4.10-rc loadtest (even on x86, even without THPCache) fails with
"fork: Cannot allocate memory" or some such; and /proc/meminfo
shows PageTables growing.
rc1 removed the freeing of an unused preallocated pagetable after
do_fault_around() has called map_pages(): which is usually a good
optimization, so that the followup doesn't have to reallocate one;
but it's not sufficient to shift the freeing into alloc_set_pte(),
since there are failure cases (most commonly VM_FAULT_RETRY) which
never reach finish_fault().
Check and free it at the outer level in do_fault(), then we don't
need to worry in alloc_set_pte(), and can restore that to how it was
(I cannot find any reason to pte_free() under lock as it was doing).
And fix a separate pagetable leak, or crash, introduced by the same
change, that could only show up on some ppc64: why does do_set_pmd()'s
failure case attempt to withdraw a pagetable when it never deposited
one, at the same time overwriting (so leaking) the vmf->prealloc_pte?
Residue of an earlier implementation, perhaps? Delete it.
Fixes: 953c66c2b22a ("mm: THP page cache support for ppc64")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
mm/memory.c | 47 ++++++++++++++++++++---------------------------
1 file changed, 20 insertions(+), 27 deletions(-)
--- 4.10-rc2/mm/memory.c 2016-12-25 18:40:50.830453384 -0800
+++ linux/mm/memory.c 2017-01-07 13:34:29.373381551 -0800
@@ -3008,13 +3008,6 @@ static int do_set_pmd(struct vm_fault *v
ret = 0;
count_vm_event(THP_FILE_MAPPED);
out:
- /*
- * If we are going to fallback to pte mapping, do a
- * withdraw with pmd lock held.
- */
- if (arch_needs_pgtable_deposit() && ret == VM_FAULT_FALLBACK)
- vmf->prealloc_pte = pgtable_trans_huge_withdraw(vma->vm_mm,
- vmf->pmd);
spin_unlock(vmf->ptl);
return ret;
}
@@ -3055,20 +3048,18 @@ int alloc_set_pte(struct vm_fault *vmf,
ret = do_set_pmd(vmf, page);
if (ret != VM_FAULT_FALLBACK)
- goto fault_handled;
+ return ret;
}
if (!vmf->pte) {
ret = pte_alloc_one_map(vmf);
if (ret)
- goto fault_handled;
+ return ret;
}
/* Re-check under ptl */
- if (unlikely(!pte_none(*vmf->pte))) {
- ret = VM_FAULT_NOPAGE;
- goto fault_handled;
- }
+ if (unlikely(!pte_none(*vmf->pte)))
+ return VM_FAULT_NOPAGE;
flush_icache_page(vma, page);
entry = mk_pte(page, vma->vm_page_prot);
@@ -3088,15 +3079,8 @@ int alloc_set_pte(struct vm_fault *vmf,
/* no need to invalidate: a not-present page won't be cached */
update_mmu_cache(vma, vmf->address, vmf->pte);
- ret = 0;
-fault_handled:
- /* preallocated pagetable is unused: free it */
- if (vmf->prealloc_pte) {
- pte_free(vmf->vma->vm_mm, vmf->prealloc_pte);
- vmf->prealloc_pte = 0;
- }
- return ret;
+ return 0;
}
@@ -3360,15 +3344,24 @@ static int do_shared_fault(struct vm_fau
static int do_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
+ int ret;
/* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */
if (!vma->vm_ops->fault)
- return VM_FAULT_SIGBUS;
- if (!(vmf->flags & FAULT_FLAG_WRITE))
- return do_read_fault(vmf);
- if (!(vma->vm_flags & VM_SHARED))
- return do_cow_fault(vmf);
- return do_shared_fault(vmf);
+ ret = VM_FAULT_SIGBUS;
+ else if (!(vmf->flags & FAULT_FLAG_WRITE))
+ ret = do_read_fault(vmf);
+ else if (!(vma->vm_flags & VM_SHARED))
+ ret = do_cow_fault(vmf);
+ else
+ ret = do_shared_fault(vmf);
+
+ /* preallocated pagetable is unused: free it */
+ if (vmf->prealloc_pte) {
+ pte_free(vma->vm_mm, vmf->prealloc_pte);
+ vmf->prealloc_pte = 0;
+ }
+ return ret;
}
static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
--
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