From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: mm: hugetlb: fix copy_hugetlb_page_range()
commit 4a705fef98 ("hugetlb: fix copy_hugetlb_page_range() to handle
migration/hwpoisoned entry") changed the order of
huge_ptep_set_wrprotect() and huge_ptep_get(), which leads to break some
workload like hugepage-backed heap allocation via libhugetlbfs. This
patch fixes it.
The test program for the problem is shown below:
$ cat heap.c
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#define HPS 0x200000
int main() {
int i;
char *p = malloc(HPS);
memset(p, '1', HPS);
for (i = 0; i < 5; i++) {
if (!fork()) {
memset(p, '2', HPS);
p = malloc(HPS);
memset(p, '3', HPS);
free(p);
return 0;
}
}
sleep(1);
free(p);
return 0;
}
$ export HUGETLB_MORECORE=yes ; export HUGETLB_NO_PREFAULT= ; hugectl --heap ./heap
Fixes 4a705fef98 ("hugetlb: fix copy_hugetlb_page_range() to handle
migration/hwpoisoned entry"), so is applicable to -stable kernels which
include it.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Reported-by: Guillaume Morin <guillaume@xxxxxxxxxxx>
Suggested-by: Guillaume Morin <guillaume@xxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [2.6.37+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 1 +
1 file changed, 1 insertion(+)
diff -puN mm/hugetlb.c~mm-hugetlb-fix-copy_hugetlb_page_range-re-new-copy_hugetlb_page_range-causing-crashes mm/hugetlb.c
--- a/mm/hugetlb.c~mm-hugetlb-fix-copy_hugetlb_page_range-re-new-copy_hugetlb_page_range-causing-crashes
+++ a/mm/hugetlb.c
@@ -2604,6 +2604,7 @@ int copy_hugetlb_page_range(struct mm_st
} else {
if (cow)
huge_ptep_set_wrprotect(src, addr, src_pte);
+ entry = huge_ptep_get(src_pte);
ptepage = pte_page(entry);
get_page(ptepage);
page_dup_rmap(ptepage);
_
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