {
+	new_pinned = atomic64_read(&mm->pinned_vm) + npages;
+	if (new_pinned > lock_limit && !capable(CAP_IPC_LOCK)) {
 		up_write(&mm->mmap_sem);
 		ret = -ENOMEM;
 		goto out;
 	}
-	mm->pinned_vm = new_pinned;
+	atomic64_set(&mm->pinned_vm, new_pinned);
 	up_write(&mm->mmap_sem);
 
 	cur_base = addr & PAGE_MASK;
@@ -234,7 +234,7 @@ struct ib_umem *ib_umem_get(struct ib_udata *udata, unsigned long addr,
 	__ib_umem_release(context->device, umem, 0);
 vma:
 	down_write(&mm->mmap_sem);
-	mm->pinned_vm -= ib_umem_num_pages(umem);
+	atomic64_sub(ib_umem_num_pages(umem), &mm->pinned_vm);
 	up_write(&mm->mmap_sem);
 out:
 	if (vma_list)
@@ -263,7 +263,7 @@ static void ib_umem_release_defer(struct work_struct *work)
 	struct ib_umem *umem = container_of(work, struct ib_umem, work);
 
 	down_write(&umem->owning_mm->mmap_sem);
-	umem->owning_mm->pinned_vm -= ib_umem_num_pages(umem);
+	atomic64_sub(ib_umem_num_pages(umem), &umem->owning_mm->pinned_vm);
 	up_write(&umem->owning_mm->mmap_sem);
 
 	__ib_umem_release_tail(umem);
@@ -302,7 +302,7 @@ void ib_umem_release(struct ib_umem *umem)
 	} else {
 		down_write(&umem->owning_mm->mmap_sem);
 	}
-	umem->owning_mm->pinned_vm -= ib_umem_num_pages(umem);
+	atomic64_sub(ib_umem_num_pages(umem), &umem->owning_mm->pinned_vm);
 	up_write(&umem->owning_mm->mmap_sem);
 
 	__ib_umem_release_tail(umem);
diff --git a/drivers/infiniband/hw/hfi1/user_pages.c b/drivers/infiniband/hw/hfi1/user_pages.c
index e341e6dcc388..40a6e434190f 100644
--- a/drivers/infiniband/hw/hfi1/user_pages.c
+++ b/drivers/infiniband/hw/hfi1/user_pages.c
@@ -92,7 +92,7 @@ bool hfi1_can_pin_pages(struct hfi1_devdata *dd, struct mm_struct *mm,
 	size = DIV_ROUND_UP(size, PAGE_SIZE);
 
 	down_read(&mm->mmap_sem);
-	pinned = mm->pinned_vm;
+	pinned = atomic64_read(&mm->pinned_vm);
 	up_read(&mm->mmap_sem);
 
 	/* First, check the absolute limit against all pinned pages. */
@@ -112,7 +112,7 @@ int hfi1_acquire_user_pages(struct mm_struct *mm, unsigned long vaddr, size_t np
 		return ret;
 
 	down_write(&mm->mmap_sem);
-	mm->pinned_vm += ret;
+	atomic64_add(ret, &mm->pinned_vm);
 	up_write(&mm->mmap_sem);
 
 	return ret;
@@ -131,7 +131,7 @@ void hfi1_release_user_pages(struct mm_struct *mm, struct page **p,
 
 	if (mm) { /* during close after signal, mm can be NULL */
 		down_write(&mm->mmap_sem);
-		mm->pinned_vm -= npages;
+		atomic64_sub(npages, &mm->pinned_vm);
 		up_write(&mm->mmap_sem);
 	}
 }
diff --git a/drivers/infiniband/hw/qib/qib_user_pages.c b/drivers/infiniband/hw/qib/qib_user_pages.c
index 16543d5e80c3..602387bf98e7 100644
--- a/drivers/infiniband/hw/qib/qib_user_pages.c
+++ b/drivers/infiniband/hw/qib/qib_user_pages.c
@@ -75,7 +75,7 @@ static int __qib_get_user_pages(unsigned long start_page, size_t num_pages,
 			goto bail_release;
 	}
 
-	current->mm->pinned_vm += num_pages;
+	atomic64_add(num_pages, &current->mm->pinned_vm);
 
 	ret = 0;
 	goto bail;
@@ -156,7 +156,7 @@ void qib_release_user_pages(struct page **p, size_t num_pages)
 	__qib_release_user_pages(p, num_pages, 1);
 
 	if (current->mm) {
-		current->mm->pinned_vm -= num_pages;
+		atomic64_sub(num_pages, &current->mm->pinned_vm);
 		up_write(&current->mm->mmap_sem);
 	}
 }
diff --git a/drivers/infiniband/hw/usnic/usnic_uiom.c b/drivers/infiniband/hw/usnic/usnic_uiom.c
index ce01a59fccc4..854436a2b437 100644
--- a/drivers/infiniband/hw/usnic/usnic_uiom.c
+++ b/drivers/infiniband/hw/usnic/usnic_uiom.c
@@ -129,7 +129,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
 	uiomr->owning_mm = mm = current->mm;
 	down_write(&mm->mmap_sem);
 
-	locked = npages + current->mm->pinned_vm;
+	locked = npages + atomic64_read(&current->mm->pinned_vm);
 	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 
 	if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
@@ -187,7 +187,7 @@ static int usnic_uiom_get_pages(unsigned long addr, size_t size, int writable,
 	if (ret < 0)
 		usnic_uiom_put_pages(chunk_list, 0);
 	else {
-		mm->pinned_vm = locked;
+		atomic64_set(&mm->pinned_vm, locked);
 		mmgrab(uiomr->owning_mm);
 	}
 
@@ -441,7 +441,7 @@ static void usnic_uiom_release_defer(struct work_struct *work)
 		container_of(work, struct usnic_uiom_reg, work);
 
 	down_write(&uiomr->owning_mm->mmap_sem);
-	uiomr->owning_mm->pinned_vm -= usnic_uiom_num_pages(uiomr);
+	atomic64_sub(usnic_uiom_num_pages(uiomr), &uiomr->owning_mm->pinned_vm);
 	up_write(&uiomr->owning_mm->mmap_sem);
 
 	__usnic_uiom_release_tail(uiomr);
@@ -469,7 +469,7 @@ void usnic_uiom_reg_release(struct usnic_uiom_reg *uiomr,
 	} else {
 		down_write(&uiomr->owning_mm->mmap_sem);
 	}
-	uiomr->owning_mm->pinned_vm -= usnic_uiom_num_pages(uiomr);
+	atomic64_sub(usnic_uiom_num_pages(uiomr), &uiomr->owning_mm->pinned_vm);
 	up_write(&uiomr->owning_mm->mmap_sem);
 
 	__usnic_uiom_release_tail(uiomr);
diff --git a/drivers/misc/mic/scif/scif_rma.c b/drivers/misc/mic/scif/scif_rma.c
index 749321eb91ae..2448368f181e 100644
--- a/drivers/misc/mic/scif/scif_rma.c
+++ b/drivers/misc/mic/scif/scif_rma.c
@@ -285,7 +285,7 @@ __scif_dec_pinned_vm_lock(struct mm_struct *mm,
 	} else {
 		down_write(&mm->mmap_sem);
 	}
-	mm->pinned_vm -= nr_pages;
+	atomic64_sub(nr_pages, &mm->pinned_vm);
 	up_write(&mm->mmap_sem);
 	return 0;
 }
@@ -299,7 +299,7 @@ static inline int __scif_check_inc_pinned_vm(struct mm_struct *mm,
 		return 0;
 
 	locked = nr_pages;
-	locked += mm->pinned_vm;
+	locked += atomic64_read(&mm->pinned_vm);
 	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 	if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
 		dev_err(scif_info.mdev.this_device,
@@ -307,7 +307,7 @@ static inline int __scif_check_inc_pinned_vm(struct mm_struct *mm,
 			locked, lock_limit);
 		return -ENOMEM;
 	}
-	mm->pinned_vm = locked;
+	atomic64_set(&mm->pinned_vm, locked);
 	return 0;
 }
 
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6976e17dba68..640ae8a47c73 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -59,7 +59,7 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
 	SEQ_PUT_DEC("VmPeak:\t", hiwater_vm);
 	SEQ_PUT_DEC(" kB\nVmSize:\t", total_vm);
 	SEQ_PUT_DEC(" kB\nVmLck:\t", mm->locked_vm);
-	SEQ_PUT_DEC(" kB\nVmPin:\t", mm->pinned_vm);
+	SEQ_PUT_DEC(" kB\nVmPin:\t", atomic64_read(&mm->pinned_vm));
 	SEQ_PUT_DEC(" kB\nVmHWM:\t", hiwater_rss);
 	SEQ_PUT_DEC(" kB\nVmRSS:\t", total_rss);
 	SEQ_PUT_DEC(" kB\nRssAnon:\t", anon);
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 6312b02d65ed..0c8be6f9c92d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -404,7 +404,7 @@ struct mm_struct {
 
 		unsigned long total_vm;	   /* Total pages mapped */
 		unsigned long locked_vm;   /* Pages that have PG_mlocked set */
-		unsigned long pinned_vm;   /* Refcount permanently increased */
+		atomic64_t    pinned_vm;   /* Refcount permanently increased */
 		unsigned long data_vm;	   /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
 		unsigned long exec_vm;	   /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
 		unsigned long stack_vm;	   /* VM_STACK */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3cd13a30f732..8df0b77a4687 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5459,7 +5459,7 @@ static void perf_mmap_close(struct vm_area_struct *vma)
 
 		/* now it's safe to free the pages */
 		atomic_long_sub(rb->aux_nr_pages, &mmap_user->locked_vm);
-		vma->vm_mm->pinned_vm -= rb->aux_mmap_locked;
+		atomic64_sub(rb->aux_mmap_locked, &vma->vm_mm->pinned_vm);
 
 		/* this has to be the last one */
 		rb_free_aux(rb);
@@ -5532,7 +5532,7 @@ static void perf_mmap_close(struct vm_area_struct *vma)
 	 */
 
 	atomic_long_sub((size >> PAGE_SHIFT) + 1, &mmap_user->locked_vm);
-	vma->vm_mm->pinned_vm -= mmap_locked;
+	atomic64_sub(mmap_locked, &vma->vm_mm->pinned_vm);
 	free_uid(mmap_user);
 
 out_put:
@@ -5680,7 +5680,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 
 	lock_limit = rlimit(RLIMIT_MEMLOCK);
 	lock_limit >>= PAGE_SHIFT;
-	locked = vma->vm_mm->pinned_vm + extra;
+	locked = atomic64_read(&vma->vm_mm->pinned_vm) + extra;
 
 	if ((locked > lock_limit) && perf_paranoid_tracepoint_raw() &&
 		!capable(CAP_IPC_LOCK)) {
@@ -5721,7 +5721,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 unlock:
 	if (!ret) {
 		atomic_long_add(user_extra, &user->locked_vm);
-		vma->vm_mm->pinned_vm += extra;
+		atomic64_add(extra, &vma->vm_mm->pinned_vm);
 
 		atomic_inc(&event->mmap_count);
 	} else if (rb) {
diff --git a/kernel/fork.c b/kernel/fork.c
index c48e9e244a89..a68de9032ced 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -981,7 +981,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 	mm_pgtables_bytes_init(mm);
 	mm->map_count = 0;
 	mm->locked_vm = 0;
-	mm->pinned_vm = 0;
+	atomic64_set(&mm->pinned_vm, 0);
 	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 	spin_lock_init(&mm->page_table_lock);
 	spin_lock_init(&mm->arg_lock);
diff --git a/mm/debug.c b/mm/debug.c
index 0abb987dad9b..bcf70e365a77 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -166,7 +166,8 @@ void dump_mm(const struct mm_struct *mm)
 		mm_pgtables_bytes(mm),
 		mm->map_count,
 		mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
-		mm->pinned_vm, mm->data_vm, mm->exec_vm, mm->stack_vm,
+		atomic64_read(&mm->pinned_vm),
+		mm->data_vm, mm->exec_vm, mm->stack_vm,
 		mm->start_code, mm->end_code, mm->start_data, mm->end_data,
 		mm->start_brk, mm->brk, mm->start_stack,
 		mm->arg_start, mm->arg_end, mm->env_start, mm->env_end,
-- 
2.16.4