[PATCH v2 hmm 2/9] mm/hmm: return the fault type from hmm_pte_need_fault()
Jason Gunthorpe
jgg at ziepe.ca
Fri Mar 27 20:00:14 UTC 2020
From: Jason Gunthorpe <jgg at mellanox.com>
Using two bools instead of flags return is not necessary and leads to
bugs. Returning a value is easier for the compiler to check and easier to
pass around the code flow.
Convert the two bools into flags and push the change to all callers.
Signed-off-by: Jason Gunthorpe <jgg at mellanox.com>
---
mm/hmm.c | 183 ++++++++++++++++++++++++-------------------------------
1 file changed, 81 insertions(+), 102 deletions(-)
diff --git a/mm/hmm.c b/mm/hmm.c
index 3a2610e0713329..d208ddd351066f 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -32,6 +32,12 @@ struct hmm_vma_walk {
unsigned int flags;
};
+enum {
+ HMM_NEED_FAULT = 1 << 0,
+ HMM_NEED_WRITE_FAULT = 1 << 1,
+ HMM_NEED_ALL_BITS = HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT,
+};
+
static int hmm_pfns_fill(unsigned long addr, unsigned long end,
struct hmm_range *range, enum hmm_pfn_value_e value)
{
@@ -49,8 +55,7 @@ static int hmm_pfns_fill(unsigned long addr, unsigned long end,
* hmm_vma_fault() - fault in a range lacking valid pmd or pte(s)
* @addr: range virtual start address (inclusive)
* @end: range virtual end address (exclusive)
- * @fault: should we fault or not ?
- * @write_fault: write fault ?
+ * @required_fault: HMM_NEED_* flags
* @walk: mm_walk structure
* Return: -EBUSY after page fault, or page fault error
*
@@ -58,8 +63,7 @@ static int hmm_pfns_fill(unsigned long addr, unsigned long end,
* or whenever there is no page directory covering the virtual address range.
*/
static int hmm_vma_fault(unsigned long addr, unsigned long end,
- bool fault, bool write_fault,
- struct mm_walk *walk)
+ unsigned int required_fault, struct mm_walk *walk)
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
@@ -68,13 +72,13 @@ static int hmm_vma_fault(unsigned long addr, unsigned long end,
unsigned long i = (addr - range->start) >> PAGE_SHIFT;
unsigned int fault_flags = FAULT_FLAG_REMOTE;
- WARN_ON_ONCE(!fault && !write_fault);
+ WARN_ON_ONCE(!required_fault);
hmm_vma_walk->last = addr;
if (!vma)
goto out_error;
- if (write_fault) {
+ if (required_fault & HMM_NEED_WRITE_FAULT) {
if (!(vma->vm_flags & VM_WRITE))
return -EPERM;
fault_flags |= FAULT_FLAG_WRITE;
@@ -91,14 +95,13 @@ static int hmm_vma_fault(unsigned long addr, unsigned long end,
return -EFAULT;
}
-static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
- uint64_t pfns, uint64_t cpu_flags,
- bool *fault, bool *write_fault)
+static unsigned int hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
+ uint64_t pfns, uint64_t cpu_flags)
{
struct hmm_range *range = hmm_vma_walk->range;
if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT)
- return;
+ return 0;
/*
* So we not only consider the individual per page request we also
@@ -114,37 +117,37 @@ static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
/* We aren't ask to do anything ... */
if (!(pfns & range->flags[HMM_PFN_VALID]))
- return;
+ return 0;
- /* If CPU page table is not valid then we need to fault */
- *fault = !(cpu_flags & range->flags[HMM_PFN_VALID]);
/* Need to write fault ? */
if ((pfns & range->flags[HMM_PFN_WRITE]) &&
- !(cpu_flags & range->flags[HMM_PFN_WRITE])) {
- *write_fault = true;
- *fault = true;
- }
+ !(cpu_flags & range->flags[HMM_PFN_WRITE]))
+ return HMM_NEED_FAULT | HMM_NEED_WRITE_FAULT;
+
+ /* If CPU page table is not valid then we need to fault */
+ if (!(cpu_flags & range->flags[HMM_PFN_VALID]))
+ return HMM_NEED_FAULT;
+ return 0;
}
-static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
- const uint64_t *pfns, unsigned long npages,
- uint64_t cpu_flags, bool *fault,
- bool *write_fault)
+static unsigned int
+hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
+ const uint64_t *pfns, unsigned long npages,
+ uint64_t cpu_flags)
{
+ unsigned int required_fault = 0;
unsigned long i;
- if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT) {
- *fault = *write_fault = false;
- return;
- }
+ if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT)
+ return 0;
- *fault = *write_fault = false;
for (i = 0; i < npages; ++i) {
- hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags,
- fault, write_fault);
- if ((*write_fault))
- return;
+ required_fault |=
+ hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags);
+ if (required_fault == HMM_NEED_ALL_BITS)
+ return required_fault;
}
+ return required_fault;
}
static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
@@ -152,17 +155,16 @@ static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
- bool fault, write_fault;
+ unsigned int required_fault;
unsigned long i, npages;
uint64_t *pfns;
i = (addr - range->start) >> PAGE_SHIFT;
npages = (end - addr) >> PAGE_SHIFT;
pfns = &range->pfns[i];
- hmm_range_need_fault(hmm_vma_walk, pfns, npages,
- 0, &fault, &write_fault);
- if (fault || write_fault)
- return hmm_vma_fault(addr, end, fault, write_fault, walk);
+ required_fault = hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0);
+ if (required_fault)
+ return hmm_vma_fault(addr, end, required_fault, walk);
hmm_vma_walk->last = addr;
return hmm_pfns_fill(addr, end, range, HMM_PFN_NONE);
}
@@ -183,16 +185,15 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
unsigned long pfn, npages, i;
- bool fault, write_fault;
+ unsigned int required_fault;
uint64_t cpu_flags;
npages = (end - addr) >> PAGE_SHIFT;
cpu_flags = pmd_to_hmm_pfn_flags(range, pmd);
- hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
- &fault, &write_fault);
-
- if (fault || write_fault)
- return hmm_vma_fault(addr, end, fault, write_fault, walk);
+ required_fault =
+ hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags);
+ if (required_fault)
+ return hmm_vma_fault(addr, end, required_fault, walk);
pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
@@ -229,18 +230,15 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
- bool fault, write_fault;
+ unsigned int required_fault;
uint64_t cpu_flags;
pte_t pte = *ptep;
uint64_t orig_pfn = *pfn;
*pfn = range->values[HMM_PFN_NONE];
- fault = write_fault = false;
-
if (pte_none(pte)) {
- hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0,
- &fault, &write_fault);
- if (fault || write_fault)
+ required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0);
+ if (required_fault)
goto fault;
return 0;
}
@@ -261,9 +259,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
return 0;
}
- hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0, &fault,
- &write_fault);
- if (!fault && !write_fault)
+ required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0);
+ if (!required_fault)
return 0;
if (!non_swap_entry(entry))
@@ -283,9 +280,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
}
cpu_flags = pte_to_hmm_pfn_flags(range, pte);
- hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags, &fault,
- &write_fault);
- if (fault || write_fault)
+ required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags);
+ if (required_fault)
goto fault;
/*
@@ -293,9 +289,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
* fall through and treat it like a normal page.
*/
if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {
- hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0, &fault,
- &write_fault);
- if (fault || write_fault) {
+ if (hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0)) {
pte_unmap(ptep);
return -EFAULT;
}
@@ -309,7 +303,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
fault:
pte_unmap(ptep);
/* Fault any virtual address we were asked to fault */
- return hmm_vma_fault(addr, end, fault, write_fault, walk);
+ return hmm_vma_fault(addr, end, required_fault, walk);
}
static int hmm_vma_walk_pmd(pmd_t *pmdp,
@@ -322,7 +316,6 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
uint64_t *pfns = &range->pfns[(start - range->start) >> PAGE_SHIFT];
unsigned long npages = (end - start) >> PAGE_SHIFT;
unsigned long addr = start;
- bool fault, write_fault;
pte_t *ptep;
pmd_t pmd;
@@ -332,9 +325,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
return hmm_vma_walk_hole(start, end, -1, walk);
if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
- hmm_range_need_fault(hmm_vma_walk, pfns, npages,
- 0, &fault, &write_fault);
- if (fault || write_fault) {
+ if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0)) {
hmm_vma_walk->last = addr;
pmd_migration_entry_wait(walk->mm, pmdp);
return -EBUSY;
@@ -343,9 +334,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
}
if (!pmd_present(pmd)) {
- hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0, &fault,
- &write_fault);
- if (fault || write_fault)
+ if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0))
return -EFAULT;
return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
}
@@ -375,9 +364,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
* recover.
*/
if (pmd_bad(pmd)) {
- hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0, &fault,
- &write_fault);
- if (fault || write_fault)
+ if (hmm_range_need_fault(hmm_vma_walk, pfns, npages, 0))
return -EFAULT;
return hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
}
@@ -434,8 +421,8 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
if (pud_huge(pud) && pud_devmap(pud)) {
unsigned long i, npages, pfn;
+ unsigned int required_fault;
uint64_t *pfns, cpu_flags;
- bool fault, write_fault;
if (!pud_present(pud)) {
spin_unlock(ptl);
@@ -447,12 +434,11 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
pfns = &range->pfns[i];
cpu_flags = pud_to_hmm_pfn_flags(range, pud);
- hmm_range_need_fault(hmm_vma_walk, pfns, npages,
- cpu_flags, &fault, &write_fault);
- if (fault || write_fault) {
+ required_fault = hmm_range_need_fault(hmm_vma_walk, pfns,
+ npages, cpu_flags);
+ if (required_fault) {
spin_unlock(ptl);
- return hmm_vma_fault(addr, end, fault, write_fault,
- walk);
+ return hmm_vma_fault(addr, end, required_fault, walk);
}
pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
@@ -484,7 +470,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
struct hmm_range *range = hmm_vma_walk->range;
struct vm_area_struct *vma = walk->vma;
uint64_t orig_pfn, cpu_flags;
- bool fault, write_fault;
+ unsigned int required_fault;
spinlock_t *ptl;
pte_t entry;
@@ -495,12 +481,10 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
orig_pfn = range->pfns[i];
range->pfns[i] = range->values[HMM_PFN_NONE];
cpu_flags = pte_to_hmm_pfn_flags(range, entry);
- fault = write_fault = false;
- hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
- &fault, &write_fault);
- if (fault || write_fault) {
+ required_fault = hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags);
+ if (required_fault) {
spin_unlock(ptl);
- return hmm_vma_fault(addr, end, fault, write_fault, walk);
+ return hmm_vma_fault(addr, end, required_fault, walk);
}
pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);
@@ -522,37 +506,32 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
struct hmm_range *range = hmm_vma_walk->range;
struct vm_area_struct *vma = walk->vma;
+ if (!(vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) &&
+ vma->vm_flags & VM_READ)
+ return 0;
+
/*
- * Skip vma ranges that don't have struct page backing them or map I/O
- * devices directly.
+ * vma ranges that don't have struct page backing them or map I/O
+ * devices directly cannot be handled by hmm_range_fault().
*
* If the vma does not allow read access, then assume that it does not
* allow write access either. HMM does not support architectures that
* allow write without read.
+ *
+ * If a fault is requested for an unsupported range then it is a hard
+ * failure.
*/
- if ((vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) ||
- !(vma->vm_flags & VM_READ)) {
- bool fault, write_fault;
-
- /*
- * Check to see if a fault is requested for any page in the
- * range.
- */
- hmm_range_need_fault(hmm_vma_walk, range->pfns +
- ((start - range->start) >> PAGE_SHIFT),
- (end - start) >> PAGE_SHIFT,
- 0, &fault, &write_fault);
- if (fault || write_fault)
- return -EFAULT;
-
- hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
- hmm_vma_walk->last = end;
+ if (hmm_range_need_fault(hmm_vma_walk,
+ range->pfns +
+ ((start - range->start) >> PAGE_SHIFT),
+ (end - start) >> PAGE_SHIFT, 0))
+ return -EFAULT;
- /* Skip this vma and continue processing the next vma. */
- return 1;
- }
+ hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
+ hmm_vma_walk->last = end;
- return 0;
+ /* Skip this vma and continue processing the next vma. */
+ return 1;
}
static const struct mm_walk_ops hmm_walk_ops = {
--
2.25.2
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