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-rw-r--r--Documentation/vm/hmm.rst26
-rw-r--r--include/linux/hmm.h4
-rw-r--r--mm/hmm.c31
3 files changed, 37 insertions, 24 deletions
diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
index 44205f0b671f..d9b27bdadd1b 100644
--- a/Documentation/vm/hmm.rst
+++ b/Documentation/vm/hmm.rst
@@ -189,11 +189,7 @@ the driver callback returns.
When the device driver wants to populate a range of virtual addresses, it can
use either::
- int hmm_vma_get_pfns(struct vm_area_struct *vma,
- struct hmm_range *range,
- unsigned long start,
- unsigned long end,
- hmm_pfn_t *pfns);
+ long hmm_range_snapshot(struct hmm_range *range);
int hmm_vma_fault(struct vm_area_struct *vma,
struct hmm_range *range,
unsigned long start,
@@ -202,7 +198,7 @@ use either::
bool write,
bool block);
-The first one (hmm_vma_get_pfns()) will only fetch present CPU page table
+The first one (hmm_range_snapshot()) 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 entry if the
write parameter is true. Page faults use the generic mm page fault code path
@@ -220,19 +216,33 @@ respect in order to keep things properly synchronized. The usage pattern is::
{
struct hmm_range range;
...
+
+ range.start = ...;
+ range.end = ...;
+ range.pfns = ...;
+ range.flags = ...;
+ range.values = ...;
+ range.pfn_shift = ...;
+
again:
- ret = hmm_vma_get_pfns(vma, &range, start, end, pfns);
- if (ret)
+ down_read(&mm->mmap_sem);
+ range.vma = ...;
+ ret = hmm_range_snapshot(&range);
+ if (ret) {
+ up_read(&mm->mmap_sem);
return ret;
+ }
take_lock(driver->update);
if (!hmm_vma_range_done(vma, &range)) {
release_lock(driver->update);
+ up_read(&mm->mmap_sem);
goto again;
}
// Use pfns array content to update device page table
release_lock(driver->update);
+ up_read(&mm->mmap_sem);
return 0;
}
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 716fc61fa6d4..32206b0b1bfd 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -365,11 +365,11 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror);
* table invalidation serializes on it.
*
* YOU MUST CALL hmm_vma_range_done() ONCE AND ONLY ONCE EACH TIME YOU CALL
- * hmm_vma_get_pfns() WITHOUT ERROR !
+ * hmm_range_snapshot() WITHOUT ERROR !
*
* IF YOU DO NOT FOLLOW THE ABOVE RULE THE SNAPSHOT CONTENT MIGHT BE INVALID !
*/
-int hmm_vma_get_pfns(struct hmm_range *range);
+long hmm_range_snapshot(struct hmm_range *range);
bool hmm_vma_range_done(struct hmm_range *range);
diff --git a/mm/hmm.c b/mm/hmm.c
index 84e0577a912a..bd957a9f10d1 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -702,23 +702,25 @@ static void hmm_pfns_special(struct hmm_range *range)
}
/*
- * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
- * @range: range being snapshotted
- * Returns: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
- * vma permission, 0 success
+ * hmm_range_snapshot() - snapshot CPU page table for a range
+ * @range: range
+ * Returns: number of valid pages in range->pfns[] (from range start
+ * address). This may be zero. If the return value is negative,
+ * then one of the following values may be returned:
+ *
+ * -EINVAL invalid arguments or mm or virtual address are in an
+ * invalid vma (ie either hugetlbfs or device file vma).
+ * -EPERM For example, asking for write, when the range is
+ * read-only
+ * -EAGAIN Caller needs to retry
+ * -EFAULT Either no valid vma exists for this range, or it is
+ * illegal to access the range
*
* This snapshots the CPU page table for a range of virtual addresses. Snapshot
* validity is tracked by range struct. See hmm_vma_range_done() for further
* information.
- *
- * The range struct is initialized here. It tracks the CPU page table, but only
- * if the function returns success (0), in which case the caller must then call
- * hmm_vma_range_done() to stop CPU page table update tracking on this range.
- *
- * NOT CALLING hmm_vma_range_done() IF FUNCTION RETURNS 0 WILL LEAD TO SERIOUS
- * MEMORY CORRUPTION ! YOU HAVE BEEN WARNED !
*/
-int hmm_vma_get_pfns(struct hmm_range *range)
+long hmm_range_snapshot(struct hmm_range *range)
{
struct vm_area_struct *vma = range->vma;
struct hmm_vma_walk hmm_vma_walk;
@@ -772,6 +774,7 @@ int hmm_vma_get_pfns(struct hmm_range *range)
hmm_vma_walk.fault = false;
hmm_vma_walk.range = range;
mm_walk.private = &hmm_vma_walk;
+ hmm_vma_walk.last = range->start;
mm_walk.vma = vma;
mm_walk.mm = vma->vm_mm;
@@ -788,9 +791,9 @@ int hmm_vma_get_pfns(struct hmm_range *range)
* function return 0).
*/
range->hmm = hmm;
- return 0;
+ return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
}
-EXPORT_SYMBOL(hmm_vma_get_pfns);
+EXPORT_SYMBOL(hmm_range_snapshot);
/*
* hmm_vma_range_done() - stop tracking change to CPU page table over a range