mm: hwpoison: dissolve in-use hugepage in unrecoverable memory error

Currently me_huge_page() relies on dequeue_hwpoisoned_huge_page() to
keep the error hugepage away from the system, which is OK but not good
enough because the hugepage still has a refcount and unpoison doesn't
work on the error hugepage (PageHWPoison flags are cleared but pages are
still leaked.) And there's "wasting health subpages" issue too.  This
patch reworks on me_huge_page() to solve these issues.

For hugetlb file, recently we have truncating code so let's use it in
hugetlbfs specific ->error_remove_page().

For anonymous hugepage, it's helpful to dissolve the error page after
freeing it into free hugepage list.  Migration entry and PageHWPoison in
the head page prevent the access to it.

TODO: dissolve_free_huge_page() can fail but we don't considered it yet.
It's not critical (and at least no worse that now) because in such case
the error hugepage just stays in free hugepage list without being
dissolved.  By virtue of PageHWPoison in head page, it's never allocated
to processes.

[akpm@linux-foundation.org: fix unused var warnings]
Fixes: 23a003bfd23ea9ea0b7756b920e51f64b284b468 ("mm/madvise: pass return code of memory_failure() to userspace")
Link: http://lkml.kernel.org/r/20170417055948.GM31394@yexl-desktop
Link: http://lkml.kernel.org/r/1496305019-5493-8-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index d44f545..5238861 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -851,6 +851,16 @@ static int hugetlbfs_migrate_page(struct address_space *mapping,
 	return MIGRATEPAGE_SUCCESS;
 }
 
+static int hugetlbfs_error_remove_page(struct address_space *mapping,
+				struct page *page)
+{
+	struct inode *inode = mapping->host;
+
+	remove_huge_page(page);
+	hugetlb_fix_reserve_counts(inode);
+	return 0;
+}
+
 static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(dentry->d_sb);
@@ -966,6 +976,7 @@ static const struct address_space_operations hugetlbfs_aops = {
 	.write_end	= hugetlbfs_write_end,
 	.set_page_dirty	= hugetlbfs_set_page_dirty,
 	.migratepage    = hugetlbfs_migrate_page,
+	.error_remove_page	= hugetlbfs_error_remove_page,
 };