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-rw-r--r--mm/hugetlb.c50
1 files changed, 15 insertions, 35 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 01f3e36caa6c..0ad53ad98e74 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6687,10 +6687,11 @@ static unsigned long page_table_shareable(struct vm_area_struct *svma,
return saddr;
}
-static bool __vma_aligned_range_pmd_shareable(struct vm_area_struct *vma,
- unsigned long start, unsigned long end,
- bool check_vma_lock)
+bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr)
{
+ unsigned long start = addr & PUD_MASK;
+ unsigned long end = start + PUD_SIZE;
+
#ifdef CONFIG_USERFAULTFD
if (uffd_disable_huge_pmd_share(vma))
return false;
@@ -6700,38 +6701,13 @@ static bool __vma_aligned_range_pmd_shareable(struct vm_area_struct *vma,
*/
if (!(vma->vm_flags & VM_MAYSHARE))
return false;
- if (check_vma_lock && !vma->vm_private_data)
+ if (!vma->vm_private_data) /* vma lock required for sharing */
return false;
if (!range_in_vma(vma, start, end))
return false;
return true;
}
-static bool vma_pmd_shareable(struct vm_area_struct *vma)
-{
- unsigned long start = ALIGN(vma->vm_start, PUD_SIZE),
- end = ALIGN_DOWN(vma->vm_end, PUD_SIZE);
-
- if (start >= end)
- return false;
-
- return __vma_aligned_range_pmd_shareable(vma, start, end, false);
-}
-
-static bool vma_addr_pmd_shareable(struct vm_area_struct *vma,
- unsigned long addr)
-{
- unsigned long start = addr & PUD_MASK;
- unsigned long end = start + PUD_SIZE;
-
- return __vma_aligned_range_pmd_shareable(vma, start, end, true);
-}
-
-bool want_pmd_share(struct vm_area_struct *vma, unsigned long addr)
-{
- return vma_addr_pmd_shareable(vma, addr);
-}
-
/*
* Determine if start,end range within vma could be mapped by shared pmd.
* If yes, adjust start and end to cover range associated with possible
@@ -6880,17 +6856,21 @@ static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma)
if (vma->vm_private_data)
return;
- /* Check size/alignment for pmd sharing possible */
- if (!vma_pmd_shareable(vma))
- return;
-
vma_lock = kmalloc(sizeof(*vma_lock), GFP_KERNEL);
- if (!vma_lock)
+ if (!vma_lock) {
/*
* If we can not allocate structure, then vma can not
- * participate in pmd sharing.
+ * participate in pmd sharing. This is only a possible
+ * performance enhancement and memory saving issue.
+ * However, the lock is also used to synchronize page
+ * faults with truncation. If the lock is not present,
+ * unlikely races could leave pages in a file past i_size
+ * until the file is removed. Warn in the unlikely case of
+ * allocation failure.
*/
+ pr_warn_once("HugeTLB: unable to allocate vma specific lock\n");
return;
+ }
kref_init(&vma_lock->refs);
init_rwsem(&vma_lock->rw_sema);