Thread (49 messages) 49 messages, 4 authors, 2015-03-23

Re: [PATCH 1/4] mm: thp: Return the correct value for change_huge_pmd

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: 2015-03-07 20:13:30
Also in: linux-mm, linux-xfs, lkml

Looks obviously correct. The old code was just very wrong.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>

                     Linus


On Sat, Mar 7, 2015 at 7:20 AM, Mel Gorman [off-list ref] wrote:
quoted hunk ↗ jump to hunk
The wrong value is being returned by change_huge_pmd since commit
10c1045f28e8 ("mm: numa: avoid unnecessary TLB flushes when setting
NUMA hinting entries") which allows a fallthrough that tries to adjust
non-existent PTEs. This patch corrects it.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 mm/huge_memory.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index fc00c8cb5a82..194c0f019774 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1482,6 +1482,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,

        if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
                pmd_t entry;
+               ret = 1;

                /*
                 * Avoid trapping faults against the zero page. The read-only
@@ -1490,11 +1491,10 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
                 */
                if (prot_numa && is_huge_zero_pmd(*pmd)) {
                        spin_unlock(ptl);
-                       return 0;
+                       return ret;
                }

                if (!prot_numa || !pmd_protnone(*pmd)) {
-                       ret = 1;
                        entry = pmdp_get_and_clear_notify(mm, addr, pmd);
                        entry = pmd_modify(entry, newprot);
                        ret = HPAGE_PMD_NR;
--
2.1.2
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