[PATCH AUTOSEL for 4.15 115/189] fs/dax.c: release PMD lock even when there is no PMD support in DAX

[Sasha Levin]

From: Jan H. SchÃnherr <jschoenh@xxxxxxxxx>

[ Upstream commit ee190ca6516bc8257e3d36187ca6f0f71a9ec477 ]

follow_pte_pmd() can theoretically return after having acquired a PMD
lock, even when DAX was not compiled with CONFIG_FS_DAX_PMD.

Release the PMD lock unconditionally.

Link: http://lkml.kernel.org/r/20180118133839.20587-1-jschoenh@xxxxxxxxx
Fixes: f729c8c9b24f ("dax: wrprotect pmd_t in dax_mapping_entry_mkclean")
Signed-off-by: Jan H. SchÃnherr <jschoenh@xxxxxxxxx>
Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 fs/dax.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dax.c b/fs/dax.c
index 95981591977a..c2ebf10b70da 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -636,8 +636,8 @@ static void dax_mapping_entry_mkclean(struct address_space *mapping,
 			pmd = pmd_mkclean(pmd);
 			set_pmd_at(vma->vm_mm, address, pmdp, pmd);
 unlock_pmd:
-			spin_unlock(ptl);
 #endif
+			spin_unlock(ptl);
 		} else {
 			if (pfn != pte_pfn(*ptep))
 				goto unlock_pte;
-- 
2.15.1