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: Naoya 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/mm/mincore.c b/mm/mincore.c
index 8cb508f84ea4..7a3436ef39eb 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -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.