fs/hugetlbfs/inode.c: fix hwpoison reserve accounting

BugLink: http://bugs.launchpad.net/bugs/1731971
commit ab615a5b879292e83653be60aa82113f7c6f462d upstream.

Calling madvise(MADV_HWPOISON) on a hugetlbfs page will result in bad
(negative) reserved huge page counts.  This may not happen immediately,
but may happen later when the underlying file is removed or filesystem
unmounted.  For example:

  AnonHugePages:         0 kB
  ShmemHugePages:        0 kB
  HugePages_Total:       1
  HugePages_Free:        0
  HugePages_Rsvd:    18446744073709551615
  HugePages_Surp:        0
  Hugepagesize:       2048 kB

In routine hugetlbfs_error_remove_page(), hugetlb_fix_reserve_counts is
called after remove_huge_page.  hugetlb_fix_reserve_counts is designed
to only be called/used only if a failure is returned from
hugetlb_unreserve_pages.  Therefore, call hugetlb_unreserve_pages as
required and only call hugetlb_fix_reserve_counts in the unlikely event
that hugetlb_unreserve_pages returns an error.

Link: http://lkml.kernel.org/r/20171019230007.17043-2-mike.kravetz@oracle.com
Fixes: 78bb920344b8 ("mm: hwpoison: dissolve in-use hugepage in unrecoverable memory error")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 28d2753be09498769282facb66593c95b91f498a..a9e3b26e1b720bc80d381264bf6be10b4a318b30 100644 (file)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -855,9 +855,12 @@ static int hugetlbfs_error_remove_page(struct address_space *mapping,
                                struct page *page)
 {
        struct inode *inode = mapping->host;
+       pgoff_t index = page->index;
 
        remove_huge_page(page);
-       hugetlb_fix_reserve_counts(inode);
+       if (unlikely(hugetlb_unreserve_pages(inode, index, index + 1, 1)))
+               hugetlb_fix_reserve_counts(inode);
+
        return 0;
 }