powerpc: allow pte_offset_map[_lock]() to fail

In rare transient cases, not yet made possible, pte_offset_map() and
pte_offset_map_lock() may not find a page table: handle appropriately.
Balance successful pte_offset_map() with pte_unmap() where omitted.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Hugh Dickins <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Cc: Alexandre Ghiti <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: Claudio Imbrenda <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: John David Anglin <[email protected]>
Cc: John Paul Adrian Glaubitz <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Mike Rapoport (IBM) <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Qi Zheng <[email protected]>
Cc: Russell King <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 728d3c257e4a..69447bdf0bcf 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3376,12 +3376,15 @@ static void show_pte(unsigned long addr)
 	printf("pmdp @ 0x%px = 0x%016lx\n", pmdp, pmd_val(*pmdp));
 
 	ptep = pte_offset_map(pmdp, addr);
-	if (pte_none(*ptep)) {
+	if (!ptep || pte_none(*ptep)) {
+		if (ptep)
+			pte_unmap(ptep);
 		printf("no valid PTE\n");
 		return;
 	}
 
 	format_pte(ptep, pte_val(*ptep));
+	pte_unmap(ptep);
 
 	sync();
 	__delay(200);