[PATCH v2 4/7] mm: merge hmm_range_snapshot into hmm_range_fault
Ralph Campbell
rcampbell at nvidia.com
Fri Jul 26 00:56:47 UTC 2019
From: Christoph Hellwig <hch at lst.de>
Add a HMM_FAULT_SNAPSHOT flag so that hmm_range_snapshot can be merged
into the almost identical hmm_range_fault function.
Signed-off-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Ralph Campbell <rcampbell at nvidia.com>
Cc: "Jérôme Glisse" <jglisse at redhat.com>
Cc: Jason Gunthorpe <jgg at mellanox.com>
---
Documentation/vm/hmm.rst | 17 ++++----
include/linux/hmm.h | 4 +-
mm/hmm.c | 85 +---------------------------------------
3 files changed, 13 insertions(+), 93 deletions(-)
diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
index 710ce1c701bf..ddcb5ca8b296 100644
--- a/Documentation/vm/hmm.rst
+++ b/Documentation/vm/hmm.rst
@@ -192,15 +192,14 @@ 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 either::
+use::
- long hmm_range_snapshot(struct hmm_range *range);
- long hmm_range_fault(struct hmm_range *range, bool block);
+ long hmm_range_fault(struct hmm_range *range, unsigned int flags);
-The first one (hmm_range_snapshot()) will only fetch present CPU page table
+With the HMM_RANGE_SNAPSHOT flag, it will only fetch present CPU page table
entries and will not trigger a page fault on missing or non-present entries.
-The second one does trigger a page fault on missing or read-only entries if
-write access is requested (see below). Page faults use the generic mm page
+Without that flag, it does trigger a page fault on missing or read-only entries
+if write access is requested (see below). Page faults use the generic mm page
fault code path just like a CPU page fault.
Both functions copy CPU page table entries into their pfns array argument. Each
@@ -227,20 +226,20 @@ The usage pattern is::
/*
* Just wait for range to be valid, safe to ignore return value as we
- * will use the return value of hmm_range_snapshot() below under the
+ * 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);
again:
down_read(&mm->mmap_sem);
- ret = hmm_range_snapshot(&range);
+ 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_snapshot()
+ * on retry we will get proper error with hmm_range_fault()
*/
hmm_range_wait_until_valid(&range, TIMEOUT_IN_MSEC);
goto again;
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 15f1b113be3c..f3693dcc8b98 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -412,7 +412,9 @@ void hmm_range_unregister(struct hmm_range *range);
*/
#define HMM_FAULT_ALLOW_RETRY (1 << 0)
-long hmm_range_snapshot(struct hmm_range *range);
+/* Don't fault in missing PTEs, just snapshot the current state. */
+#define HMM_FAULT_SNAPSHOT (1 << 1)
+
long hmm_range_fault(struct hmm_range *range, unsigned int flags);
long hmm_range_dma_map(struct hmm_range *range,
diff --git a/mm/hmm.c b/mm/hmm.c
index 84f2791d3510..1bc014cddd78 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -280,7 +280,6 @@ struct hmm_vma_walk {
struct hmm_range *range;
struct dev_pagemap *pgmap;
unsigned long last;
- bool fault;
unsigned int flags;
};
@@ -373,7 +372,7 @@ static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
{
struct hmm_range *range = hmm_vma_walk->range;
- if (!hmm_vma_walk->fault)
+ if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT)
return;
/*
@@ -418,7 +417,7 @@ static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
{
unsigned long i;
- if (!hmm_vma_walk->fault) {
+ if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) {
*fault = *write_fault = false;
return;
}
@@ -936,85 +935,6 @@ void hmm_range_unregister(struct hmm_range *range)
}
EXPORT_SYMBOL(hmm_range_unregister);
-/*
- * hmm_range_snapshot() - snapshot CPU page table for a range
- * @range: range
- * Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
- * permission (for instance asking for write and range is read only),
- * -EBUSY if you need to retry, -EFAULT invalid (ie either no valid
- * vma or it is illegal to access that range), number of valid pages
- * in range->pfns[] (from range start address).
- *
- * This snapshots the CPU page table for a range of virtual addresses. Snapshot
- * validity is tracked by range struct. See in include/linux/hmm.h for example
- * on how to use.
- */
-long hmm_range_snapshot(struct hmm_range *range)
-{
- 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 hmm *hmm = range->hmm;
- struct vm_area_struct *vma;
- struct mm_walk mm_walk;
-
- lockdep_assert_held(&hmm->mm->mmap_sem);
- do {
- /* If range is no longer valid force retry. */
- if (!range->valid)
- return -EBUSY;
-
- vma = find_vma(hmm->mm, start);
- if (vma == NULL || (vma->vm_flags & device_vma))
- return -EFAULT;
-
- if (is_vm_hugetlb_page(vma)) {
- if (huge_page_shift(hstate_vma(vma)) !=
- range->page_shift &&
- range->page_shift != PAGE_SHIFT)
- return -EINVAL;
- } else {
- if (range->page_shift != PAGE_SHIFT)
- return -EINVAL;
- }
-
- if (!(vma->vm_flags & VM_READ)) {
- /*
- * If vma do not allow read access, then assume that it
- * does not allow write access, either. HMM does not
- * support architecture that allow write without read.
- */
- hmm_pfns_clear(range, range->pfns,
- range->start, range->end);
- return -EPERM;
- }
-
- range->vma = vma;
- hmm_vma_walk.pgmap = NULL;
- hmm_vma_walk.last = start;
- hmm_vma_walk.fault = false;
- hmm_vma_walk.range = range;
- mm_walk.private = &hmm_vma_walk;
- end = min(range->end, vma->vm_end);
-
- mm_walk.vma = vma;
- mm_walk.mm = vma->vm_mm;
- mm_walk.pte_entry = NULL;
- mm_walk.test_walk = NULL;
- mm_walk.hugetlb_entry = NULL;
- mm_walk.pud_entry = hmm_vma_walk_pud;
- mm_walk.pmd_entry = hmm_vma_walk_pmd;
- mm_walk.pte_hole = hmm_vma_walk_hole;
- mm_walk.hugetlb_entry = hmm_vma_walk_hugetlb_entry;
-
- walk_page_range(start, end, &mm_walk);
- start = end;
- } while (start < range->end);
-
- return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
-}
-EXPORT_SYMBOL(hmm_range_snapshot);
-
/**
* hmm_range_fault - try to fault some address in a virtual address range
* @range: range being faulted
@@ -1088,7 +1008,6 @@ long hmm_range_fault(struct hmm_range *range, unsigned int flags)
range->vma = vma;
hmm_vma_walk.pgmap = NULL;
hmm_vma_walk.last = start;
- hmm_vma_walk.fault = true;
hmm_vma_walk.flags = flags;
hmm_vma_walk.range = range;
mm_walk.private = &hmm_vma_walk;
--
2.20.1
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