drm/i915/gem: Ignore readonly failures when updating relocs

If the user passes in a readonly reloc[], by the time we notice we have
already committed to modifying the execobjects, or have indeed done so
already. Reporting the failure just compounds the issue as we have no
second pass to fall back to anymore.

"Be damned if you do, and damned if you don't."

Testcase: igt/gem_exec_reloc/readonly
Fixes: 7dc8f11 ("drm/i915/gem: Drop relocation slowpath")
References: fddcd00 ("drm/i915: Force the slow path after a user-write error")
Signed-off-by: Chris Wilson <[email protected]>
Cc: Matthew Auld <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit 97a37c9)
Signed-off-by: Rodrigo Vivi <[email protected]>

Author: ickle

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

@@ -1477,10 +1477,8 @@ static int eb_relocate_vma(struct i915_execbuffer *eb, struct eb_vma *ev)
 				 * can read from this userspace address.
 				 */
 				offset = gen8_canonical_addr(offset & ~UPDATE);
-				if (unlikely(__put_user(offset, &urelocs[r-stack].presumed_offset))) {
-					remain = -EFAULT;
-					goto out;
-				}
+				__put_user(offset,
+					   &urelocs[r - stack].presumed_offset);
 			}
 		} while (r++, --count);
 		urelocs += ARRAY_SIZE(stack);