Commit 4f16fc10 authored by Naoya Horiguchi's avatar Naoya Horiguchi Committed by Linus Torvalds
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mm: hugetlb: fix hugepage memory leak in mincore()



Most callers of pmd_none_or_clear_bad() check whether the target page is
in a hugepage or not, but mincore() and walk_page_range() do not check it.
 So if we use mincore() on a hugepage on x86 machine, the hugepage memory
is leaked as shown below.  This patch fixes it by extending mincore()
system call to support hugepages.

Details
=======
My test program (leak_mincore) works as follows:
 - creat() and mmap() a file on hugetlbfs (file size is 200MB == 100 hugepages,)
 - read()/write() something on it,
 - call mincore() for first ten pages and printf() the values of *vec
 - munmap() and unlink() the file on hugetlbfs

Without my patch
----------------
$ cat /proc/meminfo| grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ./leak_mincore
vec[0] 0
vec[1] 0
vec[2] 0
vec[3] 0
vec[4] 0
vec[5] 0
vec[6] 0
vec[7] 0
vec[8] 0
vec[9] 0
$ cat /proc/meminfo |grep "HugePage"
HugePages_Total:    1000
HugePages_Free:      999
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ls /hugetlbfs/
$

Return values in *vec from mincore() are set to 0, while the hugepage
should be in memory, and 1 hugepage is still accounted as used while
there is no file on hugetlbfs.

With my patch
-------------
$ cat /proc/meminfo| grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ./leak_mincore
vec[0] 1
vec[1] 1
vec[2] 1
vec[3] 1
vec[4] 1
vec[5] 1
vec[6] 1
vec[7] 1
vec[8] 1
vec[9] 1
$ cat /proc/meminfo |grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ls /hugetlbfs/
$

Return value in *vec set to 1 and no memory leaks.

[akpm@linux-foundation.org: cleanup]
[akpm@linux-foundation.org: build fix]
Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: David Rientjes <rientjes@google.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 536240f2
......@@ -14,6 +14,7 @@
#include <linux/syscalls.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/hugetlb.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
......@@ -72,6 +73,42 @@ static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pag
if (!vma || addr < vma->vm_start)
return -ENOMEM;
#ifdef CONFIG_HUGETLB_PAGE
if (is_vm_hugetlb_page(vma)) {
struct hstate *h;
unsigned long nr_huge;
unsigned char present;
i = 0;
nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT);
h = hstate_vma(vma);
nr_huge = ((addr + pages * PAGE_SIZE - 1) >> huge_page_shift(h))
- (addr >> huge_page_shift(h)) + 1;
nr_huge = min(nr_huge,
(vma->vm_end - addr) >> huge_page_shift(h));
while (1) {
/* hugepage always in RAM for now,
* but generally it needs to be check */
ptep = huge_pte_offset(current->mm,
addr & huge_page_mask(h));
present = !!(ptep &&
!huge_pte_none(huge_ptep_get(ptep)));
while (1) {
vec[i++] = present;
addr += PAGE_SIZE;
/* reach buffer limit */
if (i == nr)
return nr;
/* check hugepage border */
if (!((addr & ~huge_page_mask(h))
>> PAGE_SHIFT))
break;
}
}
return nr;
}
#endif
/*
* Calculate how many pages there are left in the last level of the
* PTE array for our address.
......
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