Patch "fs/hugetlbfs/inode.c: fix hwpoison reserve accounting" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fs-hugetlbfs-inode.c-fix-hwpoison-reserve-accounting.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mike Kravetz <[email protected]>
Date: Thu, 2 Nov 2017 15:59:41 -0700
Subject: fs/hugetlbfs/inode.c: fix hwpoison reserve accounting

From: Mike Kravetz <[email protected]>

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.

---
 fs/hugetlbfs/inode.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

@@ -855,9 +855,12 @@ static int hugetlbfs_error_remove_page(s
 				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;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/fs-hugetlbfs-inode.c-fix-hwpoison-reserve-accounting.patch queue-4.13/userfaultfd-hugetlbfs-prevent-uffdio_copy-to-fill-beyond-the-end-of-i_size.patch