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mm/hmm: don't handle the non-fault case in hmm_vma_walk_hole_() 

Setting a pfns entry to NONE before returning -EBUSY is a bug that will
cause corruption of the input flags on the next loop.

There is just a single caller using hmm_vma_walk_hole_() for the non-fault
case.  Use hmm_pfns_fill() to fill the whole pfn array with zeroes in the
only caller for the non-fault case and remove the non-fault path from
hmm_vma_walk_hole_(). This avoids setting NONE before returning -EBUSY.

Also rename the function to hmm_vma_fault() to better describe what it
does.

Fixes: 2aee09d8c1 ("mm/hmm: change hmm_vma_fault() to allow write fault on page basis")
Link: https://lore.kernel.org/r/20200316135310.899364-5-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Christoph Hellwig 2020-03-16 14:53:09 +01:00 committed by Jason Gunthorpe
parent 45050692de
commit f8c888a304
1 changed files with 18 additions and 19 deletions
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37
mm/hmm.c
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@ -73,45 +73,41 @@ static int hmm_pfns_fill(unsigned long addr, unsigned long end,
}
/*
* hmm_vma_walk_hole_() - handle a range lacking valid pmd or pte(s)
* 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 ?
* @walk: mm_walk structure
* Return: 0 on success, -EBUSY after page fault, or page fault error
* Return: -EBUSY after page fault, or page fault error
*
* This function will be called whenever pmd_none() or pte_none() returns true,
* or whenever there is no page directory covering the virtual address range.
*/
static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
static int hmm_vma_fault(unsigned long addr, unsigned long end,
bool fault, bool write_fault,
struct mm_walk *walk)
{
struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range;
uint64_t *pfns = range->pfns;
unsigned long i;
unsigned long i = (addr - range->start) >> PAGE_SHIFT;
WARN_ON_ONCE(!fault && !write_fault);
hmm_vma_walk->last = addr;
i = (addr - range->start) >> PAGE_SHIFT;
if (write_fault && walk->vma && !(walk->vma->vm_flags & VM_WRITE))
return -EPERM;
for (; addr < end; addr += PAGE_SIZE, i++) {
pfns[i] = range->values[HMM_PFN_NONE];
if (fault || write_fault) {
int ret;
int ret;
ret = hmm_vma_do_fault(walk, addr, write_fault,
&pfns[i]);
if (ret != -EBUSY)
return ret;
}
ret = hmm_vma_do_fault(walk, addr, write_fault, &pfns[i]);
if (ret != -EBUSY)
return ret;
}
return (fault || write_fault) ? -EBUSY : 0;
return -EBUSY;
}
static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
@ -193,7 +189,10 @@ static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
pfns = &range->pfns[i];
hmm_range_need_fault(hmm_vma_walk, pfns, npages,
0, &fault, &write_fault);
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
if (fault || write_fault)
return hmm_vma_fault(addr, end, fault, write_fault, walk);
hmm_vma_walk->last = addr;
return hmm_pfns_fill(addr, end, range, HMM_PFN_NONE);
}
static inline uint64_t pmd_to_hmm_pfn_flags(struct hmm_range *range, pmd_t pmd)
@ -221,7 +220,7 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
&fault, &write_fault);
if (fault || write_fault)
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
return hmm_vma_fault(addr, end, fault, write_fault, walk);
pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) {
@ -360,7 +359,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
}
pte_unmap(ptep);
/* Fault any virtual address we were asked to fault */
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
return hmm_vma_fault(addr, end, fault, write_fault, walk);
}
static int hmm_vma_walk_pmd(pmd_t *pmdp,
@ -512,7 +511,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
cpu_flags, &fault, &write_fault);
if (fault || write_fault) {
spin_unlock(ptl);
return hmm_vma_walk_hole_(addr, end, fault, write_fault,
return hmm_vma_fault(addr, end, fault, write_fault,
walk);
}
@ -572,7 +571,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
&fault, &write_fault);
if (fault || write_fault) {
spin_unlock(ptl);
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
return hmm_vma_fault(addr, end, fault, write_fault, walk);
}
pfn = pte_pfn(entry) + ((start & ~hmask) >> PAGE_SHIFT);