mm/highmem: Take kmap_high_get() properly into account

kunmap_local() warns when the virtual address to unmap is below
PAGE_OFFSET. This is correct except for the case that the mapping was
obtained via kmap_high_get() because the PKMAP addresses are right below
PAGE_OFFSET.

Cure it by skipping the WARN_ON() when the unmap was handled by
kunmap_high().

Fixes: 298fa1ad5571 ("highmem: Provide generic variant of kmap_atomic*")
Reported-by: vtolkm@googlemail.com
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/87y2j6n8mj.fsf@nanos.tec.linutronix.de

diff --git a/mm/highmem.c b/mm/highmem.c
index 54bd233..78c481a 100644 (file)
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -426,12 +426,15 @@ static inline void *arch_kmap_local_high_get(struct page *page)
 #endif
 
 /* Unmap a local mapping which was obtained by kmap_high_get() */
-static inline void kmap_high_unmap_local(unsigned long vaddr)
+static inline bool kmap_high_unmap_local(unsigned long vaddr)
 {
 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
-       if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP))
+       if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
                kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
+               return true;
+       }
 #endif
+       return false;
 }
 
 static inline int kmap_local_calc_idx(int idx)
@@ -491,10 +494,14 @@ void kunmap_local_indexed(void *vaddr)
 
        if (addr < __fix_to_virt(FIX_KMAP_END) ||
            addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
-               WARN_ON_ONCE(addr < PAGE_OFFSET);
-
-               /* Handle mappings which were obtained by kmap_high_get() */
-               kmap_high_unmap_local(addr);
+               /*
+                * Handle mappings which were obtained by kmap_high_get()
+                * first as the virtual address of such mappings is below
+                * PAGE_OFFSET. Warn for all other addresses which are in
+                * the user space part of the virtual address space.
+                */
+               if (!kmap_high_unmap_local(addr))
+                       WARN_ON_ONCE(addr < PAGE_OFFSET);
                return;
        }