[PATCH v2] mm: add account_locked_vm utility function

From: Daniel Jordan
Date: Fri May 24 2019 - 13:55:21 EST

locked_vm accounting is done roughly the same way in five places, so
unify them in a helper. Standardize the debug prints, which vary
slightly, but include the helper's caller to disambiguate between
callsites.

Error codes stay the same, so user-visible behavior does too. The one
exception is that the -EPERM case in tce_account_locked_vm is removed
because Alexey has never seen it triggered.

Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Tested-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
Cc: Alan Tull <atull@xxxxxxxxxx>
Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Moritz Fischer <mdf@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxxx>
Cc: Steve Sistare <steven.sistare@xxxxxxxxxx>
Cc: Wu Hao <hao.wu@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
Cc: kvm-ppc@xxxxxxxxxxxxxxx
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: linux-fpga@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---

Against v5.2-rc1.

v2:
- applied review comments from Alexey
- added _RET_IP_ to debug print to disambiguate callers

arch/powerpc/kvm/book3s_64_vio.c | 44 +++--------------------
arch/powerpc/mm/book3s64/iommu_api.c | 41 +++------------------
drivers/fpga/dfl-afu-dma-region.c | 53 +++------------------------
drivers/vfio/vfio_iommu_spapr_tce.c | 54 +++-------------------------
drivers/vfio/vfio_iommu_type1.c | 17 ++-------
include/linux/mm.h | 19 ++++++++++
mm/util.c | 46 ++++++++++++++++++++++++
7 files changed, 84 insertions(+), 190 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index 66270e07449a..768b645c7edf 100644
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -30,6 +30,7 @@
#include <linux/anon_inodes.h>
#include <linux/iommu.h>
#include <linux/file.h>
+#include <linux/mm.h>

#include <asm/kvm_ppc.h>
#include <asm/kvm_book3s.h>
@@ -56,43 +57,6 @@ static unsigned long kvmppc_stt_pages(unsigned long tce_pages)
return tce_pages + ALIGN(stt_bytes, PAGE_SIZE) / PAGE_SIZE;
}

-static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc)
-{
- long ret = 0;
-
- if (!current || !current->mm)
- return ret; /* process exited */
-
- down_write(&current->mm->mmap_sem);
-
- if (inc) {
- unsigned long locked, lock_limit;
-
- locked = current->mm->locked_vm + stt_pages;
- lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
- ret = -ENOMEM;
- else
- current->mm->locked_vm += stt_pages;
- } else {
- if (WARN_ON_ONCE(stt_pages > current->mm->locked_vm))
- stt_pages = current->mm->locked_vm;
-
- current->mm->locked_vm -= stt_pages;
- }
-
- pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%ld %ld/%ld%s\n", current->pid,
- inc ? '+' : '-',
- stt_pages << PAGE_SHIFT,
- current->mm->locked_vm << PAGE_SHIFT,
- rlimit(RLIMIT_MEMLOCK),
- ret ? " - exceeded" : "");
-
- up_write(&current->mm->mmap_sem);
-
- return ret;
-}
-
static void kvm_spapr_tce_iommu_table_free(struct rcu_head *head)
{
struct kvmppc_spapr_tce_iommu_table *stit = container_of(head,
@@ -302,7 +266,7 @@ static int kvm_spapr_tce_release(struct inode *inode, struct file *filp)

kvm_put_kvm(stt->kvm);

- kvmppc_account_memlimit(
+ account_locked_vm(current->mm,
kvmppc_stt_pages(kvmppc_tce_pages(stt->size)), false);
call_rcu(&stt->rcu, release_spapr_tce_table);

@@ -327,7 +291,7 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
return -EINVAL;

npages = kvmppc_tce_pages(size);
- ret = kvmppc_account_memlimit(kvmppc_stt_pages(npages), true);
+ ret = account_locked_vm(current->mm, kvmppc_stt_pages(npages), true);
if (ret)
return ret;

@@ -373,7 +337,7 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,

kfree(stt);
fail_acct:
- kvmppc_account_memlimit(kvmppc_stt_pages(npages), false);
+ account_locked_vm(current->mm, kvmppc_stt_pages(npages), false);
return ret;
}

diff --git a/arch/powerpc/mm/book3s64/iommu_api.c b/arch/powerpc/mm/book3s64/iommu_api.c
index 5c521f3924a5..18d22eec0ebd 100644
--- a/arch/powerpc/mm/book3s64/iommu_api.c
+++ b/arch/powerpc/mm/book3s64/iommu_api.c
@@ -19,6 +19,7 @@
#include <linux/hugetlb.h>
#include <linux/swap.h>
#include <linux/sizes.h>
+#include <linux/mm.h>
#include <asm/mmu_context.h>
#include <asm/pte-walk.h>
#include <linux/mm_inline.h>
@@ -51,40 +52,6 @@ struct mm_iommu_table_group_mem_t {
u64 dev_hpa; /* Device memory base address */
};

-static long mm_iommu_adjust_locked_vm(struct mm_struct *mm,
- unsigned long npages, bool incr)
-{
- long ret = 0, locked, lock_limit;
-
- if (!npages)
- return 0;
-
- down_write(&mm->mmap_sem);
-
- if (incr) {
- locked = mm->locked_vm + npages;
- lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
- ret = -ENOMEM;
- else
- mm->locked_vm += npages;
- } else {
- if (WARN_ON_ONCE(npages > mm->locked_vm))
- npages = mm->locked_vm;
- mm->locked_vm -= npages;
- }
-
- pr_debug("[%d] RLIMIT_MEMLOCK HASH64 %c%ld %ld/%ld\n",
- current ? current->pid : 0,
- incr ? '+' : '-',
- npages << PAGE_SHIFT,
- mm->locked_vm << PAGE_SHIFT,
- rlimit(RLIMIT_MEMLOCK));
- up_write(&mm->mmap_sem);
-
- return ret;
-}
-
bool mm_iommu_preregistered(struct mm_struct *mm)
{
return !list_empty(&mm->context.iommu_group_mem_list);
@@ -101,7 +68,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
unsigned long entry, chunk;

if (dev_hpa == MM_IOMMU_TABLE_INVALID_HPA) {
- ret = mm_iommu_adjust_locked_vm(mm, entries, true);
+ ret = account_locked_vm(mm, entries, true);
if (ret)
return ret;

@@ -216,7 +183,7 @@ static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
kfree(mem);

unlock_exit:
- mm_iommu_adjust_locked_vm(mm, locked_entries, false);
+ account_locked_vm(mm, locked_entries, false);

return ret;
}
@@ -316,7 +283,7 @@ long mm_iommu_put(struct mm_struct *mm, struct mm_iommu_table_group_mem_t *mem)
unlock_exit:
mutex_unlock(&mem_list_mutex);

- mm_iommu_adjust_locked_vm(mm, unlock_entries, false);
+ account_locked_vm(mm, unlock_entries, false);

return ret;
}
diff --git a/drivers/fpga/dfl-afu-dma-region.c b/drivers/fpga/dfl-afu-dma-region.c
index c438722bf4e1..0a532c602d8f 100644
--- a/drivers/fpga/dfl-afu-dma-region.c
+++ b/drivers/fpga/dfl-afu-dma-region.c
@@ -12,6 +12,7 @@
#include <linux/dma-mapping.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
+#include <linux/mm.h>

#include "dfl-afu.h"

@@ -31,52 +32,6 @@ void afu_dma_region_init(struct dfl_feature_platform_data *pdata)
afu->dma_regions = RB_ROOT;
}

-/**
- * afu_dma_adjust_locked_vm - adjust locked memory
- * @dev: port device
- * @npages: number of pages
- * @incr: increase or decrease locked memory
- *
- * Increase or decrease the locked memory size with npages input.
- *
- * Return 0 on success.
- * Return -ENOMEM if locked memory size is over the limit and no CAP_IPC_LOCK.
- */
-static int afu_dma_adjust_locked_vm(struct device *dev, long npages, bool incr)
-{
- unsigned long locked, lock_limit;
- int ret = 0;
-
- /* the task is exiting. */
- if (!current->mm)
- return 0;
-
- down_write(&current->mm->mmap_sem);
-
- if (incr) {
- locked = current->mm->locked_vm + npages;
- lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
-
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
- ret = -ENOMEM;
- else
- current->mm->locked_vm += npages;
- } else {
- if (WARN_ON_ONCE(npages > current->mm->locked_vm))
- npages = current->mm->locked_vm;
- current->mm->locked_vm -= npages;
- }
-
- dev_dbg(dev, "[%d] RLIMIT_MEMLOCK %c%ld %ld/%ld%s\n", current->pid,
- incr ? '+' : '-', npages << PAGE_SHIFT,
- current->mm->locked_vm << PAGE_SHIFT, rlimit(RLIMIT_MEMLOCK),
- ret ? "- exceeded" : "");
-
- up_write(&current->mm->mmap_sem);
-
- return ret;
-}
-
/**
* afu_dma_pin_pages - pin pages of given dma memory region
* @pdata: feature device platform data
@@ -92,7 +47,7 @@ static int afu_dma_pin_pages(struct dfl_feature_platform_data *pdata,
struct device *dev = &pdata->dev->dev;
int ret, pinned;

- ret = afu_dma_adjust_locked_vm(dev, npages, true);
+ ret = account_locked_vm(current->mm, npages, true);
if (ret)
return ret;

@@ -121,7 +76,7 @@ static int afu_dma_pin_pages(struct dfl_feature_platform_data *pdata,
free_pages:
kfree(region->pages);
unlock_vm:
- afu_dma_adjust_locked_vm(dev, npages, false);
+ account_locked_vm(current->mm, npages, false);
return ret;
}

@@ -141,7 +96,7 @@ static void afu_dma_unpin_pages(struct dfl_feature_platform_data *pdata,

put_all_pages(region->pages, npages);
kfree(region->pages);
- afu_dma_adjust_locked_vm(dev, npages, false);
+ account_locked_vm(current->mm, npages, false);

dev_dbg(dev, "%ld pages unpinned\n", npages);
}
diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 40ddc0c5f677..d06e8e291924 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -22,6 +22,7 @@
#include <linux/vmalloc.h>
#include <linux/sched/mm.h>
#include <linux/sched/signal.h>
+#include <linux/mm.h>

#include <asm/iommu.h>
#include <asm/tce.h>
@@ -34,51 +35,6 @@
static void tce_iommu_detach_group(void *iommu_data,
struct iommu_group *iommu_group);

-static long try_increment_locked_vm(struct mm_struct *mm, long npages)
-{
- long ret = 0, locked, lock_limit;
-
- if (WARN_ON_ONCE(!mm))
- return -EPERM;
-
- if (!npages)
- return 0;
-
- down_write(&mm->mmap_sem);
- locked = mm->locked_vm + npages;
- lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
- ret = -ENOMEM;
- else
- mm->locked_vm += npages;
-
- pr_debug("[%d] RLIMIT_MEMLOCK +%ld %ld/%ld%s\n", current->pid,
- npages << PAGE_SHIFT,
- mm->locked_vm << PAGE_SHIFT,
- rlimit(RLIMIT_MEMLOCK),
- ret ? " - exceeded" : "");
-
- up_write(&mm->mmap_sem);
-
- return ret;
-}
-
-static void decrement_locked_vm(struct mm_struct *mm, long npages)
-{
- if (!mm || !npages)
- return;
-
- down_write(&mm->mmap_sem);
- if (WARN_ON_ONCE(npages > mm->locked_vm))
- npages = mm->locked_vm;
- mm->locked_vm -= npages;
- pr_debug("[%d] RLIMIT_MEMLOCK -%ld %ld/%ld\n", current->pid,
- npages << PAGE_SHIFT,
- mm->locked_vm << PAGE_SHIFT,
- rlimit(RLIMIT_MEMLOCK));
- up_write(&mm->mmap_sem);
-}
-
/*
* VFIO IOMMU fd for SPAPR_TCE IOMMU implementation
*
@@ -336,7 +292,7 @@ static int tce_iommu_enable(struct tce_container *container)
return ret;

locked = table_group->tce32_size >> PAGE_SHIFT;
- ret = try_increment_locked_vm(container->mm, locked);
+ ret = account_locked_vm(container->mm, locked, true);
if (ret)
return ret;

@@ -355,7 +311,7 @@ static void tce_iommu_disable(struct tce_container *container)
container->enabled = false;

BUG_ON(!container->mm);
- decrement_locked_vm(container->mm, container->locked_pages);
+ account_locked_vm(container->mm, container->locked_pages, false);
}

static void *tce_iommu_open(unsigned long arg)
@@ -659,7 +615,7 @@ static long tce_iommu_create_table(struct tce_container *container,
if (!table_size)
return -EINVAL;

- ret = try_increment_locked_vm(container->mm, table_size >> PAGE_SHIFT);
+ ret = account_locked_vm(container->mm, table_size >> PAGE_SHIFT, true);
if (ret)
return ret;

@@ -678,7 +634,7 @@ static void tce_iommu_free_table(struct tce_container *container,
unsigned long pages = tbl->it_allocated_size >> PAGE_SHIFT;

iommu_tce_table_put(tbl);
- decrement_locked_vm(container->mm, pages);
+ account_locked_vm(container->mm, pages, false);
}

static long tce_iommu_create_window(struct tce_container *container,
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 3ddc375e7063..bf449ace1676 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -275,21 +275,8 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)

ret = down_write_killable(&mm->mmap_sem);
if (!ret) {
- if (npage > 0) {
- if (!dma->lock_cap) {
- unsigned long limit;
-
- limit = task_rlimit(dma->task,
- RLIMIT_MEMLOCK) >> PAGE_SHIFT;
-
- if (mm->locked_vm + npage > limit)
- ret = -ENOMEM;
- }
- }
-
- if (!ret)
- mm->locked_vm += npage;
-
+ ret = __account_locked_vm(mm, abs(npage), npage > 0, dma->task,
+ dma->lock_cap);
up_write(&mm->mmap_sem);
}

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0e8834ac32b7..72c1034d2ec7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1564,6 +1564,25 @@ long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
int get_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages);

+int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
+ struct task_struct *task, bool bypass_rlim);
+
+static inline int account_locked_vm(struct mm_struct *mm, unsigned long pages,
+ bool inc)
+{
+ int ret;
+
+ if (pages == 0 || !mm)
+ return 0;
+
+ down_write(&mm->mmap_sem);
+ ret = __account_locked_vm(mm, pages, inc, current,
+ capable(CAP_IPC_LOCK));
+ up_write(&mm->mmap_sem);
+
+ return ret;
+}
+
/* Container for pinned pfns / pages */
struct frame_vector {
unsigned int nr_allocated; /* Number of frames we have space for */
diff --git a/mm/util.c b/mm/util.c
index e2e4f8c3fa12..bd3bdf16a084 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -6,6 +6,7 @@
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
+#include <linux/sched/signal.h>
#include <linux/sched/task_stack.h>
#include <linux/security.h>
#include <linux/swap.h>
@@ -346,6 +347,51 @@ int __weak get_user_pages_fast(unsigned long start,
}
EXPORT_SYMBOL_GPL(get_user_pages_fast);

+/**
+ * __account_locked_vm - account locked pages to an mm's locked_vm
+ * @mm: mm to account against, may be NULL
+ * @pages: number of pages to account
+ * @inc: %true if @pages should be considered positive, %false if not
+ * @task: task used to check RLIMIT_MEMLOCK
+ * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
+ *
+ * Assumes @task and @mm are valid (i.e. at least one reference on each), and
+ * that mmap_sem is held as writer.
+ *
+ * Return:
+ * * 0 on success
+ * * 0 if @mm is NULL (can happen for example if the task is exiting)
+ * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
+ */
+int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
+ struct task_struct *task, bool bypass_rlim)
+{
+ unsigned long locked_vm, limit;
+ int ret = 0;
+
+ locked_vm = mm->locked_vm;
+ if (inc) {
+ if (!bypass_rlim) {
+ limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+ if (locked_vm + pages > limit)
+ ret = -ENOMEM;
+ }
+ if (!ret)
+ mm->locked_vm = locked_vm + pages;
+ } else {
+ WARN_ON_ONCE(pages > locked_vm);
+ mm->locked_vm = locked_vm - pages;
+ }
+
+ pr_debug("%s: [%d] caller %ps %c%lu %lu/%lu%s\n", __func__, task->pid,
+ (void *)_RET_IP_, (inc) ? '+' : '-', pages << PAGE_SHIFT,
+ locked_vm << PAGE_SHIFT, task_rlimit(task, RLIMIT_MEMLOCK),
+ ret ? " - exceeded" : "");
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(__account_locked_vm);
+
unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
unsigned long len, unsigned long prot,
unsigned long flag, unsigned long pgoff)

base-commit: a188339ca5a396acc588e5851ed7e19f66b0ebd9
--
2.21.0