On Mon 07-10-13 19:26:04, Jan Kara wrote:
> On Mon 07-10-13 15:38:24, Marciniszyn, Mike wrote:
> > > > This patch and the sibling ipath patch will nominally take the mmap_sem
> > > > twice where the old routine only took it once. This is a performance
> > > > issue.
> > > It will take mmap_sem only once during normal operation. Only if
> > > get_user_pages_unlocked() fail, we have to take mmap_sem again to undo
> > > the change of mm->pinned_vm.
> > >
> > > > Is the intent here to deprecate get_user_pages()?
> >
> > The old code looked like:
> > __qib_get_user_pages()
> > (broken) ulimit test
> > for (...)
> > get_user_pages()
> >
> > qib_get_user_pages()
> > mmap_sem lock
> > __qib_get_user_pages()
> > mmap_sem() unlock
> >
> > The new code is:
> >
> > get_user_pages_unlocked()
> > mmap_sem lock
> > get_user_pages()
> > mmap_sem unlock
> >
> > qib_get_user_pages()
> > mmap_sem lock
> > ulimit test and locked pages maintenance
> > mmap_sem unlock
> > for (...)
> > get_user_pages_unlocked()
> >
> > I count an additional pair of mmap_sem transactions in the normal case.
> Ah, sorry, you are right.
>
> > > > Could the lock limit test be pushed into another version of the
> > > > wrapper so that there is only one set of mmap_sem transactions?
> > > I'm sorry, I don't understand what you mean here...
> > >
> >
> > This is what I had in mind:
> >
> > get_user_pages_ulimit_unlocked()
> > mmap_sem lock
> > ulimit test and locked pages maintenance (from qib/ipath)
> > for (...)
> > get_user_pages_unlocked()
> > mmap_sem unlock
> >
> > qib_get_user_pages()
> > get_user_pages_ulimit_unlocked()
> >
> > This really pushes the code into a new wrapper common to ipath/qib and
> > any others that might want to combine locking with ulimit enforcement.
> We could do that but frankly, I'd rather change ulimit enforcement to not
> require mmap_sem and use atomic counter instead. I'll see what I can do.
OK, so something like the attached patch (compile tested only). What do
you think? I'm just not 100% sure removing mmap_sem surrounding stuff like
__ipath_release_user_pages() is safe. I don't see a reason why it shouldn't
be - we have references to the pages and we only mark them dirty and put the
reference - but maybe I miss something subtle...
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
>From 44fe90e8303b293370f077ae665d6e43846cf277 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Tue, 8 Oct 2013 14:16:24 +0200
Subject: [PATCH] mm: Switch mm->pinned_vm to atomic_long_t
Currently updates to mm->pinned_vm were protected by mmap_sem.
kernel/events/core.c actually held it only for reading so that may have
been racy. The only other user - Infiniband - used mmap_sem for writing
but it caused quite some complications to it.
So switch mm->pinned_vm and convert all the places using it. This allows
quite some simplifications to Infiniband code and it now doesn't have to
care about mmap_sem at all.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
drivers/infiniband/core/umem.c | 56 +++------------------
drivers/infiniband/core/uverbs_cmd.c | 1 -
drivers/infiniband/core/uverbs_main.c | 2 -
drivers/infiniband/hw/ipath/ipath_file_ops.c | 2 +-
drivers/infiniband/hw/ipath/ipath_kernel.h | 1 -
drivers/infiniband/hw/ipath/ipath_user_pages.c | 70 +++-----------------------
drivers/infiniband/hw/qib/qib_user_pages.c | 20 ++------
fs/proc/task_mmu.c | 2 +-
include/linux/mm_types.h | 2 +-
include/rdma/ib_umem.h | 3 --
include/rdma/ib_verbs.h | 1 -
kernel/events/core.c | 13 +++--
12 files changed, 29 insertions(+), 144 deletions(-)
diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 0640a89021a9..294d2e468177 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -80,6 +80,7 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
{
struct ib_umem *umem;
struct page **page_list;
+ struct mm_struct *mm = current->mm;
struct ib_umem_chunk *chunk;
unsigned long locked;
unsigned long lock_limit;
@@ -126,20 +127,13 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
npages = PAGE_ALIGN(size + umem->offset) >> PAGE_SHIFT;
- down_write(¤t->mm->mmap_sem);
-
lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
locked = npages;
- if (npages + current->mm->pinned_vm > lock_limit &&
+ if (atomic_long_add_return(&mm->pinned_vm, npages) > lock_limit &&
!capable(CAP_IPC_LOCK)) {
- up_write(¤t->mm->mmap_sem);
- kfree(umem);
- free_page((unsigned long) page_list);
- return ERR_PTR(-ENOMEM);
+ ret = -ENOMEM;
+ goto out;
}
- current->mm->pinned_vm += npages;
-
- up_write(¤t->mm->mmap_sem);
cur_base = addr & PAGE_MASK;
@@ -201,9 +195,7 @@ out:
if (ret < 0) {
__ib_umem_release(context->device, umem, 0);
kfree(umem);
- down_write(¤t->mm->mmap_sem);
- current->mm->pinned_vm -= locked;
- up_write(¤t->mm->mmap_sem);
+ atomic_long_sub(&mm->pinned_vm, locked);
}
free_page((unsigned long) page_list);
@@ -211,17 +203,6 @@ out:
}
EXPORT_SYMBOL(ib_umem_get);
-static void ib_umem_account(struct work_struct *work)
-{
- struct ib_umem *umem = container_of(work, struct ib_umem, work);
-
- down_write(&umem->mm->mmap_sem);
- umem->mm->pinned_vm -= umem->diff;
- up_write(&umem->mm->mmap_sem);
- mmput(umem->mm);
- kfree(umem);
-}
-
/**
* ib_umem_release - release memory pinned with ib_umem_get
* @umem: umem struct to release
@@ -234,37 +215,14 @@ void ib_umem_release(struct ib_umem *umem)
__ib_umem_release(umem->context->device, umem, 1);
- mm = get_task_mm(current);
+ mm = current->mm;
if (!mm) {
kfree(umem);
return;
}
diff = PAGE_ALIGN(umem->length + umem->offset) >> PAGE_SHIFT;
-
- /*
- * We may be called with the mm's mmap_sem already held. This
- * can happen when a userspace munmap() is the call that drops
- * the last reference to our file and calls our release
- * method. If there are memory regions to destroy, we'll end
- * up here and not be able to take the mmap_sem. In that case
- * we defer the vm_locked accounting to the system workqueue.
- */
- if (context->closing) {
- if (!down_write_trylock(&mm->mmap_sem)) {
- INIT_WORK(&umem->work, ib_umem_account);
- umem->mm = mm;
- umem->diff = diff;
-
- queue_work(ib_wq, &umem->work);
- return;
- }
- } else
- down_write(&mm->mmap_sem);
-
- current->mm->pinned_vm -= diff;
- up_write(&mm->mmap_sem);
- mmput(mm);
+ atomic_long_sub(&mm->pinned_vm, diff);
kfree(umem);
}
EXPORT_SYMBOL(ib_umem_release);
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index f2b81b9ee0d6..16381c6eae77 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -332,7 +332,6 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
INIT_LIST_HEAD(&ucontext->ah_list);
INIT_LIST_HEAD(&ucontext->xrcd_list);
INIT_LIST_HEAD(&ucontext->rule_list);
- ucontext->closing = 0;
resp.num_comp_vectors = file->device->num_comp_vectors;
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index 75ad86c4abf8..8fdc9ca62c27 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -196,8 +196,6 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
if (!context)
return 0;
- context->closing = 1;
-
list_for_each_entry_safe(uobj, tmp, &context->ah_list, list) {
struct ib_ah *ah = uobj->object;
diff --git a/drivers/infiniband/hw/ipath/ipath_file_ops.c b/drivers/infiniband/hw/ipath/ipath_file_ops.c
index 6d7f453b4d05..f219f15ad1cf 100644
--- a/drivers/infiniband/hw/ipath/ipath_file_ops.c
+++ b/drivers/infiniband/hw/ipath/ipath_file_ops.c
@@ -2025,7 +2025,7 @@ static void unlock_expected_tids(struct ipath_portdata *pd)
dd->ipath_pageshadow[i] = NULL;
pci_unmap_page(dd->pcidev, dd->ipath_physshadow[i],
PAGE_SIZE, PCI_DMA_FROMDEVICE);
- ipath_release_user_pages_on_close(&ps, 1);
+ ipath_release_user_pages(&ps, 1);
cnt++;
ipath_stats.sps_pageunlocks++;
}
diff --git a/drivers/infiniband/hw/ipath/ipath_kernel.h b/drivers/infiniband/hw/ipath/ipath_kernel.h
index 6559af60bffd..afc2f868541b 100644
--- a/drivers/infiniband/hw/ipath/ipath_kernel.h
+++ b/drivers/infiniband/hw/ipath/ipath_kernel.h
@@ -1083,7 +1083,6 @@ static inline void ipath_sdma_desc_unreserve(struct ipath_devdata *dd, u16 cnt)
int ipath_get_user_pages(unsigned long, size_t, struct page **);
void ipath_release_user_pages(struct page **, size_t);
-void ipath_release_user_pages_on_close(struct page **, size_t);
int ipath_eeprom_read(struct ipath_devdata *, u8, void *, int);
int ipath_eeprom_write(struct ipath_devdata *, u8, const void *, int);
int ipath_tempsense_read(struct ipath_devdata *, u8 regnum);
diff --git a/drivers/infiniband/hw/ipath/ipath_user_pages.c b/drivers/infiniband/hw/ipath/ipath_user_pages.c
index a89af9654112..8081e76fa72c 100644
--- a/drivers/infiniband/hw/ipath/ipath_user_pages.c
+++ b/drivers/infiniband/hw/ipath/ipath_user_pages.c
@@ -68,26 +68,22 @@ int ipath_get_user_pages(unsigned long start_page, size_t num_pages,
struct page **p)
{
unsigned long lock_limit;
+ struct mm_struct *mm = current->mm;
size_t got;
int ret;
- down_write(¤t->mm->mmap_sem);
lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
-
- if (current->mm->pinned_vm + num_pages > lock_limit &&
+ if (atomic_long_add_return(&mm->pinned_vm, num_pages) > lock_limit &&
!capable(CAP_IPC_LOCK)) {
- up_write(¤t->mm->mmap_sem);
ret = -ENOMEM;
- goto bail;
+ goto bail_sub;
}
- current->mm->pinned_vm += num_pages;
- up_write(¤t->mm->mmap_sem);
ipath_cdbg(VERBOSE, "pin %lx pages from vaddr %lx\n",
(unsigned long) num_pages, start_page);
for (got = 0; got < num_pages; got += ret) {
- ret = get_user_pages_unlocked(current, current->mm,
+ ret = get_user_pages_unlocked(current, mm,
start_page + got * PAGE_SIZE,
num_pages - got, 1, 1,
p + got);
@@ -101,9 +97,8 @@ int ipath_get_user_pages(unsigned long start_page, size_t num_pages,
bail_release:
__ipath_release_user_pages(p, got, 0);
- down_write(¤t->mm->mmap_sem);
- current->mm->pinned_vm -= num_pages;
- up_write(¤t->mm->mmap_sem);
+bail_sub:
+ atomic_long_sub(&mm->pinned_vm, num_pages);
bail:
return ret;
}
@@ -166,56 +161,7 @@ dma_addr_t ipath_map_single(struct pci_dev *hwdev, void *ptr, size_t size,
void ipath_release_user_pages(struct page **p, size_t num_pages)
{
- down_write(¤t->mm->mmap_sem);
-
- __ipath_release_user_pages(p, num_pages, 1);
-
- current->mm->pinned_vm -= num_pages;
-
- up_write(¤t->mm->mmap_sem);
-}
-
-struct ipath_user_pages_work {
- struct work_struct work;
- struct mm_struct *mm;
- unsigned long num_pages;
-};
-
-static void user_pages_account(struct work_struct *_work)
-{
- struct ipath_user_pages_work *work =
- container_of(_work, struct ipath_user_pages_work, work);
-
- down_write(&work->mm->mmap_sem);
- work->mm->pinned_vm -= work->num_pages;
- up_write(&work->mm->mmap_sem);
- mmput(work->mm);
- kfree(work);
-}
-
-void ipath_release_user_pages_on_close(struct page **p, size_t num_pages)
-{
- struct ipath_user_pages_work *work;
- struct mm_struct *mm;
-
__ipath_release_user_pages(p, num_pages, 1);
-
- mm = get_task_mm(current);
- if (!mm)
- return;
-
- work = kmalloc(sizeof(*work), GFP_KERNEL);
- if (!work)
- goto bail_mm;
-
- INIT_WORK(&work->work, user_pages_account);
- work->mm = mm;
- work->num_pages = num_pages;
-
- queue_work(ib_wq, &work->work);
- return;
-
-bail_mm:
- mmput(mm);
- return;
+ if (current->mm)
+ atomic_long_sub(¤t->mm->pinned_vm, num_pages);
}
diff --git a/drivers/infiniband/hw/qib/qib_user_pages.c b/drivers/infiniband/hw/qib/qib_user_pages.c
index 57ce83c2d1d9..049ab8db5f32 100644
--- a/drivers/infiniband/hw/qib/qib_user_pages.c
+++ b/drivers/infiniband/hw/qib/qib_user_pages.c
@@ -68,16 +68,13 @@ int qib_get_user_pages(unsigned long start_page, size_t num_pages,
int ret;
struct mm_struct *mm = current->mm;
- down_write(&mm->mmap_sem);
lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
- if (mm->pinned_vm + num_pages > lock_limit && !capable(CAP_IPC_LOCK)) {
- up_write(&mm->mmap_sem);
+ if (atomic_long_add_return(&mm->pinned_vm, num_pages) > lock_limit &&
+ !capable(CAP_IPC_LOCK)) {
ret = -ENOMEM;
goto bail;
}
- mm->pinned_vm += num_pages;
- up_write(&mm->mmap_sem);
for (got = 0; got < num_pages; got += ret) {
ret = get_user_pages_unlocked(current, mm,
@@ -94,9 +91,7 @@ int qib_get_user_pages(unsigned long start_page, size_t num_pages,
bail_release:
__qib_release_user_pages(p, got, 0);
- down_write(&mm->mmap_sem);
- mm->pinned_vm -= num_pages;
- up_write(&mm->mmap_sem);
+ atomic_long_sub(&mm->pinned_vm, num_pages);
bail:
return ret;
}
@@ -135,13 +130,8 @@ dma_addr_t qib_map_page(struct pci_dev *hwdev, struct page *page,
void qib_release_user_pages(struct page **p, size_t num_pages)
{
- if (current->mm) /* during close after signal, mm can be NULL */
- down_write(¤t->mm->mmap_sem);
-
__qib_release_user_pages(p, num_pages, 1);
- if (current->mm) {
- current->mm->pinned_vm -= num_pages;
- up_write(¤t->mm->mmap_sem);
- }
+ if (current->mm)
+ atomic_long_sub(¤t->mm->pinned_vm, num_pages);
}
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7366e9d63cee..9123bfef1dea 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -57,7 +57,7 @@ void task_mem(struct seq_file *m, struct mm_struct *mm)
hiwater_vm << (PAGE_SHIFT-10),
total_vm << (PAGE_SHIFT-10),
mm->locked_vm << (PAGE_SHIFT-10),
- mm->pinned_vm << (PAGE_SHIFT-10),
+ atomic_long_read(&mm->pinned_vm) << (PAGE_SHIFT-10),
hiwater_rss << (PAGE_SHIFT-10),
total_rss << (PAGE_SHIFT-10),
data << (PAGE_SHIFT-10),
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index d9851eeb6e1d..f2bf72a86b70 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -355,7 +355,7 @@ 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 */
+ atomic_long_t pinned_vm; /* Refcount permanently increased */
unsigned long shared_vm; /* Shared pages (files) */
unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE */
unsigned long stack_vm; /* VM_GROWSUP/DOWN */
diff --git a/include/rdma/ib_umem.h b/include/rdma/ib_umem.h
index 9ee0d2e51b16..2dbbd2c56074 100644
--- a/include/rdma/ib_umem.h
+++ b/include/rdma/ib_umem.h
@@ -47,9 +47,6 @@ struct ib_umem {
int writable;
int hugetlb;
struct list_head chunk_list;
- struct work_struct work;
- struct mm_struct *mm;
- unsigned long diff;
};
struct ib_umem_chunk {
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index e393171e2fac..bce6d2b91ec7 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -961,7 +961,6 @@ struct ib_ucontext {
struct list_head ah_list;
struct list_head xrcd_list;
struct list_head rule_list;
- int closing;
};
struct ib_uobject {
diff --git a/kernel/events/core.c b/kernel/events/core.c
index dd236b66ca3a..80d2ba7bd51c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3922,7 +3922,7 @@ again:
*/
atomic_long_sub((size >> PAGE_SHIFT) + 1, &mmap_user->locked_vm);
- vma->vm_mm->pinned_vm -= mmap_locked;
+ atomic_long_sub(&vma->vm_mm->pinned_vm, mmap_locked);
free_uid(mmap_user);
ring_buffer_put(rb); /* could be last */
@@ -3944,7 +3944,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
struct ring_buffer *rb;
unsigned long vma_size;
unsigned long nr_pages;
- long user_extra, extra;
+ long user_extra, extra = 0;
int ret = 0, flags = 0;
/*
@@ -4006,16 +4006,14 @@ again:
user_locked = atomic_long_read(&user->locked_vm) + user_extra;
- extra = 0;
if (user_locked > user_lock_limit)
extra = user_locked - user_lock_limit;
lock_limit = rlimit(RLIMIT_MEMLOCK);
lock_limit >>= PAGE_SHIFT;
- locked = vma->vm_mm->pinned_vm + extra;
- if ((locked > lock_limit) && perf_paranoid_tracepoint_raw() &&
- !capable(CAP_IPC_LOCK)) {
+ if (atomic_long_add_return(&vma->vm_mm->pinned_vm, extra) > lock_limit &&
+ perf_paranoid_tracepoint_raw() && !capable(CAP_IPC_LOCK)) {
ret = -EPERM;
goto unlock;
}
@@ -4039,7 +4037,6 @@ again:
rb->mmap_user = get_current_user();
atomic_long_add(user_extra, &user->locked_vm);
- vma->vm_mm->pinned_vm += extra;
ring_buffer_attach(event, rb);
rcu_assign_pointer(event->rb, rb);
@@ -4049,6 +4046,8 @@ again:
unlock:
if (!ret)
atomic_inc(&event->mmap_count);
+ else if (extra)
+ atomic_long_sub(&vma->vm_mm->pinned_vm, extra);
mutex_unlock(&event->mmap_mutex);
/*
--
1.8.1.4