[PATCH] m68k: mm: Remove check for VM_IO to fix deferred I/O

Geert Uytterhoeven
2022-01-28T17:30:14Z

When an application accesses a mapped frame buffer backed by deferred
I/O, it receives a segmentation fault. Fix this by removing the check
for VM_IO in do_page_fault().

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
This check was never present in a fault handler on any other
architecture than m68k.
Some digging revealed that it was added in v2.1.106, but I couldn't find
an email with a patch adding it. That same kernel version extended the
use of the hwreg_present() helper to HP9000/300, so the check might have
been needed there, perhaps only during development?
The Atari kernel relies heavily on hwreg_present() (both the success and
failure cases), and these still work, at least on ARAnyM.
---
arch/m68k/mm/fault.c | 2 --
1 file changed, 2 deletions(-)

diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
index 1493cf5eac1e7a39..71aa9f6315dc8028 100644
--- a/arch/m68k/mm/fault.c
+++ b/arch/m68k/mm/fault.c
@@ -93,8 +93,6 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
vma = find_vma(mm, address);
if (!vma)
goto map_err;
- if (vma->vm_flags & VM_IO)
- goto acc_err;
if (vma->vm_start <= address)
goto good_area;
if (!(vma->vm_flags & VM_GROWSDOWN))
--
2.25.1