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authorJason Gunthorpe <jgg@mellanox.com>2019-05-23 11:08:28 -0300
committerJason Gunthorpe <jgg@mellanox.com>2019-06-18 12:11:16 -0300
commit47f245985a4f3e270b1e4f28aa49f4c939527981 (patch)
treeba0dcb5d040a33a32c50a9dbad6f467cc65f248d /mm/hmm.c
parent157816f3775f5c4df2c68ef0e3a100ada974aa2e (diff)
downloadlwn-47f245985a4f3e270b1e4f28aa49f4c939527981.tar.gz
lwn-47f245985a4f3e270b1e4f28aa49f4c939527981.zip
mm/hmm: Hold on to the mmget for the lifetime of the range
Range functions like hmm_range_snapshot() and hmm_range_fault() call find_vma, which requires hodling the mmget() and the mmap_sem for the mm. Make this simpler for the callers by holding the mmget() inside the range for the lifetime of the range. Other functions that accept a range should only be called if the range is registered. This has the side effect of directly preventing hmm_release() from happening while a range is registered. That means range->dead cannot be false during the lifetime of the range, so remove dead and hmm_mirror_mm_is_alive() entirely. Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> Reviewed-by: John Hubbard <jhubbard@nvidia.com> Reviewed-by: Ralph Campbell <rcampbell@nvidia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Tested-by: Philip Yang <Philip.Yang@amd.com>
Diffstat (limited to 'mm/hmm.c')
-rw-r--r--mm/hmm.c32
1 files changed, 11 insertions, 21 deletions
diff --git a/mm/hmm.c b/mm/hmm.c
index 73c8af4827fe..1eddda45cefa 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -67,7 +67,6 @@ static struct hmm *hmm_get_or_create(struct mm_struct *mm)
mutex_init(&hmm->lock);
kref_init(&hmm->kref);
hmm->notifiers = 0;
- hmm->dead = false;
hmm->mm = mm;
hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops;
@@ -120,21 +119,16 @@ static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
{
struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
struct hmm_mirror *mirror;
- struct hmm_range *range;
/* Bail out if hmm is in the process of being freed */
if (!kref_get_unless_zero(&hmm->kref))
return;
- /* Report this HMM as dying. */
- hmm->dead = true;
-
- /* Wake-up everyone waiting on any range. */
- mutex_lock(&hmm->lock);
- list_for_each_entry(range, &hmm->ranges, list)
- range->valid = false;
- wake_up_all(&hmm->wq);
- mutex_unlock(&hmm->lock);
+ /*
+ * Since hmm_range_register() holds the mmget() lock hmm_release() is
+ * prevented as long as a range exists.
+ */
+ WARN_ON(!list_empty_careful(&hmm->ranges));
down_write(&hmm->mirrors_sem);
mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
@@ -903,8 +897,8 @@ int hmm_range_register(struct hmm_range *range,
range->start = start;
range->end = end;
- /* Check if hmm_mm_destroy() was call. */
- if (hmm->mm == NULL || hmm->dead)
+ /* Prevent hmm_release() from running while the range is valid */
+ if (!mmget_not_zero(hmm->mm))
return -EFAULT;
/* Initialize range to track CPU page table updates. */
@@ -942,11 +936,12 @@ void hmm_range_unregister(struct hmm_range *range)
return;
mutex_lock(&hmm->lock);
- list_del(&range->list);
+ list_del_init(&range->list);
mutex_unlock(&hmm->lock);
/* Drop reference taken by hmm_range_register() */
range->valid = false;
+ mmput(hmm->mm);
hmm_put(hmm);
range->hmm = NULL;
}
@@ -974,10 +969,7 @@ long hmm_range_snapshot(struct hmm_range *range)
struct vm_area_struct *vma;
struct mm_walk mm_walk;
- /* Check if hmm_mm_destroy() was call. */
- if (hmm->mm == NULL || hmm->dead)
- return -EFAULT;
-
+ lockdep_assert_held(&hmm->mm->mmap_sem);
do {
/* If range is no longer valid force retry. */
if (!range->valid)
@@ -1072,9 +1064,7 @@ long hmm_range_fault(struct hmm_range *range, bool block)
struct mm_walk mm_walk;
int ret;
- /* Check if hmm_mm_destroy() was call. */
- if (hmm->mm == NULL || hmm->dead)
- return -EFAULT;
+ lockdep_assert_held(&hmm->mm->mmap_sem);
do {
/* If range is no longer valid force retry. */