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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2017-04-13 14:56:17 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-12-16 10:33:50 +0100
commitd4443b53732e5e98220ec8777d11e3c9eb87f5fd (patch)
treeaba2acb26f17746e9edd58803852a200c6eb9840 /mm/huge_memory.c
parent696fbe191acd2809e2e8b385b455845cf0a18887 (diff)
thp: reduce indentation level in change_huge_pmd()
commit 0a85e51d37645e9ce57e5e1a30859e07810ed07c upstream. Patch series "thp: fix few MADV_DONTNEED races" For MADV_DONTNEED to work properly with huge pages, it's critical to not clear pmd intermittently unless you hold down_write(mmap_sem). Otherwise MADV_DONTNEED can miss the THP which can lead to userspace breakage. See example of such race in commit message of patch 2/4. All these races are found by code inspection. I haven't seen them triggered. I don't think it's worth to apply them to stable@. This patch (of 4): Restructure code in preparation for a fix. Link: http://lkml.kernel.org/r/20170302151034.27829-2-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [jwang: adjust context for 4.4 kernel] Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r--mm/huge_memory.c50
1 files changed, 26 insertions, 24 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8f3769ec8575..ea013cb2c3f2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1566,35 +1566,37 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
{
struct mm_struct *mm = vma->vm_mm;
spinlock_t *ptl;
+ pmd_t entry;
+ bool preserve_write;
+
int ret = 0;
- if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
- pmd_t entry;
- bool preserve_write = prot_numa && pmd_write(*pmd);
- ret = 1;
+ if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1)
+ return 0;
- /*
- * Avoid trapping faults against the zero page. The read-only
- * data is likely to be read-cached on the local CPU and
- * local/remote hits to the zero page are not interesting.
- */
- if (prot_numa && is_huge_zero_pmd(*pmd)) {
- spin_unlock(ptl);
- return ret;
- }
+ preserve_write = prot_numa && pmd_write(*pmd);
+ ret = 1;
- if (!prot_numa || !pmd_protnone(*pmd)) {
- entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
- entry = pmd_modify(entry, newprot);
- if (preserve_write)
- entry = pmd_mkwrite(entry);
- ret = HPAGE_PMD_NR;
- set_pmd_at(mm, addr, pmd, entry);
- BUG_ON(!preserve_write && pmd_write(entry));
- }
- spin_unlock(ptl);
- }
+ /*
+ * Avoid trapping faults against the zero page. The read-only
+ * data is likely to be read-cached on the local CPU and
+ * local/remote hits to the zero page are not interesting.
+ */
+ if (prot_numa && is_huge_zero_pmd(*pmd))
+ goto unlock;
+
+ if (prot_numa && pmd_protnone(*pmd))
+ goto unlock;
+ entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
+ entry = pmd_modify(entry, newprot);
+ if (preserve_write)
+ entry = pmd_mkwrite(entry);
+ ret = HPAGE_PMD_NR;
+ set_pmd_at(mm, addr, pmd, entry);
+ BUG_ON(!preserve_write && pmd_write(entry));
+unlock:
+ spin_unlock(ptl);
return ret;
}