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[Xen-devel] [PATCH v3 13/14] mm/hmm: remove hmm_mirror and related



From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>

The only two users of this are now converted to use mmu_interval_notifier,
delete all the code and update hmm.rst.

Reviewed-by: Jérôme Glisse <jglisse@xxxxxxxxxx>
Tested-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
---
 Documentation/vm/hmm.rst | 105 ++++-----------
 include/linux/hmm.h      | 183 +------------------------
 mm/Kconfig               |   1 -
 mm/hmm.c                 | 285 ++-------------------------------------
 4 files changed, 34 insertions(+), 540 deletions(-)

diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
index 0a5960beccf76d..893a8ba0e9fefb 100644
--- a/Documentation/vm/hmm.rst
+++ b/Documentation/vm/hmm.rst
@@ -147,49 +147,16 @@ Address space mirroring implementation and API
 Address space mirroring's main objective is to allow duplication of a range of
 CPU page table into a device page table; HMM helps keep both synchronized. A
 device driver that wants to mirror a process address space must start with the
-registration of an hmm_mirror struct::
-
- int hmm_mirror_register(struct hmm_mirror *mirror,
-                         struct mm_struct *mm);
-
-The mirror struct has a set of callbacks that are used
-to propagate CPU page tables::
-
- struct hmm_mirror_ops {
-     /* release() - release hmm_mirror
-      *
-      * @mirror: pointer to struct hmm_mirror
-      *
-      * This is called when the mm_struct is being released.  The callback
-      * must ensure that all access to any pages obtained from this mirror
-      * is halted before the callback returns. All future access should
-      * fault.
-      */
-     void (*release)(struct hmm_mirror *mirror);
-
-     /* sync_cpu_device_pagetables() - synchronize page tables
-      *
-      * @mirror: pointer to struct hmm_mirror
-      * @update: update information (see struct mmu_notifier_range)
-      * Return: -EAGAIN if update.blockable false and callback need to
-      *         block, 0 otherwise.
-      *
-      * This callback ultimately originates from mmu_notifiers when the CPU
-      * page table is updated. The device driver must update its page table
-      * in response to this callback. The update argument tells what action
-      * to perform.
-      *
-      * The device driver must not return from this callback until the device
-      * page tables are completely updated (TLBs flushed, etc); this is a
-      * synchronous call.
-      */
-     int (*sync_cpu_device_pagetables)(struct hmm_mirror *mirror,
-                                       const struct hmm_update *update);
- };
-
-The device driver must perform the update action to the range (mark range
-read only, or fully unmap, etc.). The device must complete the update before
-the driver callback returns.
+registration of a mmu_interval_notifier::
+
+ mni->ops = &driver_ops;
+ int mmu_interval_notifier_insert(struct mmu_interval_notifier *mni,
+                                 unsigned long start, unsigned long length,
+                                 struct mm_struct *mm);
+
+During the driver_ops->invalidate() callback the device driver must perform
+the update action to the range (mark range read only, or fully unmap,
+etc.). The device must complete the update before the driver callback returns.
 
 When the device driver wants to populate a range of virtual addresses, it can
 use::
@@ -216,70 +183,46 @@ The usage pattern is::
       struct hmm_range range;
       ...
 
+      range.notifier = &mni;
       range.start = ...;
       range.end = ...;
       range.pfns = ...;
       range.flags = ...;
       range.values = ...;
       range.pfn_shift = ...;
-      hmm_range_register(&range, mirror);
 
-      /*
-       * Just wait for range to be valid, safe to ignore return value as we
-       * will use the return value of hmm_range_fault() below under the
-       * mmap_sem to ascertain the validity of the range.
-       */
-      hmm_range_wait_until_valid(&range, TIMEOUT_IN_MSEC);
+      if (!mmget_not_zero(mni->notifier.mm))
+          return -EFAULT;
 
  again:
+      range.notifier_seq = mmu_interval_read_begin(&mni);
       down_read(&mm->mmap_sem);
       ret = hmm_range_fault(&range, HMM_RANGE_SNAPSHOT);
       if (ret) {
           up_read(&mm->mmap_sem);
-          if (ret == -EBUSY) {
-            /*
-             * No need to check hmm_range_wait_until_valid() return value
-             * on retry we will get proper error with hmm_range_fault()
-             */
-            hmm_range_wait_until_valid(&range, TIMEOUT_IN_MSEC);
-            goto again;
-          }
-          hmm_range_unregister(&range);
+          if (ret == -EBUSY)
+                 goto again;
           return ret;
       }
+      up_read(&mm->mmap_sem);
+
       take_lock(driver->update);
-      if (!hmm_range_valid(&range)) {
+      if (mmu_interval_read_retry(&ni, range.notifier_seq) {
           release_lock(driver->update);
-          up_read(&mm->mmap_sem);
           goto again;
       }
 
-      // Use pfns array content to update device page table
+      /* Use pfns array content to update device page table,
+       * under the update lock */
 
-      hmm_range_unregister(&range);
       release_lock(driver->update);
-      up_read(&mm->mmap_sem);
       return 0;
  }
 
 The driver->update lock is the same lock that the driver takes inside its
-sync_cpu_device_pagetables() callback. That lock must be held before calling
-hmm_range_valid() to avoid any race with a concurrent CPU page table update.
-
-HMM implements all this on top of the mmu_notifier API because we wanted a
-simpler API and also to be able to perform optimizations latter on like doing
-concurrent device updates in multi-devices scenario.
-
-HMM also serves as an impedance mismatch between how CPU page table updates
-are done (by CPU write to the page table and TLB flushes) and how devices
-update their own page table. Device updates are a multi-step process. First,
-appropriate commands are written to a buffer, then this buffer is scheduled for
-execution on the device. It is only once the device has executed commands in
-the buffer that the update is done. Creating and scheduling the update command
-buffer can happen concurrently for multiple devices. Waiting for each device to
-report commands as executed is serialized (there is no point in doing this
-concurrently).
-
+invalidate() callback. That lock must be held before calling
+mmu_interval_read_retry() to avoid any race with a concurrent CPU page table
+update.
 
 Leverage default_flags and pfn_flags_mask
 =========================================
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index cb69bf10dc788c..1225b3c87aba05 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -68,29 +68,6 @@
 #include <linux/completion.h>
 #include <linux/mmu_notifier.h>
 
-
-/*
- * struct hmm - HMM per mm struct
- *
- * @mm: mm struct this HMM struct is bound to
- * @lock: lock protecting ranges list
- * @ranges: list of range being snapshotted
- * @mirrors: list of mirrors for this mm
- * @mmu_notifier: mmu notifier to track updates to CPU page table
- * @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
- */
-struct hmm {
-       struct mmu_notifier     mmu_notifier;
-       spinlock_t              ranges_lock;
-       struct list_head        ranges;
-       struct list_head        mirrors;
-       struct rw_semaphore     mirrors_sem;
-       wait_queue_head_t       wq;
-       long                    notifiers;
-};
-
 /*
  * hmm_pfn_flag_e - HMM flag enums
  *
@@ -143,9 +120,8 @@ enum hmm_pfn_value_e {
 /*
  * struct hmm_range - track invalidation lock on virtual address range
  *
- * @notifier: an optional mmu_interval_notifier
- * @notifier_seq: when notifier is used this is the result of
- *                mmu_interval_read_begin()
+ * @notifier: a mmu_interval_notifier that includes the start/end
+ * @notifier_seq: result of mmu_interval_read_begin()
  * @hmm: the core HMM structure this range is active against
  * @vma: the vm area struct for the range
  * @list: all range lock are on a list
@@ -162,8 +138,6 @@ enum hmm_pfn_value_e {
 struct hmm_range {
        struct mmu_interval_notifier *notifier;
        unsigned long           notifier_seq;
-       struct hmm              *hmm;
-       struct list_head        list;
        unsigned long           start;
        unsigned long           end;
        uint64_t                *pfns;
@@ -172,32 +146,8 @@ struct hmm_range {
        uint64_t                default_flags;
        uint64_t                pfn_flags_mask;
        uint8_t                 pfn_shift;
-       bool                    valid;
 };
 
-/*
- * hmm_range_wait_until_valid() - wait for range to be valid
- * @range: range affected by invalidation to wait on
- * @timeout: time out for wait in ms (ie abort wait after that period of time)
- * Return: true if the range is valid, false otherwise.
- */
-static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
-                                             unsigned long timeout)
-{
-       return wait_event_timeout(range->hmm->wq, range->valid,
-                                 msecs_to_jiffies(timeout)) != 0;
-}
-
-/*
- * hmm_range_valid() - test if a range is valid or not
- * @range: range
- * Return: true if the range is valid, false otherwise.
- */
-static inline bool hmm_range_valid(struct hmm_range *range)
-{
-       return range->valid;
-}
-
 /*
  * hmm_device_entry_to_page() - return struct page pointed to by a device entry
  * @range: range use to decode device entry value
@@ -267,111 +217,6 @@ static inline uint64_t hmm_device_entry_from_pfn(const 
struct hmm_range *range,
                range->flags[HMM_PFN_VALID];
 }
 
-/*
- * Mirroring: how to synchronize device page table with CPU page table.
- *
- * A device driver that is participating in HMM mirroring must always
- * synchronize with CPU page table updates. For this, device drivers can either
- * directly use mmu_notifier APIs or they can use the hmm_mirror API. Device
- * drivers can decide to register one mirror per device per process, or just
- * one mirror per process for a group of devices. The pattern is:
- *
- *      int device_bind_address_space(..., struct mm_struct *mm, ...)
- *      {
- *          struct device_address_space *das;
- *
- *          // Device driver specific initialization, and allocation of das
- *          // which contains an hmm_mirror struct as one of its fields.
- *          ...
- *
- *          ret = hmm_mirror_register(&das->mirror, mm, &device_mirror_ops);
- *          if (ret) {
- *              // Cleanup on error
- *              return ret;
- *          }
- *
- *          // Other device driver specific initialization
- *          ...
- *      }
- *
- * Once an hmm_mirror is registered for an address space, the device driver
- * will get callbacks through sync_cpu_device_pagetables() operation (see
- * hmm_mirror_ops struct).
- *
- * Device driver must not free the struct containing the hmm_mirror struct
- * before calling hmm_mirror_unregister(). The expected usage is to do that 
when
- * the device driver is unbinding from an address space.
- *
- *
- *      void device_unbind_address_space(struct device_address_space *das)
- *      {
- *          // Device driver specific cleanup
- *          ...
- *
- *          hmm_mirror_unregister(&das->mirror);
- *
- *          // Other device driver specific cleanup, and now das can be freed
- *          ...
- *      }
- */
-
-struct hmm_mirror;
-
-/*
- * struct hmm_mirror_ops - HMM mirror device operations callback
- *
- * @update: callback to update range on a device
- */
-struct hmm_mirror_ops {
-       /* release() - release hmm_mirror
-        *
-        * @mirror: pointer to struct hmm_mirror
-        *
-        * This is called when the mm_struct is being released.  The callback
-        * must ensure that all access to any pages obtained from this mirror
-        * is halted before the callback returns. All future access should
-        * fault.
-        */
-       void (*release)(struct hmm_mirror *mirror);
-
-       /* sync_cpu_device_pagetables() - synchronize page tables
-        *
-        * @mirror: pointer to struct hmm_mirror
-        * @update: update information (see struct mmu_notifier_range)
-        * Return: -EAGAIN if mmu_notifier_range_blockable(update) is false
-        * and callback needs to block, 0 otherwise.
-        *
-        * This callback ultimately originates from mmu_notifiers when the CPU
-        * page table is updated. The device driver must update its page table
-        * in response to this callback. The update argument tells what action
-        * to perform.
-        *
-        * The device driver must not return from this callback until the device
-        * page tables are completely updated (TLBs flushed, etc); this is a
-        * synchronous call.
-        */
-       int (*sync_cpu_device_pagetables)(
-               struct hmm_mirror *mirror,
-               const struct mmu_notifier_range *update);
-};
-
-/*
- * struct hmm_mirror - mirror struct for a device driver
- *
- * @hmm: pointer to struct hmm (which is unique per mm_struct)
- * @ops: device driver callback for HMM mirror operations
- * @list: for list of mirrors of a given mm
- *
- * Each address space (mm_struct) being mirrored by a device must register one
- * instance of an hmm_mirror struct with HMM. HMM will track the list of all
- * mirrors for each mm_struct.
- */
-struct hmm_mirror {
-       struct hmm                      *hmm;
-       const struct hmm_mirror_ops     *ops;
-       struct list_head                list;
-};
-
 /*
  * Retry fault if non-blocking, drop mmap_sem and return -EAGAIN in that case.
  */
@@ -381,15 +226,9 @@ struct hmm_mirror {
 #define HMM_FAULT_SNAPSHOT             (1 << 1)
 
 #ifdef CONFIG_HMM_MIRROR
-int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm);
-void hmm_mirror_unregister(struct hmm_mirror *mirror);
-
 /*
  * Please see Documentation/vm/hmm.rst for how to use the range API.
  */
-int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror);
-void hmm_range_unregister(struct hmm_range *range);
-
 long hmm_range_fault(struct hmm_range *range, unsigned int flags);
 
 long hmm_range_dma_map(struct hmm_range *range,
@@ -401,24 +240,6 @@ long hmm_range_dma_unmap(struct hmm_range *range,
                         dma_addr_t *daddrs,
                         bool dirty);
 #else
-int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
-{
-       return -EOPNOTSUPP;
-}
-
-void hmm_mirror_unregister(struct hmm_mirror *mirror)
-{
-}
-
-int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror)
-{
-       return -EOPNOTSUPP;
-}
-
-void hmm_range_unregister(struct hmm_range *range)
-{
-}
-
 static inline long hmm_range_fault(struct hmm_range *range, unsigned int flags)
 {
        return -EOPNOTSUPP;
diff --git a/mm/Kconfig b/mm/Kconfig
index d0b5046d9aeffd..e38ff1d5968dbf 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -675,7 +675,6 @@ config DEV_PAGEMAP_OPS
 config HMM_MIRROR
        bool
        depends on MMU
-       depends on MMU_NOTIFIER
 
 config DEVICE_PRIVATE
        bool "Unaddressable device memory (GPU memory, ...)"
diff --git a/mm/hmm.c b/mm/hmm.c
index 8d060c5dabe37b..aed2f39d1a986c 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -26,193 +26,6 @@
 #include <linux/mmu_notifier.h>
 #include <linux/memory_hotplug.h>
 
-static struct mmu_notifier *hmm_alloc_notifier(struct mm_struct *mm)
-{
-       struct hmm *hmm;
-
-       hmm = kzalloc(sizeof(*hmm), GFP_KERNEL);
-       if (!hmm)
-               return ERR_PTR(-ENOMEM);
-
-       init_waitqueue_head(&hmm->wq);
-       INIT_LIST_HEAD(&hmm->mirrors);
-       init_rwsem(&hmm->mirrors_sem);
-       INIT_LIST_HEAD(&hmm->ranges);
-       spin_lock_init(&hmm->ranges_lock);
-       hmm->notifiers = 0;
-       return &hmm->mmu_notifier;
-}
-
-static void hmm_free_notifier(struct mmu_notifier *mn)
-{
-       struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
-
-       WARN_ON(!list_empty(&hmm->ranges));
-       WARN_ON(!list_empty(&hmm->mirrors));
-       kfree(hmm);
-}
-
-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;
-
-       /*
-        * 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_read(&hmm->mirrors_sem);
-       list_for_each_entry(mirror, &hmm->mirrors, list) {
-               /*
-                * Note: The driver is not allowed to trigger
-                * hmm_mirror_unregister() from this thread.
-                */
-               if (mirror->ops->release)
-                       mirror->ops->release(mirror);
-       }
-       up_read(&hmm->mirrors_sem);
-}
-
-static void notifiers_decrement(struct hmm *hmm)
-{
-       unsigned long flags;
-
-       spin_lock_irqsave(&hmm->ranges_lock, flags);
-       hmm->notifiers--;
-       if (!hmm->notifiers) {
-               struct hmm_range *range;
-
-               list_for_each_entry(range, &hmm->ranges, list) {
-                       if (range->valid)
-                               continue;
-                       range->valid = true;
-               }
-               wake_up_all(&hmm->wq);
-       }
-       spin_unlock_irqrestore(&hmm->ranges_lock, flags);
-}
-
-static int hmm_invalidate_range_start(struct mmu_notifier *mn,
-                       const struct mmu_notifier_range *nrange)
-{
-       struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
-       struct hmm_mirror *mirror;
-       struct hmm_range *range;
-       unsigned long flags;
-       int ret = 0;
-
-       spin_lock_irqsave(&hmm->ranges_lock, flags);
-       hmm->notifiers++;
-       list_for_each_entry(range, &hmm->ranges, list) {
-               if (nrange->end < range->start || nrange->start >= range->end)
-                       continue;
-
-               range->valid = false;
-       }
-       spin_unlock_irqrestore(&hmm->ranges_lock, flags);
-
-       if (mmu_notifier_range_blockable(nrange))
-               down_read(&hmm->mirrors_sem);
-       else if (!down_read_trylock(&hmm->mirrors_sem)) {
-               ret = -EAGAIN;
-               goto out;
-       }
-
-       list_for_each_entry(mirror, &hmm->mirrors, list) {
-               int rc;
-
-               rc = mirror->ops->sync_cpu_device_pagetables(mirror, nrange);
-               if (rc) {
-                       if (WARN_ON(mmu_notifier_range_blockable(nrange) ||
-                           rc != -EAGAIN))
-                               continue;
-                       ret = -EAGAIN;
-                       break;
-               }
-       }
-       up_read(&hmm->mirrors_sem);
-
-out:
-       if (ret)
-               notifiers_decrement(hmm);
-       return ret;
-}
-
-static void hmm_invalidate_range_end(struct mmu_notifier *mn,
-                       const struct mmu_notifier_range *nrange)
-{
-       struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier);
-
-       notifiers_decrement(hmm);
-}
-
-static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
-       .release                = hmm_release,
-       .invalidate_range_start = hmm_invalidate_range_start,
-       .invalidate_range_end   = hmm_invalidate_range_end,
-       .alloc_notifier         = hmm_alloc_notifier,
-       .free_notifier          = hmm_free_notifier,
-};
-
-/*
- * hmm_mirror_register() - register a mirror against an mm
- *
- * @mirror: new mirror struct to register
- * @mm: mm to register against
- * Return: 0 on success, -ENOMEM if no memory, -EINVAL if invalid arguments
- *
- * To start mirroring a process address space, the device driver must register
- * an HMM mirror struct.
- *
- * The caller cannot unregister the hmm_mirror while any ranges are
- * registered.
- *
- * Callers using this function must put a call to mmu_notifier_synchronize()
- * in their module exit functions.
- */
-int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
-{
-       struct mmu_notifier *mn;
-
-       lockdep_assert_held_write(&mm->mmap_sem);
-
-       /* Sanity check */
-       if (!mm || !mirror || !mirror->ops)
-               return -EINVAL;
-
-       mn = mmu_notifier_get_locked(&hmm_mmu_notifier_ops, mm);
-       if (IS_ERR(mn))
-               return PTR_ERR(mn);
-       mirror->hmm = container_of(mn, struct hmm, mmu_notifier);
-
-       down_write(&mirror->hmm->mirrors_sem);
-       list_add(&mirror->list, &mirror->hmm->mirrors);
-       up_write(&mirror->hmm->mirrors_sem);
-
-       return 0;
-}
-EXPORT_SYMBOL(hmm_mirror_register);
-
-/*
- * hmm_mirror_unregister() - unregister a mirror
- *
- * @mirror: mirror struct to unregister
- *
- * Stop mirroring a process address space, and cleanup.
- */
-void hmm_mirror_unregister(struct hmm_mirror *mirror)
-{
-       struct hmm *hmm = mirror->hmm;
-
-       down_write(&hmm->mirrors_sem);
-       list_del(&mirror->list);
-       up_write(&hmm->mirrors_sem);
-       mmu_notifier_put(&hmm->mmu_notifier);
-}
-EXPORT_SYMBOL(hmm_mirror_unregister);
-
 struct hmm_vma_walk {
        struct hmm_range        *range;
        struct dev_pagemap      *pgmap;
@@ -785,87 +598,6 @@ static void hmm_pfns_clear(struct hmm_range *range,
                *pfns = range->values[HMM_PFN_NONE];
 }
 
-/*
- * hmm_range_register() - start tracking change to CPU page table over a range
- * @range: range
- * @mm: the mm struct for the range of virtual address
- *
- * Return: 0 on success, -EFAULT if the address space is no longer valid
- *
- * Track updates to the CPU page table see include/linux/hmm.h
- */
-int hmm_range_register(struct hmm_range *range, struct hmm_mirror *mirror)
-{
-       struct hmm *hmm = mirror->hmm;
-       unsigned long flags;
-
-       range->valid = false;
-       range->hmm = NULL;
-
-       if ((range->start & (PAGE_SIZE - 1)) || (range->end & (PAGE_SIZE - 1)))
-               return -EINVAL;
-       if (range->start >= range->end)
-               return -EINVAL;
-
-       /* Prevent hmm_release() from running while the range is valid */
-       if (!mmget_not_zero(hmm->mmu_notifier.mm))
-               return -EFAULT;
-
-       /* Initialize range to track CPU page table updates. */
-       spin_lock_irqsave(&hmm->ranges_lock, flags);
-
-       range->hmm = hmm;
-       list_add(&range->list, &hmm->ranges);
-
-       /*
-        * If there are any concurrent notifiers we have to wait for them for
-        * the range to be valid (see hmm_range_wait_until_valid()).
-        */
-       if (!hmm->notifiers)
-               range->valid = true;
-       spin_unlock_irqrestore(&hmm->ranges_lock, flags);
-
-       return 0;
-}
-EXPORT_SYMBOL(hmm_range_register);
-
-/*
- * hmm_range_unregister() - stop tracking change to CPU page table over a range
- * @range: range
- *
- * Range struct is used to track updates to the CPU page table after a call to
- * hmm_range_register(). See include/linux/hmm.h for how to use it.
- */
-void hmm_range_unregister(struct hmm_range *range)
-{
-       struct hmm *hmm = range->hmm;
-       unsigned long flags;
-
-       spin_lock_irqsave(&hmm->ranges_lock, flags);
-       list_del_init(&range->list);
-       spin_unlock_irqrestore(&hmm->ranges_lock, flags);
-
-       /* Drop reference taken by hmm_range_register() */
-       mmput(hmm->mmu_notifier.mm);
-
-       /*
-        * The range is now invalid and the ref on the hmm is dropped, so
-        * poison the pointer.  Leave other fields in place, for the caller's
-        * use.
-        */
-       range->valid = false;
-       memset(&range->hmm, POISON_INUSE, sizeof(range->hmm));
-}
-EXPORT_SYMBOL(hmm_range_unregister);
-
-static bool needs_retry(struct hmm_range *range)
-{
-       if (range->notifier)
-               return mmu_interval_check_retry(range->notifier,
-                                               range->notifier_seq);
-       return !range->valid;
-}
-
 static const struct mm_walk_ops hmm_walk_ops = {
        .pud_entry      = hmm_vma_walk_pud,
        .pmd_entry      = hmm_vma_walk_pmd,
@@ -906,20 +638,16 @@ long hmm_range_fault(struct hmm_range *range, unsigned 
int flags)
        const unsigned long device_vma = VM_IO | VM_PFNMAP | VM_MIXEDMAP;
        unsigned long start = range->start, end;
        struct hmm_vma_walk hmm_vma_walk;
-       struct mm_struct *mm;
+       struct mm_struct *mm = range->notifier->mm;
        struct vm_area_struct *vma;
        int ret;
 
-       if (range->notifier)
-               mm = range->notifier->mm;
-       else
-               mm = range->hmm->mmu_notifier.mm;
-
        lockdep_assert_held(&mm->mmap_sem);
 
        do {
                /* If range is no longer valid force retry. */
-               if (needs_retry(range))
+               if (mmu_interval_check_retry(range->notifier,
+                                            range->notifier_seq))
                        return -EBUSY;
 
                vma = find_vma(mm, start);
@@ -952,7 +680,9 @@ long hmm_range_fault(struct hmm_range *range, unsigned int 
flags)
                        start = hmm_vma_walk.last;
 
                        /* Keep trying while the range is valid. */
-               } while (ret == -EBUSY && !needs_retry(range));
+               } while (ret == -EBUSY &&
+                        !mmu_interval_check_retry(range->notifier,
+                                                  range->notifier_seq));
 
                if (ret) {
                        unsigned long i;
@@ -1010,7 +740,8 @@ long hmm_range_dma_map(struct hmm_range *range, struct 
device *device,
                        continue;
 
                /* Check if range is being invalidated */
-               if (needs_retry(range)) {
+               if (mmu_interval_check_retry(range->notifier,
+                                            range->notifier_seq)) {
                        ret = -EBUSY;
                        goto unmap;
                }
-- 
2.24.0


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