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mm/hmm: return the fault type from hmm_pte_need_fault() 

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.

Link: https://lore.kernel.org/r/20200327200021.29372-3-jgg@ziepe.ca
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2020-03-27 17:00:14 -03:00
parent 068354ade5
commit a3eb13c157
1 changed files with 81 additions and 102 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

169
mm/hmm.c
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@ -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,
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, bool *fault,
bool *write_fault)
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);
@ -522,27 +506,25 @@ 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 +
if (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)
(end - start) >> PAGE_SHIFT, 0))
return -EFAULT;
hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
@ -552,9 +534,6 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
return 1;
}
return 0;
}
static const struct mm_walk_ops hmm_walk_ops = {
.pud_entry = hmm_vma_walk_pud,
.pmd_entry = hmm_vma_walk_pmd,