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forked fromtorvalds/linux

Commit0a85e51

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kiryltorvalds
authored andcommitted
thp: reduce indentation level in change_huge_pmd()
Patch series "thp: fix few MADV_DONTNEED races"For MADV_DONTNEED to work properly with huge pages, it's critical to notclear pmd intermittently unless you hold down_write(mmap_sem).Otherwise MADV_DONTNEED can miss the THP which can lead to userspacebreakage.See example of such race in commit message of patch 2/4.All these races are found by code inspection. I haven't seen themtriggered. 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.comSigned-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>
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‎mm/huge_memory.c‎

Lines changed: 26 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -1724,37 +1724,37 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
17241724
{
17251725
structmm_struct*mm=vma->vm_mm;
17261726
spinlock_t*ptl;
1727-
intret=0;
1727+
pmd_tentry;
1728+
boolpreserve_write;
1729+
intret;
17281730

17291731
ptl=__pmd_trans_huge_lock(pmd,vma);
1730-
if (ptl) {
1731-
pmd_tentry;
1732-
boolpreserve_write=prot_numa&&pmd_write(*pmd);
1733-
ret=1;
1732+
if (!ptl)
1733+
return0;
17341734

1735-
/*
1736-
* Avoid trapping faults against the zero page. The read-only
1737-
* data is likely to be read-cached on the local CPU and
1738-
* local/remote hits to the zero page are not interesting.
1739-
*/
1740-
if (prot_numa&&is_huge_zero_pmd(*pmd)) {
1741-
spin_unlock(ptl);
1742-
returnret;
1743-
}
1735+
preserve_write=prot_numa&&pmd_write(*pmd);
1736+
ret=1;
17441737

1745-
if (!prot_numa|| !pmd_protnone(*pmd)) {
1746-
entry=pmdp_huge_get_and_clear_notify(mm,addr,pmd);
1747-
entry=pmd_modify(entry,newprot);
1748-
if (preserve_write)
1749-
entry=pmd_mk_savedwrite(entry);
1750-
ret=HPAGE_PMD_NR;
1751-
set_pmd_at(mm,addr,pmd,entry);
1752-
BUG_ON(vma_is_anonymous(vma)&& !preserve_write&&
1753-
pmd_write(entry));
1754-
}
1755-
spin_unlock(ptl);
1756-
}
1738+
/*
1739+
* Avoid trapping faults against the zero page. The read-only
1740+
* data is likely to be read-cached on the local CPU and
1741+
* local/remote hits to the zero page are not interesting.
1742+
*/
1743+
if (prot_numa&&is_huge_zero_pmd(*pmd))
1744+
gotounlock;
17571745

1746+
if (prot_numa&&pmd_protnone(*pmd))
1747+
gotounlock;
1748+
1749+
entry=pmdp_huge_get_and_clear_notify(mm,addr,pmd);
1750+
entry=pmd_modify(entry,newprot);
1751+
if (preserve_write)
1752+
entry=pmd_mk_savedwrite(entry);
1753+
ret=HPAGE_PMD_NR;
1754+
set_pmd_at(mm,addr,pmd,entry);
1755+
BUG_ON(vma_is_anonymous(vma)&& !preserve_write&&pmd_write(entry));
1756+
unlock:
1757+
spin_unlock(ptl);
17581758
returnret;
17591759
}
17601760

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