From: Christoph Hellwig <hch@lst.de>
To: "Dan Williams" <dan.j.williams@intel.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Ben Skeggs" <bskeggs@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>,
linux-mm@kvack.org, nouveau@lists.freedesktop.org,
dri-devel@lists.freedesktop.org, linux-nvdimm@lists.01.org,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
John Hubbard <jhubbard@nvidia.com>,
Ralph Campbell <rcampbell@nvidia.com>,
Philip Yang <Philip.Yang@amd.com>
Subject: [PATCH 12/22] mm/hmm: Hold on to the mmget for the lifetime of the range
Date: Mon, 1 Jul 2019 08:20:10 +0200 [thread overview]
Message-ID: <20190701062020.19239-13-hch@lst.de> (raw)
In-Reply-To: <20190701062020.19239-1-hch@lst.de>
From: Jason Gunthorpe <jgg@mellanox.com>
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>
---
include/linux/hmm.h | 26 --------------------------
mm/hmm.c | 32 +++++++++++---------------------
2 files changed, 11 insertions(+), 47 deletions(-)
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 26e7c477490c..bf013e965257 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -82,7 +82,6 @@
* @mirrors_sem: read/write semaphore protecting the mirrors list
* @wq: wait queue for user waiting on a range invalidation
* @notifiers: count of active mmu notifiers
- * @dead: is the mm dead ?
*/
struct hmm {
struct mm_struct *mm;
@@ -95,7 +94,6 @@ struct hmm {
wait_queue_head_t wq;
struct rcu_head rcu;
long notifiers;
- bool dead;
};
/*
@@ -459,30 +457,6 @@ struct hmm_mirror {
int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm);
void hmm_mirror_unregister(struct hmm_mirror *mirror);
-/*
- * hmm_mirror_mm_is_alive() - test if mm is still alive
- * @mirror: the HMM mm mirror for which we want to lock the mmap_sem
- * Return: false if the mm is dead, true otherwise
- *
- * This is an optimization, it will not always accurately return false if the
- * mm is dead; i.e., there can be false negatives (process is being killed but
- * HMM is not yet informed of that). It is only intended to be used to optimize
- * out cases where the driver is about to do something time consuming and it
- * would be better to skip it if the mm is dead.
- */
-static inline bool hmm_mirror_mm_is_alive(struct hmm_mirror *mirror)
-{
- struct mm_struct *mm;
-
- if (!mirror || !mirror->hmm)
- return false;
- mm = READ_ONCE(mirror->hmm->mm);
- if (mirror->hmm->dead || !mm)
- return false;
-
- return true;
-}
-
/*
* Please see Documentation/vm/hmm.rst for how to use the range API.
*/
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. */
--
2.20.1
next prev parent reply other threads:[~2019-07-01 6:21 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 6:19 dev_pagemap related cleanups v4 Christoph Hellwig
2019-07-01 6:19 ` [PATCH 01/22] mm/hmm.c: suppress compilation warnings when CONFIG_HUGETLB_PAGE is not set Christoph Hellwig
2019-07-01 6:20 ` [PATCH 02/22] mm/hmm: update HMM documentation Christoph Hellwig
2019-07-01 6:20 ` [PATCH 03/22] mm/hmm: clean up some coding style and comments Christoph Hellwig
2019-07-01 6:20 ` [PATCH 04/22] mm/hmm: support automatic NUMA balancing Christoph Hellwig
2019-07-01 6:20 ` [PATCH 05/22] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for non-blocking Christoph Hellwig
2019-07-01 6:20 ` [PATCH 06/22] mm/hmm: fix use after free with struct hmm in the mmu notifiers Christoph Hellwig
2019-07-01 6:20 ` [PATCH 07/22] mm/hmm: Use hmm_mirror not mm as an argument for hmm_range_register Christoph Hellwig
2019-07-01 6:20 ` [PATCH 08/22] mm/hmm: Hold a mmgrab from hmm to mm Christoph Hellwig
2019-07-01 6:20 ` [PATCH 09/22] mm/hmm: Simplify hmm_get_or_create and make it reliable Christoph Hellwig
2019-07-01 6:20 ` [PATCH 10/22] mm/hmm: Remove duplicate condition test before wait_event_timeout Christoph Hellwig
2019-07-01 6:20 ` [PATCH 11/22] mm/hmm: Do not use list*_rcu() for hmm->ranges Christoph Hellwig
2019-07-01 6:20 ` Christoph Hellwig [this message]
2019-07-01 6:20 ` [PATCH 13/22] mm/hmm: Use lockdep instead of comments Christoph Hellwig
2019-07-01 6:20 ` [PATCH 14/22] mm/hmm: Remove racy protection against double-unregistration Christoph Hellwig
2019-07-01 6:20 ` [PATCH 15/22] mm/hmm: Poison hmm_range during unregister Christoph Hellwig
2019-07-01 6:20 ` [PATCH 16/22] mm/hmm: Remove confusing comment and logic from hmm_release Christoph Hellwig
2019-07-01 6:20 ` [PATCH 17/22] mm/hmm: Fix error flows in hmm_invalidate_range_start Christoph Hellwig
2019-07-01 6:20 ` [PATCH 18/22] mm: return valid info from hmm_range_unregister Christoph Hellwig
2019-07-03 17:22 ` Ralph Campbell
2019-07-01 6:20 ` [PATCH 19/22] mm: always return EBUSY for invalid ranges in hmm_range_{fault,snapshot} Christoph Hellwig
2019-07-02 21:43 ` Kuehling, Felix
2019-07-03 17:32 ` Ralph Campbell
2019-07-01 6:20 ` [PATCH 20/22] mm: move hmm_vma_fault to nouveau Christoph Hellwig
2019-07-03 17:48 ` Ralph Campbell
2019-07-03 17:50 ` [Nouveau] " Ilia Mirkin
2019-07-03 18:03 ` Jason Gunthorpe
2019-07-03 18:05 ` Christoph Hellwig
2019-07-03 18:13 ` Jason Gunthorpe
2019-07-01 6:20 ` [PATCH 21/22] nouveau: unlock mmap_sem on all errors from nouveau_range_fault Christoph Hellwig
2019-07-01 6:20 ` [PATCH 22/22] mm: remove the legacy hmm_pfn_* APIs Christoph Hellwig
2019-07-03 18:01 ` Jason Gunthorpe
2019-07-03 18:03 ` Christoph Hellwig
2019-07-03 18:15 ` Jason Gunthorpe
2019-07-01 8:25 ` dev_pagemap related cleanups v4 Christoph Hellwig
2019-07-02 18:42 ` Jason Gunthorpe
2019-07-02 22:45 ` Weiny, Ira
2019-07-02 22:47 ` Christoph Hellwig
2019-07-02 23:17 ` Dan Williams
2019-07-03 1:08 ` Jason Gunthorpe
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