hugetlb: add lockdep check for i_mmap_rwsem held in huge_pmd_share

As a debugging aid, huge_pmd_share should make sure i_mmap_rwsem is held
if necessary.  To clarify the 'if necessary', expand the comment block at
the beginning of huge_pmd_share.

No functional change.  The added i_mmap_assert_locked() call is only
enabled if CONFIG_LOCKDEP.

Ideally, this should have been included with commit 34ae204f1851
("hugetlbfs: remove call to huge_pte_alloc without i_mmap_rwsem").

Signed-off-by: Mike Kravetz <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions