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mm/hmm: make hmm_range_fault return 0 or -1

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hmm_vma_walk->last is supposed to be updated after every write to the
pfns, so that it can be returned by hmm_range_fault(). However, this is
not done consistently. Fortunately nothing checks the return code of
hmm_range_fault() for anything other than error.

More importantly last must be set before returning -EBUSY as it is used to
prevent reading an output pfn as an input flags when the loop restarts.

For clarity and simplicity make hmm_range_fault() return 0 or -ERRNO. Only
set last when returning -EBUSY.

Link: https://lore.kernel.org/r/2-v2-b4e84f444c7d+24f57-hmm_no_flags_jgg@mellanox.com
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Tested-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2020-05-01 15:20:45 -03:00
parent 0e698dfa28
commit be957c886d
5 changed files with 16 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/vm/hmm.rst
View File

@ -161,7 +161,7 @@ device must complete the update before the driver callback returns.
When the device driver wants to populate a range of virtual addresses, it can
use::
long hmm_range_fault(struct hmm_range *range);
int hmm_range_fault(struct hmm_range *range);
It will trigger a page fault on missing or read-only entries if write access is
requested (see below). Page faults use the generic mm page fault code path just

4
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
View File

@ -852,12 +852,12 @@ retry:
down_read(&mm->mmap_sem);
r = hmm_range_fault(range);
up_read(&mm->mmap_sem);
if (unlikely(r <= 0)) {
if (unlikely(r)) {
/*
* FIXME: This timeout should encompass the retry from
* mmu_interval_read_retry() as well.
*/
if ((r == 0 || r == -EBUSY) && !time_after(jiffies, timeout))
if (r == -EBUSY && !time_after(jiffies, timeout))
goto retry;
goto out_free_pfns;
}

6
drivers/gpu/drm/nouveau/nouveau_svm.c
View File

@ -536,7 +536,7 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
.pfn_shift = NVIF_VMM_PFNMAP_V0_ADDR_SHIFT,
};
struct mm_struct *mm = notifier->notifier.mm;
long ret;
int ret;
while (true) {
if (time_after(jiffies, timeout))
@ -548,8 +548,8 @@ static int nouveau_range_fault(struct nouveau_svmm *svmm,
down_read(&mm->mmap_sem);
ret = hmm_range_fault(&range);
up_read(&mm->mmap_sem);
if (ret <= 0) {
if (ret == 0 || ret == -EBUSY)
if (ret) {
if (ret == -EBUSY)
continue;
return ret;
}

2
include/linux/hmm.h
View File

@ -120,7 +120,7 @@ static inline struct page *hmm_device_entry_to_page(const struct hmm_range *rang
/*
* Please see Documentation/vm/hmm.rst for how to use the range API.
*/
long hmm_range_fault(struct hmm_range *range);
int hmm_range_fault(struct hmm_range *range);
/*
* HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range

25
mm/hmm.c
View File

@ -174,7 +174,6 @@ static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
}
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);
}
@ -207,7 +206,6 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags;
hmm_vma_walk->last = end;
return 0;
}
#else /* CONFIG_TRANSPARENT_HUGEPAGE */
@ -386,13 +384,10 @@ again:
r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, pfns);
if (r) {
/* hmm_vma_handle_pte() did pte_unmap() */
hmm_vma_walk->last = addr;
return r;
}
}
pte_unmap(ptep - 1);
hmm_vma_walk->last = addr;
return 0;
}
@ -455,7 +450,6 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
for (i = 0; i < npages; ++i, ++pfn)
pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
cpu_flags;
hmm_vma_walk->last = end;
goto out_unlock;
}
@ -500,7 +494,6 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
cpu_flags;
hmm_vma_walk->last = end;
spin_unlock(ptl);
return 0;
}
@ -537,7 +530,6 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
return -EFAULT;
hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
hmm_vma_walk->last = end;
/* Skip this vma and continue processing the next vma. */
return 1;
@ -555,9 +547,7 @@ static const struct mm_walk_ops hmm_walk_ops = {
* hmm_range_fault - try to fault some address in a virtual address range
* @range: argument structure
*
* Return: the number of valid pages in range->pfns[] (from range start
* address), which may be zero. On error one of the following status codes
* can be returned:
* Returns 0 on success or one of the following error codes:
*
* -EINVAL: Invalid arguments or mm or virtual address is in an invalid vma
* (e.g., device file vma).
@ -572,7 +562,7 @@ static const struct mm_walk_ops hmm_walk_ops = {
* This is similar to get_user_pages(), except that it can read the page tables
* without mutating them (ie causing faults).
*/
long hmm_range_fault(struct hmm_range *range)
int hmm_range_fault(struct hmm_range *range)
{
struct hmm_vma_walk hmm_vma_walk = {
.range = range,
@ -590,10 +580,13 @@ long hmm_range_fault(struct hmm_range *range)
return -EBUSY;
ret = walk_page_range(mm, hmm_vma_walk.last, range->end,
&hmm_walk_ops, &hmm_vma_walk);
/*
* When -EBUSY is returned the loop restarts with
* hmm_vma_walk.last set to an address that has not been stored
* in pfns. All entries < last in the pfn array are set to their
* output, and all >= are still at their input values.
*/
} while (ret == -EBUSY);
if (ret)
return ret;
return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
return ret;
}
EXPORT_SYMBOL(hmm_range_fault);