[PATCH] mm: add account_locked_vm utility function
Daniel Jordan
daniel.m.jordan at oracle.com
Sat May 4 06:16:30 AEST 2019
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. Error codes stay the same, so user-visible behavior does too.
Signed-off-by: Daniel Jordan <daniel.m.jordan at oracle.com>
Cc: Alan Tull <atull at kernel.org>
Cc: Alexey Kardashevskiy <aik at ozlabs.ru>
Cc: Alex Williamson <alex.williamson at redhat.com>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Christoph Lameter <cl at linux.com>
Cc: Christophe Leroy <christophe.leroy at c-s.fr>
Cc: Davidlohr Bueso <dave at stgolabs.net>
Cc: Jason Gunthorpe <jgg at mellanox.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Moritz Fischer <mdf at kernel.org>
Cc: Paul Mackerras <paulus at ozlabs.org>
Cc: Steve Sistare <steven.sistare at oracle.com>
Cc: Wu Hao <hao.wu at intel.com>
Cc: linux-mm at kvack.org
Cc: kvm at vger.kernel.org
Cc: kvm-ppc at vger.kernel.org
Cc: linuxppc-dev at lists.ozlabs.org
Cc: linux-fpga at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
---
Based on v5.1-rc7. Tested with the vfio type1 driver. Any feedback
welcome.
Andrew, this one patch replaces these six from [1]:
mm-change-locked_vms-type-from-unsigned-long-to-atomic64_t.patch
vfio-type1-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
vfio-spapr_tce-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
fpga-dlf-afu-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
kvm-book3s-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
powerpc-mmu-drop-mmap_sem-now-that-locked_vm-is-atomic.patch
That series converts locked_vm to an atomic, but on closer inspection causes at
least one accounting race in mremap, and fixing it just for this type
conversion came with too much ugly in the core mm to justify, especially when
the right long-term fix is making these drivers use pinned_vm instead.
Christophe's suggestion of cmpxchg[2] does prevent the races he
mentioned for pinned_vm, but others would still remain. In perf_mmap
and the hfi1 driver, pinned_vm is checked against the rlimit racily and
then later increased when the pinned_vm originally read may have gone
stale. Any fixes for that, that I could think of, seem about as good as
what's there now, so I left it. I have a patch that uses cmpxchg with
pinned_vm if others feel strongly that the aforementioned races should
be fixed.
Daniel
[1] https://lore.kernel.org/linux-mm/20190402204158.27582-1-daniel.m.jordan@oracle.com/
[2] https://lore.kernel.org/linux-mm/964bd5b0-f1e5-7bf0-5c58-18e75c550841@c-s.fr/
arch/powerpc/kvm/book3s_64_vio.c | 44 +++---------------------
arch/powerpc/mm/mmu_context_iommu.c | 41 +++-------------------
drivers/fpga/dfl-afu-dma-region.c | 53 +++--------------------------
drivers/vfio/vfio_iommu_spapr_tce.c | 52 +++++-----------------------
drivers/vfio/vfio_iommu_type1.c | 23 ++++---------
include/linux/mm.h | 19 +++++++++++
mm/util.c | 48 ++++++++++++++++++++++++++
7 files changed, 94 insertions(+), 186 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index f02b04973710..f7d37fa6003a 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(¤t->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(¤t->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,
@@ -277,7 +241,7 @@ 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);
@@ -303,7 +267,7 @@ 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;
@@ -359,7 +323,7 @@ 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/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
index 8330f135294f..9e7001a70570 100644
--- a/arch/powerpc/mm/mmu_context_iommu.c
+++ b/arch/powerpc/mm/mmu_context_iommu.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;
@@ -215,7 +182,7 @@ 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;
}
@@ -315,7 +282,7 @@ 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 e18a786fc943..059438e17193 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(¤t->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(¤t->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 6b64e45a5269..d39a1b830d82 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>
@@ -34,49 +35,13 @@
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)
+static int tce_account_locked_vm(struct mm_struct *mm, unsigned long npages,
+ bool inc)
{
- 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);
+ return account_locked_vm(mm, npages, inc);
}
/*
@@ -336,7 +301,7 @@ 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 = tce_account_locked_vm(container->mm, locked, true);
if (ret)
return ret;
@@ -355,7 +320,7 @@ static void tce_iommu_disable(struct tce_container *container)
container->enabled = false;
BUG_ON(!container->mm);
- decrement_locked_vm(container->mm, container->locked_pages);
+ tce_account_locked_vm(container->mm, container->locked_pages, false);
}
static void *tce_iommu_open(unsigned long arg)
@@ -658,7 +623,8 @@ 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 = tce_account_locked_vm(container->mm, table_size >> PAGE_SHIFT,
+ true);
if (ret)
return ret;
@@ -677,7 +643,7 @@ 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);
+ tce_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 d0f731c9920a..15ac76171ccd 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -273,25 +273,14 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
return -ESRCH; /* process exited */
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)
+ goto out;
- if (!ret)
- mm->locked_vm += npage;
-
- up_write(&mm->mmap_sem);
- }
+ ret = __account_locked_vm(mm, abs(npage), npage > 0, dma->task,
+ dma->lock_cap);
+ up_write(&mm->mmap_sem);
+out:
if (async)
mmput(mm);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6b10c21630f5..7134e55ca23f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1521,6 +1521,25 @@ static inline long get_user_pages_longterm(unsigned long start,
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
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 43a2984bccaa..552302665bc2 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 +347,53 @@ 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;
+ goto out;
+ }
+ }
+ mm->locked_vm = locked_vm + pages;
+ } else {
+ WARN_ON_ONCE(pages > locked_vm);
+ mm->locked_vm = locked_vm - pages;
+ }
+
+out:
+ pr_debug("%s: [%d] %c%lu %lu/%lu%s\n", __func__, task->pid,
+ (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: 37624b58542fb9f2d9a70e6ea006ef8a5f66c30b
--
2.21.0
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