io-mapping: indicate mapping failure

The !ATOMIC_IOMAP version of io_maping_init_wc will always return
success, even when the ioremap fails.

Since the ATOMIC_IOMAP version returns NULL when the init fails, and
callers check for a NULL return on error this is unexpected.

During a device probe, where the ioremap failed, a crash can look like
this:

    BUG: unable to handle page fault for address: 0000000000210000
     #PF: supervisor write access in kernel mode
     #PF: error_code(0x0002) - not-present page
     Oops: 0002 [#1] PREEMPT SMP
     CPU: 0 PID: 177 Comm:
     RIP: 0010:fill_page_dma [i915]
       gen8_ppgtt_create [i915]
       i915_ppgtt_create [i915]
       intel_gt_init [i915]
       i915_gem_init [i915]
       i915_driver_probe [i915]
       pci_device_probe
       really_probe
       driver_probe_device

The remap failure occurred much earlier in the probe.  If it had been
propagated, the driver would have exited with an error.

Return NULL on ioremap failure.

[[email protected]: detect ioremap_wc() errors earlier]

Fixes: cafaf14a5d8f ("io-mapping: Always create a struct to hold metadata about the io-mapping")
Signed-off-by: Michael J. Ruhl <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
index 0beaa3eba15516d53d149a89e2a562313ef8d243..c75e4d3d8833fd0f77f0e61ca1014826afdf63bc 100644 (file)
--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -107,9 +107,12 @@ io_mapping_init_wc(struct io_mapping *iomap,
                   resource_size_t base,
                   unsigned long size)
 {
+       iomap->iomem = ioremap_wc(base, size);
+       if (!iomap->iomem)
+               return NULL;
+
        iomap->base = base;
        iomap->size = size;
-       iomap->iomem = ioremap_wc(base, size);
 #if defined(pgprot_noncached_wc) /* archs can't agree on a name ... */
        iomap->prot = pgprot_noncached_wc(PAGE_KERNEL);
 #elif defined(pgprot_writecombine)