Commit f8c888a3 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jason Gunthorpe
Browse files

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: 2aee09d8 ("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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 45050692

mm/hmm.c

+18 −19
Original line number Diff line number Diff line
@@ -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;



			ret = hmm_vma_do_fault(walk, addr, write_fault,

					       &pfns[i]);

		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 @@ fault: 
	}

	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);

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