[PATCH v2 hmm 2/9] mm/hmm: return the fault type from hmm_pte_need_fault()

From: Jason Gunthorpe jgg@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@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 = {